Impatiens problem forces rethinking of shade garden

Last July, I started getting inquiries about why impatiens (Impatiens walleriana) were dying. At that time, mine were doing just fine and I figured it was a local problem caused by too much water or because of the heat wave we had at the end of June, which would have stressed the plants.

I did not think much about the problem until all of my impatiens started dying, too. I had them planted in about six different locations, and I knew all of them should not be biting the dust at once. Then I learned from a cousin in North Carolina that downy mildew was affecting the entire Southeast.

Downy mildew on impatiens is a relatively new problem in our area, and it cannot be controlled effectively in the landscape. The downy mildew pathogen is Plasmopara obducens, and it infects bedding impatiens, both single and double. It is spread by wind currents, water splash or the movement of infected plants. I am told that fungicides are not always 100 percent effective at eliminating the disease and besides, if you did try using fungicides, you would have to spray weekly to keep the disease under control.

I have planted wax begonias in places where there is some shade but not deep shade like some of the places I had previously planted impatiens. These begonias do nicely in part shade or in full sun. Now I am going to see how they will grow in less sunlight than usual. The green-leaved varieties do better in the shade, and the bronze foliage begonias do better in the sun.

Begonias have always performed beautifully if they have some moisture and well-drained humus-rich soil. We will see how they do in shadier places where I used to grow impatiens.

I have visited several garden centers to see what would be a good substitute for the next couple of years. Here are a few recommendations that you might want to consider planting in those areas where you have previously planted impatiens.

Jackie Tucker, a most knowledgeable and friendly employee at Carolina Garden World, said torenia is a shade-loving plant that he is recommending to customers. It comes in many colors, and Jackie says they carry blue, white and purple. The common name of torenia is wishbone flower. It has an unusual upturned flower that looks similar to a snapdragon and has a wishbone shape in the “throat.”

I knew torenia but only thought it came in purple. However, today there are several series of torenia on the market featuring new colors. This plant looks great in the landscape as well as in a hanging basket or in a pot where it spills over the side of the container.

Jackie is also recommending Lobelia erinus, which comes in white and blue. I am relatively familiar with the blue form but had never seen the white lobelia before. The white variety is a spreader, growing 6 inches tall and spreading to about 12 inches wide, reminding me of bacopa. The blue lobelia has a clumping formation and is a beautiful iridescent blue.

You can also consider brunnera, hosta, heuchera and caladium for the shady areas of the garden. They are all readily available around town.

New Guinea impatiens (Impatiens hawker) have a high resistance to downy mildew. You are safe in planting this variety. They are a good plant, but they require full sun.

This situation gives you a chance to be creative and learn about new plants that you might not have planted in your shade garden before. Good luck, and happy gardening.

Reach Betty Montgomery at bmontgomery40@gmail.com or 585-9213.