February at the JC Raulston Arboretum

This post is 2 of 12 of a series I’m doing this year reflecting back on some of my favorite plants from visiting the JC Raulston Arboretum while attending graduate school at NC State in Raleigh NC. Check back next month for more.

February was one of my favorite times to visit the JC Raulston Arboretum. With the hold of winter receding, walking around the garden was a scavenger hunt in discovering what flowers were in bloom. Even the smallest of flowers were appreciated as the gardening season began to awaken. After visiting for a few years, I became more aware of the flowering schedules and knew better what to expect. Sometimes plants would bloom early, sometimes they would flower late, but February seemed to always be a reliable time to start seeing color increasing in the garden.

For this month’s reflections from the JC Raulston Arboretum, I wanted to share some of my favorites for late winter color. Reviewing these photographs reminds me of how many of these plants I actually need to try in Texas!

I enjoyed studying the Prunus mume collection in the garden. Even going back to J.C.’s first newsletter, he spoke highly of them. This cultivar is ‘Bridal Veil’, a really nice weeping form.

A close up of ‘Bridal Veil’ flowers

Close to the stairs of the Ruby McSwain Visitor Center was ‘Omoi-no-mama’, a nice white-to-blush, semi-double flowering form of Prunus mume. I really liked the placement and how walking up the stairs allowed me to get my face in the flowers.

The arboretum had a few specimens of the winter flowering Cornus officinalis and Cornus mas. In the winter garden was ‘Kintoki’, one of my favorite forms of Cornus officinalis selected by Barry Yinger for its beautiful exfoliating bark.

Near ‘Kintoki’ in the winter garden was Chaenomeles speciosa ‘Contorta’. It was a scraggly thing with its contorted flowers, but getting up close with the blooms I made an amazing discovery.

Even the stamens were contorted! How cool! Whatever genes were making the branches bend also curled the flower stamens. I noticed that the sun was about to shine on the blossoms, so I hung around and got a good progress photograph of sunlight hitting the flower. I use these images in my classes to illustrate how light can change the appearance of flowers.

Here is a minute later when the sun barely began to shine on the flowers producing a nice glow. This diffused light shot is my favorite of the three.

And, here another minute later the light is a bit harsher.

Another genera that I fell in love with at the JC Raulston Arboretum was Stachyurus. Here we see ‘Sterling Silver’ wearing its strings of pearls. I can’t believe I haven’t tried these yet in Texas!

Perennials would also start popping around this time of year. I always enjoyed seeing this large planting of the aptly named Narcissus ‘February Gold.’

Most people are familiar with the yellow form of Narcissus pseudonarcissus, but I always thought that these cream Narcissus pseudonarcissus subsp. moschatus looked charming in the perennial border.

I would lay on the ground to photograph Ipheion that barely rose six inches of out the soil. It is like someone stenciled black lines on the undersides of the petals of this ‘Wisley Blue’.

Now I appreciate Ipheion even more as they are one of the few early geophytes that we have flowering in east Texas this time of year. Some like ‘Froyle Mill’ have a really nice purple color.

Iris unguicularis was another reliable winter flowering perennial. It is unfortunate that the flowers are so hidden.

So, you have to get into the clump of Iris unguicularis to really appreciate the flower intricacies.

Another iris in bloom was Iris tuberosa (or Hermodactylus tuberosus), a really novel perennial. Finding a plant with green and black flowers in February is so funky.

Here’s a close up of the flowers on Iris tuberosa. The black falls seem like velvet.

I also enjoyed seeing the spiraling Euphorbia rigida on the roof garden of the Ruby McSwain Visitor Center. The leaves and flowers had such psychedelic colors for late winter.

Walking around one afternoon, I noticed that this plant had flowers in the middle of the leaves! Turns out these “leaves” are actually flattened stems or cladodes on Ruscus × microglossus.

A close up of the quirky Ruscus × microglossus. Students really find these plants fascinating because of the position of the flowers.

A Cold Week in Texas

At 7:24 AM on February 16, our thermometer here in east Texas read -6F. Back home in Tennessee, I’ve walked out in 0F when the moonlight made our snow covered fields glow as if it were day, I’ve flown into Boston to present in between two snowstorms that year the snow didn’t melt until July, and I even spoke the day after the frigid polar vortex descended on Chicago. But, this is the coldest temperature I’ve ever experienced in my life. It is also funny to note that this is the most southern place I’ve ever lived. We’ve had a winter trifecta hit us this week— 6 inches of snow Monday morning, followed by extreme record breaking cold Tuesday morning, and then an ice storm on Wednesday. At one point the whole state of Texas—all 254 counties—was under a winter storm warning.

We have been mostly fine through this insane weather event so far, and I appreciate the messages from readers and friends checking in on us. We had power on and off until Wednesday at noon went it went off and water until Thursday night due to the water company. My heart breaks, though, for those who have been through worse times this week (you can learn more about helping here and here).

But, who would have ever thought we would hit -6F? The airport registered -3F, so I believe my reading in our little valley homestead. The coldest I’ve measured here at the house before this week is 11F. It even drove Dark-eyed Juncos south to our feeder, my first observation of them here at our house.

These temperatures have made me think about plant hardiness. Hardiness is of course a measure of a plant’s survival based on the average annual extreme minimum temperature. Nacogdoches is located in USDA Hardiness Zone 8b, where on average our minimum winter temperature is 15 to 20F. Just after midnight on the 16th, we were at 0F, which means that for 7-to-8 hours we were basically USDA Hardiness Zone 6 (-10F to 0F), which occurs in the panhandle of Texas, the Kentucky/Ohio border, and on the coast of Maine.

It will be interesting to see what plants survive from this event. As horticulturists we are both horrified and intrigued by the question, “What survived?” These extreme weather events interacting with our plants are opportunities to learn what died and to celebrate what lived.

But, hardiness is not an absolute. It is just a measure that gives us some idea of how the cold can impact plant growth. Cold can affect a plant’s hardiness at three points during winter—an early freeze before the plant has acclimated to winter (17F in November that zapped my Magnolias and citrus a few years ago), an extreme winter temperature minimum (here’s looking at you -6F), or a late freeze that may kill a plant after it has resumed growth, whether that be after the frost free date (like the 2007 April freeze) OR after an extreme warming even in winter.

