Fielding Questions: Iris blooming in fall, houseplant granules, grass under raised bed

Q: As I was out in garden on Saturday, October 7th, my eye caught a glimpse of deep purple, and I was surprised by a beautiful iris with 6 buds! I brought several inside, and they’re making a lovely show of ruffles in deep purple. – Susan Clambey

A: Thanks, Susan, for writing and sharing the nice surprise about the October-blooming iris. What a beautiful flower!

There are a few iris cultivars that are termed "rebloomers" that will flower during the usual iris blooming time in June and occasionally again in fall. The key word is "occasionally," as they don't rebloom reliably every year, but apparently when conditions are just right to trigger the second bloom.

I'm sure the trigger for these rebloomers is some combination of temperature, moisture, fertility, age, and length of growing season.

One of the most common reblooming iris cultivars is the white 'Immortality,' which flowered for us just recently also. It didn't produce the mass of flower stalks that it did in June, but it did yield one stalk with two nice flowers, which was a welcome treat. October does seem a little late for the rebloomers, with September being the more likely month.

Thanks again, Susan. As a sidenote to readers, Susan’s husband, Gary Clambey, is a North Dakota State University professor emeritus of biological sciences. Dr. Clambey taught several of the key classes I took in college over 45 years ago. Where has the time gone!

Q: I’m a huge fan of overwintering plants indoors, and have almost 200 houseplants already. In a previous article, you mentioned granules. What were you referring to? I was on Amazon and could use help finding what you recommend. – Claudia H.

A: Wow! It sounds like you have an indoor botanical garden! You, like many of us, treasure our indoor plants, but insect control is a continual challenge, and that’s what I was addressing in a recent column when I mentioned granules.

The granules I recommended were systemic insecticide granules which are an option for controlling insects on potted plants. Systemic insecticides are applied to the soil, taken up by the root system, and spread internally through the plant’s sap system. As insects like aphids and spider mites suck plant sap, they are killed.

I don’t endorse commercial products or brands, but the most commonly found systemic products in garden centers are Bonide Systemic Houseplant Insect Control and Hi-Yield Systemic Insect Granules. Always follow label instructions.

Q: Do I have to kill the grass before I install a raised garden bed on the ground? – Carol H.

A: Good news. No, you don’t have to kill or remove the grass before building a raised garden on an area that is currently lawn.

Grass doesn’t need to be removed first, because it will die from smothering and quickly decompose into compost below the raised garden. If the raised bed is deep enough, the depth of soil alone will provide smothering. If a raised garden isn’t deep enough, grass could resurface.

To be safe, no matter what the depth of the raised garden, it’s better to put an underlayment over the grass in the bottom of the raised bed. Water-permeable landscape fabric can be used with good results. I frequently use cardboard, which after accomplishing the smothering, breaks down into organic material.

If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at donald.kinzler@ndsu.edu . Questions with broad appeal may be published, so please include your name, city and state for appropriate advice.