Sometimes, lilacs can bloom twice in the same year
"Fielding Questions" columnist Don Kinzler also offers advice to readers about dealing with box elder bugs and late-season rhubarb care.
Q: In my 65 years I have never seen lilacs bloom twice. When I looked out the window this morning, I thought I saw pink blooms. I ran outside, and sure enough the lilacs were blooming in September. We have a row of about 30 at our home north of Fargo. Have you ever seen this before? — Kim K.
A: I am forever amazed by nature’s intricacies and how temperature, moisture, daylength and countless environmental combinations affect trees, shrubs, lawns, vegetables and flowers in various ways. Your reblooming lilacs are a great example of how nature triggers flowering.
Like you, I’ve observed lilacs blooming in September. The phenomenon of lilacs flowering both in spring and again in late summer or fall was apparently first noted in the early 1900s, mainly with lilac species or hybrids slightly different from the common old-fashioned lilacs.
Since then, plant breeders have dabbled with developing lilacs with the habit of repeating their bloom. Early attempts yielded varieties that only occasionally flowered a second time. Then in 2009, the cultivar named Bloomerang was developed, which bloomed more consistently both in spring and again in late summer. The variety has since become a hit in the garden center trade, and I planted one about four years ago.
Bloomerang lilac matures at about 5 feet high and 6 feet wide. The late summer flowers are not as large and plentiful as the spring crop, but they’re beautiful nonetheless.
Q: I am being inundated with box elder bugs. What is the best way to get rid of them? — Kaye P.
A: Box elder bugs are easily recognized by their black color and reddish-orange markings on their wings. They spend their summer sipping the sap of box elder and silver maple trees. Box elder bugs don’t damage the trees, and they usually go unnoticed until fall, when they start searching for heat and can be found sunning themselves on the south- and west-facing sides of buildings.
Box elder bugs are fairly harmless, but they can still be a nuisance. A recipe recommended by North Dakota State University that’s quite effective and safe to use on house siding is a homemade mixture of 5 tablespoons of dishwashing detergent added to 1 gallon of water. When sprayed on the insects, it kills on contact, but has no residual effect, so needs to be reapplied if the bugs congregate once more. Longer-lasting insecticides containing the active ingredient permethrin can also be used.
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Q: I stopped harvesting my rhubarb in late July, as recommended. Now the stalks look amazing. Do I pull and throw those before winter or do I leave them until they freeze and then toss or do I leave the stalks until spring? I’ve researched but can’t find a clear answer. — Jackie T.
A: Rhubarb stalks and leaves from midsummer onward are building energy back into the plant, so it’s a good sign your plants are looking good. Now, as the growing season winds down, if frost is forecast in the upcoming days, we can harvest some of the stalks for fresh use or processing. Rhubarb stalks should not be consumed after a frost that visibly damages leaves and stalks, because toxic compounds can translocate to stalks.
Whether or not you harvest some of the stalks for use, all rhubarb stalks should be gently pulled before winter after hard frost blackens the leaves and wilts the stalks. Let them dry down a little for easier removal, and then pull in late October or early November. Dead stalks are best removed for disease prevention. Leaf-spotting and stalk-spotting diseases can spend the winter on old plant refuse, so removal and disposal off-site can reduce future disease.
If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at firstname.lastname@example.org. Questions with broad appeal may be published, so please include your name, city and state for appropriate advice.