As we go forward into the next few weeks and months here in the deep south, we will see plants die, especially broad leaf evergreens and tropicals, and some plants live. In some cases the living and the dead may be right next to each other or a short distance away. So, we have to remember that hardiness is a combination of so many factors. Sitting in front of the fire this week scribbling notes down for my weekly blog post, I reviewed the lecture “Untangling the Hardiness Question: What is Hardy and Why?” by Dr. J.C. Raulston included in Bobby Ward’s biography of this incredible horticulturist, Chlorophyll in His Veins. Raulston went through a whole gamut in this lecture he once gave to the North American Rock Garden Society in Seattle, WA in 1995. I wanted to briefly list the factors he discussed below.

• Cold — Gardeners quickly connect cold weather with seeing plants die. Raulston noted that using minimum averages is a complex attempt to simplify the effects of cold on plants. One of my favorite quotes he said was, “I can go into the kitchen and put one hand on a gas flame and the other in the freezer and on average I am very comfortable, but you have problems when you hit those two extremes.” Even the type of cold that manifests matters. For example, convective cold usually occurs because a cold front moves into a region. However, radiative cooling is where heat is lost to the atmosphere on cool nights. The example for radiative cooling that Raulston gave is it may be 38F on the thermometer, but the leaf is 28F. We see this in fall on tomatoes on cool mornings.

• Provenance — Where plants or clones of a particular species originated could have resulted in accumulation of traits that increase (or decrease) survival, just because they are growing in Texas instead of Michigan. They are still the same species, but they have adapted in those areas to the conditions they endure. That is often why growers like to get genetics from nearby or a particular part of the country to grow. But, some species may be hardier than the zone in which they grow. Raulston mentions Magnolia ashei as a great example. This native is found in the panhandle of Florida, but the species is hardy in Chicago. Likely, it is a relic from the last ice age that was pushed south and not able to advance back north.

• Population variation — Even within a population of plants from a single cross between two parents, there may be a wide array of different cold tolerances in individuals.

• Cellular location of freezing — Does freezing occur in the cell? Then, that cell ruptures and death is likely. Does freezing occur in the cell wall? Then, the cell is probably fine, and the tissue will likely live.

• Microclimates — Buildings, stones, pavement, windbreaks, and water may all moderate local temperatures and create microclimates, whether they be warmer or cooler. Until this freeze, we still had ‘Pele’s Smoke’ sugarcane overwintering near our campus greenhouse and starting to put up new growth, and yet it is only hardy in zone 9 and south.

• Snow protection — Snow may protect the bottom of plants, but kill the top. Honestly, I’m hoping for this effect on a number of my plants at home. I noticed our rosemary this morning starting to turn black, but near the base were some hints of green.

• Root hardiness — Can the roots survive the cold spell, even if the top of a plant dies? We really see this difference with plants that are in pots versus in the ground. I moved my container woodies that I haven’t gotten into the ground yet into the garage to protect them. And, I’m hoping that some of my tender perennials make it through because their tops were not exposed (and, their roots were covered with 6 inches of snow!).

• Chilling requirement met — Many woodies have to experience chilling hours to be able to flower, and websites log the hours for different regions. If they have met their requirement, then the cold may damage buds. And, if not, then the plants should be ok. I’m hoping that my peach buds were still tight enough to survive the cold. Time will tell.

• Nutrition — Many experts recommend to stop fertilizing perennials and woodies in late summer and early fall to help them survive. Raulston talked about in this lecture about an experiment where azaleas that were fed all the way up until frost didn’t survive. The plants kept growing actively and didn’t have a chance to shut down. The experimental control azaleas that didn’t get fertilizer at the end of the growing season overwintered just fine.

• Active growth — Is the plant growing? Many plants acclimate based on photoperiod, temperature, or some combination of both. The lack of appropriate acclimating could result in death. Raulston noted that a plant could survive in Siberia at -75F but in active growth die at 25F.

• Summer heat — Some plants like Cercis canadensis var. texensis need summer heat to be able to overwinter well. He mentions how if you grow this in a hot summer, it’s hardy to zone 6, but if grown in the Pacific Northwest, it may only be hard to Zone 8. For other plants, the summer heat drains their sugar load so that they don’t have enough carbohydrates to overwinter.

• Scorch — Scorch occurs when the plant is cold but the sun is shining, and water loss from the leaf is high. I’ve even heard Eliot Coleman say that he thinks that scorch and wind desiccation of plants hurts some winter edibles more than the cold.

So, yes, plants are going to die or be damaged from this extreme cold event, but keep in mind that many of the above factors could nudge them towards death or pull them towards life.

The other question is where do we go from here? How do we respond in our planting to such an event? In Raulston’s talk, he stated that as horticulturists we accept risks, and sometimes we even dare to grow the impossible for pride and glory. He also stated that what would help us assess hardiness would be to have cold measured on a scale of x-year freezes like we have x-year floods. Raulston talked of a 250-year freeze in his lecture when parts of North Carolina dropped to -10F. That way, we can decide whether we want to use certain plants. And, perhaps this risk can be determined when designing or planting by moving up or down a hardiness zone. That way we have stalwarts that can take anything and less reliable plants that are garnishes in a planting with the understanding that we could loose them in a bad year.

So, maybe -6F is a 250 year freeze? Nearby Tyler, TX set an all time low record of -6F, and records date back 138 years to 1883. But, we also have to ask the question was this event a one off or are more events like this coming due to a changing climate? The science isn’t so clear, but a warming arctic could destabilize the cold air at the North Pole and result in more cold entering the United States. On this matter, too, time will tell.

As someone who loves cold, snow, and winter, I am ready for warmer days. It will be interesting to see now what the next flowering plant will be. Much of the Narcissus and Magnolias are zapped. But, the march to spring continues even with this rough week. The temperature will be 60F on Sunday. Which, if we still don’t have power, will be warmer than our house!

Witch Hazels at The Scott Arboretum

I’ve been enamored with witch hazels ever since I realized they were a thing. As a young horticulturist, I was amazed to discover that a species could flower in the dreariest of winter weather.  And, bloom they do, their petals blazing yellow, orange, red, and even purple against a cold winter sky. These pompoms of color warm the heart and say spring is near.  Where I’ve lived in Tennessee and North Carolina, these have been planted in the gardens I knew and visited, but now living in Texas, they are largely absent from the landscape, save for a few native species.

So, I was happy a few years ago when Karen and I travelled to Philadelphia for a business trip in February.  I wanted to show her The Scott Arboretum where I had interned 10 years ago at the time.  (Wow, has it really been that long?)  I had visited this beautiful campus in spring, summer, and fall but never winter.  I was hopeful that the Hamamelis would be in full bloom. The collection features all kinds of Hamamelis vernalis, Hamamelis × intermedia, and Hamamelis mollis.

We made our way through campus as a cold rain diminished and left a dismal sky in its wake. Yet near the Cunningham House, the pale yellow ‘Luna’ glowed. It is considered by some to be one of the lightest forms available. 

The honey colored ‘Luna’

Around the back the short and dense ‘Quasimodo’ echoed the color of the stem colors found in the Cornus planted nearby. It is such a good cultivar for small spaces.

‘Quasimodo’ is such a cutie. It is short and sweet.

The colors on the petals of 'Quasimodo' were echoed by the nearby Cornus alba ‘Bud's Yellow’ (front) and Cornus sanguinea ‘Arctic Sun’ (back).

We continued past Parrish Hall in the center of campus and the long allée of swamp white oaks to find a few witch hazels on the other side just above the famous amphitheater.  ‘Strawberries and Cream’ had this delicious red to yellow fade outward on the petals that mellowed the color.  Also nearby was a young ‘Diane’, one of the best red witch hazels. She still clung to her marcescent coat of leaves, but I found a perfect spot to navigate a photo without the clingy foliage. 

‘Strawberries and Cream’ just looks delectable, doesn’t it?

‘Diane’ is considered one of the best red forms.

I can’t talk about Swarthmore and The Scott Arboretum without showing you the beautiful natural amphitheater with the scattered tulip poplars.

I almost missed my favorite specimen of the day.  On our way to the main collection, I passed by the Clothier courtyard, but with a quick glance back my eyes caught a blob of yellow and I stopped in my tracks.  Espaliered against the north wall of the courtyard in the fragrance garden was Hamamelis mollis ‘Early Bright’.  Reading in Chris Lane's book Witch Hazels, I realized that this cultivar was found at The Scott Arboretum as a chance seedling, and the name was registered by my friend Andrew Bunting who was curator there for many years because it bloomed a few weeks earlier than other Hamamelis mollis forms.  Seeing it espaliered gave me some serious plant lust for wanting to grow witch hazels in east Texas.  Alas, we lack the winter cold that fans their buds into flames.

Clothier Hall. The courtyard is to the right of the bell tower.

My jaw dropped when I saw this incredible espaliered Hamamelis mollis ‘Early Bright’.

This espaliered ‘Early Bright’ was quite large.  Karen helps us get a sense of scale.

Our arrival to the collection proper near the tennis courts was quickly evident as hazes of crimsons, tangerines, and saffrons filled the drab landscape with color.

Hooray! The main witch hazel collection is in bloom!

I was so impressed by the sheer size of the plants.  Most of the time I see young developing witch hazels in gardens, and I had never seen Hamamelis this large.  Two behemoth specimens were ‘Jelena’ and another ‘Early Bright’, this time allowed to grow into its true form.

Ah, what an incredible specimen of ‘Jelena’. I would say this cultivar is one of the best and most popular forms in the US. Sadly, my two-year old plant is about to die here in Texas due to the lack of winter chilling.

Staring at ‘Jelena’ is like looking at a fiery sunset.

And, here is a large ‘Early Bright’ in full flower.

A close up of ‘Early Bright’.

I really like collections like this because it allows one to study the plants and see their growth and seasonal differences. Some like ‘Primavera’, ‘Feuerzauber’, and ‘Wisley Supreme’ were in full bloom while others like ‘Gimborn's Perfume’ and ‘Sunburst’ had yet to flower.

‘Wisley Supreme’ is one of my favorite yellow forms.

Another good red is ‘Feuerzauber’. It tends to grow more vigorously than ‘Diane’

I love seeing the curls in Hamamelis petals like you see here on ‘Primavera’.

‘Red Imp’, a fun named selection of Hamamelis vernalis, held onto its leaves.

Having seen most of the flowering specimens in the collection and with light waning, we left. It was so much fun to visit this collection and get a better idea of which witch hazels deserve more use and attention in gardens. I hope this overview provides a few ideas and inspiration about using witch hazels in your garden.

Winter Sowings

Sowing perennial seed is one of my favorite tasks of winter.  There's so much anticipation wrapped up in this simple practice, even more so than sowing say lettuce or tomato seeds with their quick germination.  Perennial seed, both woody and herbaceous, may take weeks or months before the first hint of green is seen, so even in this waiting there is an air of mystery. My eyes hover over the trays as I search for life, and I find myself wondering if and when.

Many perennials have evolved to use the exposure to wet cold as an indicator for when they should emerge from dormancy and resume growth.  When I teach the concept of this physiological dormancy to students, I liken this period to an alarm clock.  Seeds have to get the appropriate amount of wet chilling time for the maximum number of seeds to germinate (or “wake up”).  Without this exposure, none or only a few may start growing (as far as the few goes, variation does exist within a population!).  This moist chilling results in physiological changes to the embryo that then allow the seed to overcome dormancy. You can hypothesize how this could be selected. Those that emerge early die in the cold. Those that bide their time awake to a glorious spring and can pass on their traits.

The staggered germination of Echinacea sanguinea. Note that there are a few larger ones with two or three true leaves that evidently didn’t need any chilling to enhance germination, but many seeds did and have only their pair of cotyledons. Don’t mind the wavy-leaf Streptanthus on the bottom or the couple of Penstemon tenuis that creeped into this block.

While this method of overcoming of dormancy occurs in nature, we horticulturists call the practice where we expose seeds to cold and moist conditions cold stratification (there is also warm stratification for some seeds, hence the addition the modifier).  Usually the seeds are placed in moistened sand, perlite, vermiculite, peat moss, or some blend of those; I've even used paper towels and coffee filters if they go into the fridge.  Now, mind you, all seeds don’t need this exposure.  Again, I recommend Norman Deno's wonderful online Seed Germination Theory and Practice to investigate the requirements. 

I've always wondered about the etymology of the word stratification. Strata means layers, not seed. Then, I read in Hartmann and Kester’s Plant Propagation: Principles and Practice how nurseries used to make layers of seed that were separated by moist substrate in outdoor pits. These “strata” were allowed to overwinter there.  One of the earliest historical writings about stratification is found in Sylva by John Evelyn in 1664.  I've shared his writing below of how he recommended stratifying, and to save myself from writing "[sic]" every other word, just note that spellings back then were a bit different. 

“Chuse your seed of that which is perfectly mature, ponderous and sound; commonly that which is easily shaken from the boughs, or gathered about November, immediately upon its spontaneous fall, or taken from the tops and summities of the fairest and soundest trees, is best, and does (for the most part) direct to the proper season of interring, according to institution.

Nature herself who all created first,
Invented sowing, and the wild plants nurs’t:
When mast and berries from the trees did drop,
Succeeded under by a numerous crop.

Yet this is to be consider’d, that if the place you sow in be too cold for an autumnal semination, your acorns, mast, and other seeds may be prepared for the vernal by being barrel’d, or potted up in moist sand, or earth stratum super stratum during the winter; ... Chuse a fit piece of ground, and with boards (if it have not that position of it self) design it three foot high; lay the first foot in fine earth, another of seeds, acorns, mast, keys, nuts, haws, holly-berries, &c. promiscuously, or separate, with (now and then) a little mould sprinkled amongst them: The third foot wholly earth: Of these preparatory magazines make as many, and as much larger ones as will serve your turn, continuing it from time to time as your store is brought in. The same for ruder handlings, may you also do by burying your seeds in dry sand, or pulveriz’d earth, barrelling them (as I said) in tubs, or laid in heaps in some deep cellar where the rigour of the winter may least prejudice them; and I have fill’d old hampers, bee-hives, and boxes with them, and found the like advantage, which is to have them ready for your seminary, as before hath been shew’d, and exceedingly prevent the season. ”

Don't you just love the poem in the middle there?

Of course our technique has improved since the 1600's.  In the past I have put the seeds in the fridge, and I have colleagues who also use this cooler method.  But, I like to take advantage of natural winter chilling to germinate seeds.  It is so much easier than bagging seeds up, putting them in the fridge, and then remembering to sow them later on.  Why artificially create what nature already offers?  Also, there is some evidence that the diurnal changes in temperature may positively promote germination. 

Last winter, I filled the cold frame with 4 inches of growing substrate and sowed several different species directly into that media.  We were traveling for the holidays, and I was worried about the seeds drying out too much in individual cells while we were gone. This method worked well.  I got good germination on most species, but sowing en masse made it difficult to separate them when planting up later on. 

The cold frame last winter. Old, used labels that were headed to the trash became block edges for different species.

This year, I sowed the seeds into trays to make it easier on me.  We didn't travel over the holidays, and I was able to more closely monitor their moisture levels.  Because I knew I would run out of room in my cold frame this year, I built a small low tunnel frame where I can cover a 4 × 8 ft area with floating row cover supported by the same hoops I used to cover my vegetable beds.  The floating row cover provides just enough protection to keep the frost off. 

In my rush to get the seeds sown and because a few of them of them still have fluff or chaff on them, I don't fret much about trying to get one seed per hole.  I can always transplant or move seedlings around later in their cells.  I will note that I flame some seed like Liatris, Andropogon, and Asclepias in a bucket to get the fluff off the seed. 

I am fascinated by seeing the differences in germination time, even for some species in the same family.  For example, Penstemon tenuis germinated fairly quickly within a week while Penstemon digitalis took a month from sowing to start showing cotyledons. 

Penstemon digitalis takes longer to germinate than Penstemon tenuis (not pictured).

Winter is a good time to clean out the fridge for seeds and go through old boxes.  I had hoped to be done by now with my winter perennial sowing, but I keep finding more species that I saved earlier this year to sow now.  For most of the country you should still have a little time to get seed that need stratifying sown outdoors or just use the fridge method I mentioned earlier. Either way is sure to result in more plants this year for your garden.

Ipomopsis rubra was another fast germinating species. I transplanted them out shortly after this photo.

Amsonia hubrichtii emerge from their cigar-shaped seed.

The thread-like cotyledons of Lilium formosanum

A Snow Day at the JC Raulston Arboretum

This is post 1 of 12 of a series I’m doing this year reflecting back on some of my favorite plants from visiting the JC Raulston Arboretum while attending graduate school at NC State in Raleigh NC. Check back next month for more.

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It has been seven years since I left graduate school in Raleigh NC. At the time it was a challenge living in an apartment without a garden. Even though I had 100+ plants on my balcony in containers, I missed being able to roam through a garden and observe the minutiae of the day-to-day happenings in the plant world.

The JC Raulston Arboretum became a garden away from my home garden for me. It was started as in 1976 by the late Dr. JC Raulston as a living laboratory for students and the North Carolina nursery industry, and it has blossomed into one of the top university botanic gardens in the United States. (If you want to learn more, read Chlorophyll in His Veins by Bobby Ward). I visited countless times and amassed probably over 10,000 photographs over my time there. So, in what has started as another sedentary year for us with no travel in sight, I’ve decided to plunge into my photographs to share some of my favorite plants each month from this incredible place.

One of my most memorable experiences visiting the arboretum was my first winter in Raleigh. When I left Tennessee to head to North Carolina, I assumed that I would never see snow again. But, in early 2009, 3–7 inches fell on a Tuesday. My official measurement at the arboretum with a ruler was 4 inches.

I remember the day vividly because that Tuesday was January 20, 2009, and Barack Obama was being sworn in as president. Being an independent and political junkie, I had the news going on in the background as I labored on graduate school projects. My desk was right against the window so I would shift screens between the TV, the computer, and glancing up to see the snow flying outside my window. Thinking back now, it was nice to see so much white and peace in a world where red and blue seem to dominate.

Around lunch I headed over to the arboretum once the snow had abated to enjoy the winter wonderland, and I spent at least two hours roaming the collections. Below are some of my favorite photographs and plants of the day.

I loved seeing the screen garden with where the leaves on Agave and Yucca became needles emerging from white pincushions.

You can really appreciate how well the Agave captured snow on this Agave parryi ssp. parryi var. truncata J.C. Raulston’.

I loved seeing how each blade of these Yucca aloifolia were laden with the snow.

The snow highlighted structure of trees. One that was particularly striking was Firmiana simplex. The dull viridian trunk resembled a dinosaur leg.

And, how can you not love this cinnamon-colored bark on Stewartia sinensis var. sinensis?

One plant that I fell in love with the first winter was Salix ‘Flame’, and it is still at the top of my list of favorite plants. I find myself gravitating to colorful stems for winter color, and this orange-twig willow had such a rich, warm hue.

Going through these photographs I realized I had forgotten about Acer negundo ‘White Lightning’! Most consider boxelders trash trees, but wowzer, these stems shine against the white and brown of winter.

And, one cannot forget about the finicky red-twig dogwoods. Here the thin twigs of Cornus sanguinea ‘Midwinter Fire’ glow bright.

In the Japanese garden the black lines of Phyllostachys nigra pop against the white.

The snow adds another dimension to this Tsuga canadensis ‘Curley’. The laden branches look die cut.

The needles of Pinus virginiana ‘Wates Golden’ glow with the afternoon sun.

Osmanthus heterophyllus ‘Goshiki’ was one of my favorite broadleaf evergreens in the garden. The sun-splashed foliage was particularly effective in the winter.

And, then of course were the flowering plants on my snowy visit. Another winter favorite I learned about at the JC Raulston Arboretum was Edgeworthia chrysantha ‘Winter Gold’. At the time paperbushes were fairly unknown, but I would say that their popularity has really grown in the past 10 to 15 years. You can see some flowers opening yellow in this image.

Many members of the witchhazel family flower in winter. Here the buds on the interesting hybrid ×Sycoparrotia semidecidua begin to pop. They are small, but they somewhat resemble exploding figs.

Hamamelis vernalis was also in full bloom on this snowy day and their sweet smell—though some say sickly sweet—perfumed the air.

Looking back I realize just how many of my winter favorites I learned from this garden. Here is Chimonanthus praecox ‘Luteus’. It, too, has an incredible sweet fragrance that can travel far in the garden. Often I smell this shrub before I see it.

Growing up, I always admired the deciduous hollies on the fencerows back in Tennessee. I think they look best with some snowy adornments.

I was tickled pink seeing just how colorful these Symphoricarpos × doorenbosii Magic Berry were.

It is always fun to see how seedheads interact with snow. Here Rudbeckia fulgida ‘Viettes Little Suzi’ appears to be wearing white toboggans.

Serendipity. The syncarps on Liquidambar styraciflua ‘Frosty’ look a little… well… frosty. In case you’re curious about the cultivar name, this selection has variegated leaves.

Even the fading flowers of Schizophragma hydrangeoides ‘Moonlight’ were effective snowcatchers.

Yes, it was a truly memorable day walking through the JC Raulston Arboretum after a good snow. One last photo of the White Garden covered in white. Little did I know at the time that Karen and I would get married here in seven years.

Reflections on Season Extension

I love winter.  Yes, it may seem odd to hear this coming from a horticulturist as with it comes the end of the main growing season, but there is something about the cold, the starkness, and the frost (and potential for snow!!!) that enchants me about this time of year.  In Tennessee where I grew up, this shift in seasons was a bit harsher than it is here in Texas.  But, winter can still have its moments here in zone 8b, too. A few years ago, we experienced 11F, 12F, and 14F three nights in a row.

Even though much of our plant activities are on pause, I like to cheat the these colder months out of a little more with season extension. Extending the growing season for cool season crops relies on two principles, simple, unheated structures + cool-season crops. 

My first forays were simple straw bale cold frames that I saw in gardening books.  I didn't have the means to get glass panes made, so I would get old windows from my family and neighbors nearby to use as a covering.  The straw was good insulation.  It was in these structures that I started my tomatoes and other vegetable transplants. 

One of my first cold frames. You may be wondering about the hog wire. That was used to keep the dogs out.

Eliot Coleman really helped to open my eyes on season extension with his book The New Organic Grower.  In 2014 I built my first ever plastic covered low tunnel in my garden.  I didn't know much about what I was doing.  I used PVC pipe and painters plastic from the hardware store. Within a couple of months, the cover split right down the middle.  But, I was delighted to see that what I was growing in this structure actually worked and that you could continue gardening through the winter in Tennessee.

My first two low tunnels in my garden in 2004.

A rare eight-inch snow event showed me just how sturdy these structures were.

I buried the edges before I realized that sand bags were a thing. It was hard to take the plastic off, and I got down in them and crawled around. It's fun thinking back now about how I got under those covers and scurried around working in my covered beds. 

Fun as it was, the strain on my neck made me want to build something larger.  So, I experimented around next with an A-frame made out of electrical pipe from the local hardware store.  Armed also with more weather resistant plastic, this structure could be walked into, and I did not have to worry about the cover degrading.  I learned about wiggle wire, this simple wire-channel combo that helped to hold plastic down, and I used it on the A-frame end for quick access to my plants.

My A-frame in 2006 after another snowfall.

Inside, mizuna, beets, and spinach are happily growing in the cold.

As my love for season extension grew, I convinced my parents to let me build a small 16 x 24 hoop house at our home in 2008.  Just like the other structures, this greenhouse was unheated and relied on natural heating from the sun. But, it allowed for more experimentation. Inside it was a cold frame; putting protection within protection helped to increase the season extension effect.

Yay! My first greenhouse!!! This snow event was a rare sight in March. You can see the Narcissus foliage on the side poking through the white.

Inside the hoop house, spinach, cabbage, beets, carrots, and more are visible.

Spinach, onions, kale (left, front to back), corn salad, and mache (right, front to back) all survived multiple nights of below freezing temperatures during the 2007-2008 winter.

I decided to track night low temperatures using thermometers over two weeks in January 2008 outside the hoop house, in the hoop house, and under cover, just like the young scientist I was. You can really see the effect of this cold frame in the unheated hoop house in the figure below. While the outdoor low and hoop house low were close to each other most nights, the cold frame temperature registered consistently higher than both of them. One other thing that I’d like to point out is that even with temperatures as low as 8F, crops like spinach still were able to survive in the hoop house with one layer of cover.

The outdoor, hoop house, and cold frame low give a sense of just how cold these plants can tolerate.

However, after winter that I left for grad school, and I had to put my season extension experiments on pause while I lived in an apartment. Now that I have a garden again, I’m back to covering crops during the winter to see just how much I can squeeze out of the growing season. I’ll add that in the six year hiatus the technology has advanced so much. Now with pipe benders you can make hoops out of electrical conduit pipe for around $3 a pipe, and then cover these arcs with floating row cover that lasts for a few seasons if you treat it right.  These permanent hoops are great.  Not only do I use them in the winter, but I also cover squash in the summer to prevent squash vine borer.

My latest iteration on season extension uses bent electrical conduit and floating row cover.

To me, it’s fun to be able to go out in the middle of winter and harvest a salad grown right in my backyard. It is so simple I believe that everyone can do it. So, experiment around with season extension to see just how much can be grown by pushing the limits beyond frost. You’ll be pleasantly surprised

Christmas Cheer at Williamsburg

This holiday season I’d like to take you back in time to 2010… and the 18th century. Each winter when living in Raleigh, I liked to take a weekend trip to see something Christmasy on the east coast before heading home for the holidays. Ten years ago almost to the day, I planned a Sunday get away to see a rustic, foraged Christmas at Colonial Williamsburg in Virginia. In an age before the crafting of Pinterest and Instagram became more prevalent in our lives, it was so inspiring to see simple, everyday plant parts used in such clever ways to bring a bit of joy and delight to this darker season. And, I return to these photographs each year to see ideas and inspiration I got from my visit. So, enjoy the below photos that I took that dreary day walking the old-timey streets of this historic town.

As you’ll see in these photos, fruits played center stage in many winter arrangements. Here, pomegranates, lemons, and apples are set with dried artichokes and coniferous cones.

The acid green osage orange plays well here with pineapples and apples. Sumac seedheads, wax myrtle fruit, and catalpa pods are up top.

Here the halls are decked with apples and deciduous holly.

Some of the wreaths and designs were a bit less traditional. I loved this banner above the door.

Magnolia leaves were used in many wreaths for their evergreen nature, and I loved how they incorporated clam shells and dried yarrow heads to create a faux magnolia flower in this wreath.

Many decorations were primarily made from dried goods like the chaste tree branches and sunflowers here.

A bundle of wheat makes a striking door accessory.

Here dried plant parts make up the red, white, and blue.

The peels of dried oranges were used to add some zest to this arrangement.

And, here we see slightly dried oranges used as pendulous ornaments with pomegranates and acorns.

Even dried oak leaves were incorporated into some wreaths.

This wreath was my favorite of the day. Not only did I love the use of cotton to simulate smoke, but the color echo of door and wreath and the asymmetry of the cotton with the variegated holly was spot on.

In the south I worry about fruit having holes punctured in them for wreaths. This design solved that problem by wrapping the fruit with colorful fabric.

Occasionally, I saw doors with blue ribbons that were awarded for the most creative designs. To make the designs in the spirit of the place, there were rules like one could only use materials that colonists would have available to them back in the day. So, here you see a fish made out of gingerbread.

This design was another blue ribbon winner. A gingerbread queen bee watched over her hive and honey.

And, I was delighted to see a Star of David with adorning dreidels.

And, I can’t leave showing you photos of horticulture in Williamsburg without a picture of the vegetable garden and the clever techniques displayed for how early gardeners could have extended the harvest! Here you see cut branches, cloches, mulches, and paper frames used to protect early crops. The paper frames were the most interesting to me. From the gardener Wesley Greene, I learned that day they were made from cotton and coated in linseed oil. These designs date back to the 1770’s. So, if colonists can extend the season, so can we.

Feather Bluestem against a Golden Sunset

Driving to and from town I’ve admired a big patch of Andropogon ternarius in late season splendor right up the road.  It's pretty easy to spot once it comes into flower.  The inflorescences have this sheen to them, almost like long silver paintbrush bristles.  A month or so later, the bristles fray as the seed ripen, and the plant forms a pair of feather-like infructescences.  The seed heads glow a white blush no matter how the sun shines on them. Most people call this species split-beard bluestem, but I’m partial to the common name feather bluestem for its twin inflorescences that resemble bird plumage.

Before metamorphosing into the feathery seed heads, the flowers of Andropogon ternarius look like silvery paintbrush bristles.

I stopped the other evening as the sun approached the horizon to take some photographs of this colony of feather bluestem.  Just like the rest of the landscape, the grasses glowed warm in the waning light of a cool evening. 

Andropogon ternarius en masse. I wonder if the purpletop grass behind it to the right is a bit jealous just how good the feather bluestem looks?

The culm colors were variable, but some were a vibrant cinnabar.  I pondered if the coloration I saw was more an effect of genetics or the stresses of the site.  I could see drought or low phosphorus bringing out these red colors more. 

The cinnabar-colored culms warm the heart on a cool evening while photographing Andropogon ternarius

While the primary role of the hairs, technically trichomes, is to help the seeds disperse in a stiff breeze, I’m amazed at how well they capture light and diffuse it. From a distance they look like lines of white dots, a natural pointillism if you will.  However, up close when I stood behind the plants and squatted down to see the sun through them, I noticed an interesting phenomenon with how the waning light interacted with the seed hairs.  The light formed concentric circles around the sun as each bristle became a mini light reflector. 

The light orbits the sun in the seedheads of Andropogon ternarius

In my photographing the plants against the light, a Carolina Wren popped up to the barbed wire fence and sang its cheeseburger–cheeseburger-cheeseburger song.  It pranced a little bit, perhaps curious who was disturbing its niche, before flying off home. 

The bird of a feather bluestem. I wonder what this Carolina Wren thinks of Andropogon ternarius?

I'm so glad I stopped to enjoy the beauty of these feather bluestem late that Wednesday afternoon. Two days later roadside mowers came through and cut the whole patch to the ground.  It is sad the feather bluestem won't be there for me to enjoy it all winter as I drive to town.  But, in their clearing the roadsides, they just propagated more of the plant by dispersing those seed for me to enjoy in years to come.

I, too, will be propagating this plant via seed. You see, having lived here for four years, I was anticipating their autumn cutting, and I collected some seed that evening in the twilight. I’m just glad they waited long enough for me to enjoy this final show and let the seed ripen. And, soon I won't have to just enjoy the patch down the road.  I'll have my own feather bluestem here glistening in the setting sun for my enjoyment and the Carolina Wren’s. 

Thanksgiving Snowdrops

Thanksgiving makes me think of snowdrops because the weekend after the holiday my friends and I would travel to Hillsborough, NC to see one of the rare forms of Galanthus at Montrose, a historic garden tended by Nancy Godwin.  While most snowdrops typically start flowering later in winter, these autumn snowdrops (Galanthus elwesii var. monostictus) can be in full flower sometime around Thanksgiving, a full month or two earlier than other Galanthus. 

Closeup of autumn snowdrops. I love how the petals of the inner perianth have the green upside down heart on them.

My friends Alice, Keith, and Kim traveled with me on my last trek to see snowdrops while living in Raleigh in 2013.  The weather that Sunday afternoon was lovely.  Nancy described the mid-fifties with a sunny, bluebird sky as a “miracle,” and with it and good conditions over the past few weeks, the snowdrops were looking superb.  

Nancy stops our group briefly at Montrose to give us a teaser of the tour.

We were some of the earliest of the sixty or so visitors to descend on the garden for the snowdrop walk, and our prompt arrival ensured us Nancy as our head guide.

As we approach the back of the garden, excitement began to build as THOUSANDS of snowdrops come into view.

GASP!  It almost looks like a dusting of snow in places, doesn’t it?

While Galanthus can be appreciated while standing, the diminutive size of snowdrops beckons gardeners to humble themselves upon the earth to appreciate their beauty, much like we see Kim doing here with her camera.  

Nancy was keen to lead us along the path to highlight her favorite views, which finally crescendoed into us seeing the plants with the sunlight to our backs and the snowdrops in our front, a perfect angle for the light to play off the flowers well.  She tells us that in 1987 she acquired 12 bulbs from a local seed store for less than a dollar, and by happenstance they were this rare variety.  She started the mass planting seen above in November 2002 and has helped it enlarge via division.  She made the comment that she’s glad she bought the bulbs.  We are, too. 

The snowdrops don’t stop here. We are then lead through the woods where a large, long drift—perhaps a 1/10 of a mile long—has been planted, and along the path Nancy points out a few Cyclamen coum that have just started flowering.  However, most need not be in bloom to be attractive as the leaves on some cyclamen appear as if ornately arrayed shields of green, gray, and white.

The long drift pulls you into the woods to see just how far it goes.

Some of the diversity in Cyclamen foliage along the path through the woods.  The leaves look like little shields scattered upon the forest floor.

For me, snowdrops mark a turning point in the year, evidence that even though winter is here, spring approaches.  Many gardeners are fascinated by these winter bloomers to the point of obsession.  I’m not there yet, but I hold with Christopher Lloyd as he wrote in Garden Flowers, “We all of us need more snowdrops in our gardens”, and “[s]nowdrops are graceful, welcoming, sheer delight, and I fail to see how one could have too many of them.” If you’ve never seen them before, the pictures included here will certainly help.  When visuals are absent, I describe the plants as diminutive street lights, the white perianth dangling from six-inch scapes, much like a lantern might have hung from posts in days of old.

Galanthus flowers hang like lanterns on hooks. While they produce no foot candles, they certainly brighten winter.

The lantern comment brings to mind a story I once heard in a sermon.  Robert Louis Stevenson as a child was sickly.  One evening, the nurse came to check on him and found him sitting near the window watching the lamplighter.  The nurse hastened him to get back in bed, but he was mesmerized by the lamplighter who he said was “poking holes in the darkness.” For me that’s what snowdrops do.  They poke holes in the darkness of winter, and having some that bloom early like these autumn snowdrops and some that bloom late can make sure that all of winter is a little brighter in our gardens.

Winter Botanizing in East Texas

I joined Peter Loos and Dawn Stover on a recent botanizing trip in early January to look at some of some rare native flora in east Texas.  Tagging along with us were Jordan Cunningham, Dawn’s greenhouse assistant, and Cole Gandy, a horticulture graduate student.  

SEEDS OF A BOTTLE

Our first target for the day was Gentiana saponaria, the soapwort gentian.  While plentiful back east, it is very rare in Texas. Naturalist Matt Buckingham stated that there may only be five populations in Texas.

Gentiana saponaria habitat in east Texas.

While the plants bloomed back in November and December, our quest today was to ascertain the seed set on them.  We arrived at our site far down a logging road under gray skies on a warmish winter day.  Dawn and Peter had flagged plants back when they were in bloom, and now we could check pollination success.  

While many flowers had no seed, some did.  Gentiana saponaria is a bottle gentian, named because the tops are closed and require a pollinator like a bumblebee to force them open.  Dawn found a capsule split above a flower and pointed out to me how interesting the seed dispersal was.  We looked at some seeds closer up.  They were as fine as dust and resembled teardrops.  At the time, I thought it odd as to how the capsule got above the spent flower.   Once I got home I would discover that once pollinated the pedicle of the flower actually elongates so that the seed can find a new home.  We checked approximately 25 plants, but I’d say we only observed seed on about 7 of them. 

A hint of color left on this Gentiana saponaria

Once pollinated, the pedicel elongates to disperse the next generation. If you look closely at the base of the V, you can see the dusty, white seed.

Here’s a close up of a damaged seed pod. Notice how fine the seed are.

Peter Loos checks a Gentiana saponaria for seeds. Many grew on the sides of the creek.

Most of the plants that we looked at were either clinging to the edge of the stream or within 20 feet of it.  The stream likely acts as a refugium for this species, providing water and perhaps a fire break to prevent reproductive damage.  Peter commented to Cole that later in life he should come back and see if the gentians are still here.  We certainly hope so, but this species is likely a relic from when Texas was much cooler and wetter.  If the climate continues its warming and drying trend, gentians may one day be absent from Texas.  That is why these investigations into the reproductive success of Gentiana saponaria are important.  Dawn and Peter’s work is trying to prevent their demise and preserve the genetics of this southwestern population.

WITCHHAZEL HUNT

The second species, and one that I have wanted to see for some time, was Hamamelis ovalis, the big-leaf witchhazel.  I’m a witchhazel nut, and I wish so much that we could grow many of the hybrids in Texas.  But, alas they struggle in the deep south due to our lack of chilling hours.

The other reason I was excited to see this species is because it is fairly new to science.  In 2004, Steve Leonard found what would become Hamamelis ovalis in Mississippi. He noted even though it had similar red-to-yellow flowers and bloom time to Hamamelis vernalis that occurs in the Ozarks, it was about 600 miles further south.  And, while this witchhazel distribution overlapped with Hamamelis virginiana in the Mississippi locale, this species had larger leaves and tomentose (aka fuzzy) undersides to the leaf.  He published the name and description along with a great write up in Sida, Contributions to Botany in 2006. Then, in 2009 Wayne Webb found a population of these plants in Alabama, and since then it has been found in a total of five counties in Alabama.

Peter said that he had been shown this Hamamelis by Lynn Lowery in mid-1980 when these populations in east Texas were classified as disjunct occurrence of Hamamelis vernalis.  Later, Peter found additional sites like the ones we saw last May on our class outing, and it was sometime around 2010 after Hamamelis ovalis was named that he began to suspect that what occurred in Texas was actually Hamamelis ovalis all along. He and other native plant experts in the area have come to the same conclusion.  

Even though it may only occur in a handful of places in the southeast, this southern species deserves wider use. Hardiness further north doesn’t seem to be much of an issue. There are specimens in the Arnold Arboretum in Massachusetts (zone 6b).

Hamamelis ovalis begins flowering in the wilds of east Texas. Their strap-like (aka ligulate) petals unfurling reminds me of octopus tentacles.

We parked on a logging road, and clambered up the hillside of the right-of-way to find a dense thicket of trees.  Right inside was a wide10-foot-tall Hamamelis ovalis just starting to put on a show.  The flowers were smaller, just like the rest of its native cousins. However, they were colorful, and many individuals reminded me of the coloration you see on ‘Jelena’ or ‘Wisley Surpreme’.  Peter commented that we were early.  Last year when he visited, he could see the large tree through the brush from the other side of the road. 

I had read online another identifying feature is to tug on the new shoots around the base.  On Hamamelis ovalis, they will give some, and sure enough branches did rise up from the ground with a gentle heave.  My hands moved from a larger branch to a smaller pencil-thin whip and I noticed an abundance of pubescence.  As far as fragrance, it varied specimen to specimen.  Some you would catch that sweet witchhazel smell while others had little if any scent.  

As we explored the population, Peter pointed out a large colony of Texas leaf cutter ants and commented that they had been there as long as he has been visiting this site.  The space the mounds occupied could have easily fit into two or three parking spots.  He joked, “This time of year, yaupon holly is about all you’ll see around the holes.  They’re caffeine addicts!”  

A Texas leaf cutter ant mound. Notice the abandoned shreds of Ilex vomitoria.

A minute or two later as I was photographing a witchhazel I noticed one of the ligulate petals moving.  A leaf cutter ant was hauling it away!!!  I gave a little squeal at seeing this little marvel of nature. Seems we humans are not the only creatures that enjoys the blooms.  

A Texas leaf cutter ant carries a witchhazel petal.

Having seen the diversity at this site, we got back in our cars, and drove down the road a bit to a second Hamamelis ovalis site at a local trail.  We walked about half a mile to a see a second population, passing emerging Trillium and a forest that more closely resembled the east coast than Texas.  

Early Trillium foliage rises from the leaf litter.

We reached a spot in the trail where more light came through the bare canopy.  At first, all we could find was small Hamamelis saplings, but before we left I was spotting small trees 12-to-15 feet tall with their blooms high above.  Peter said that many of the runts were likely small due to dense shade from the canopy, but a storm a few years ago removed some branches and opened it up for more light to reach the forest floor. 

One of the taller big-leaf witchhazels. You can see the blooms against the darker colored tree trunks.

While we noticed more interesting color variants (even a yellow flowering one!), it was here that I really started to see some clonal nature to this species.  Two specimens a few feet apart would have the same color pattern, or you could see at another colony where two seemed to grow out from the same spot yet be a few feet apart.  Another gentle yank on some showed me the plants had layered on the forest floor.  

This clone faded from red to orange to yellow in the petal.

A more orange colored form.

We even found a yellow flowering big-leaf witchhazel!

At this second location, I also saw Hamamelis ovalis exhibiting a common characteristic to witchhazels, marcescent foliage. It varied from clump to clump as far as how many leaves were retained, but in general most of them were deciduous.

We headed back to the cars from a day full of botanizing and learning more about the flora of Texas.  Even in the dead of winter there are plants to be enjoyed, and with a better understanding of soapwort gentian and big-leaf witchhazel, I hope these jewels of the winter landscape can be preserved and continue to shine for many years to come.

One final glimpse of big-leaf witchhazel in flower. What rich color for a gray day!