Douglas A. Spilker, Ph.D., is a consulting ornamental plant pathologist and entomologist, garden writer and lecturer. Dr. Doug can be reached at

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Gardening Questions You Never Really Thought to Ask
by Douglas A. Spilker, Ph.D.       #Misc   #Pests   #Uncategorized   #Vines

Oaks typically alternate years of heavy acorn production, just like fruit trees.

Often when pulling weeds or mowing the grass, my mind drifts to some of the challenges in the world. I don’t mean solving world hunger or anything, but just considering some of those gardening questions not discussed on radio shows. This happens in a “stream of consciousness” where one thought or question runs into another and another and so on.

As I mow, I often wish that I could quit mowing my grass and let the seedheads develop. Would this fill in the bare spots? I know my neighbors wouldn’t like it, but I also know there are cultural reasons that this doesn’t work. Most perennial grasses, like Kentucky bluegrass and fescues, are hybrids; they commonly do not produce viable seeds. Better keep mowing and avoid nasty letters from the homeowners’ association.

Nutsedge tubers (nutlets) can persist for years in the soil waiting to appear in lawn bare spots.

Mowing has its own hazards. Last year my oak tree was raining acorns, and mowing was like skating on marbles. It was driving me nuts — why were there so many this year? Oaks typically alternate heavy acorn production years. It takes a lot of energy to produce the fruit (nuts), and therefore less goes into making the flower buds for the next season. I think “off” years can also occur when a late spring frost blights the flowers, reducing nut development.

Although they don’t produce real nuts, I don’t recall having any nutsedge (also known as nutgrass) in my yard last year, but there it is. Where did it come from? It may have been hiding there for a while. It is not uncommon for their persistent tubers (nutlets) to be trucked in with the top soil used during yard grading. Watch also for infested soil with nursery stock that might introduce nutsedge into landscape beds.

Although nutsedge is a challenge in lawns, the common yellow wood sorrel (Oxalis stricta), known by many names including sour clover (taste it and see why), is nearly impossible to eradicate in flowerbeds. Does it spread by spontaneous generation? It is important to remove plants before seedpods develop, because when ripe, they explode at the slightest touch, launching seeds as far as 10 feet. I am convinced this is how it spreads.

Speaking of explosions, why do earthworm masses try to commit suicide after a heavy rain? There are several theories as to why earthworms surface when it rains. I always assumed it was to keep from drowning in waterlogged soils, but earthworms thrive in moist environments. Some say it is easier for them to migrate to another location or to find mates. However, I like the theory that they scatter because raindrops cause soil vibrations that scare them into thinking a mole is coming. (Sounds more exciting to me.)

Murphy’s Law?

I’m convinced that Murphy was a gardener. Take for instance my iris bed. I started with a nice assortment of bearded irises. Over the years, I lost a few for various reasons, but some always came back. Finally one year, one color took over — guess which one? The ugly purple-brown ones. And don’t even mention my favorite yellow pear tomatoes. I searched all over town looking for transplants, and found the very last one in a local nursery. I was so happy to get it planted in time for the next rain. Not more than a week later a big storm came through. The only damage in the whole garden was the broken stem of my sole pear tomato. Murphy did it again!

Earthworms aren’t the only soil-borne critters we seldom see. Why don’t we see cicadas more often? Cicadas live most of their lives underground, within 2 feet of the surface, feeding on tree roots. After 13 to 17 years, cicada nymphs emerge synchronously and in tremendous numbers. Within two months of their emergence, eggs have been laid and the cicadas have returned underground chewing on roots for another 13 to 17 years.

Squirrels don’t chew on roots, but they can chew through anything that is not metal, but that doesn’t mean they don’t chew on metal. But why do they have to gnaw on our new patio furniture? The front teeth of squirrels, just like beavers, continue growing throughout their lives. To keep them trimmed, they chew on “stuff.” If they run out of nuts, they chew on your house, your property or anything else to keep their teeth trimmed.


Squirrels might not eat the metal, but they can do plenty of damage to patio furniture. • Vines (like this Mandevilla sp.) twine according to their genetics, not due to the hemisphere they live in. • Rabbits are not my friends.

If you don’t trim vines, they undoubtedly will twine around any support. What causes vines to wrap one way or the other? Most vines twine counter-clockwise, though about 10 percent go clockwise. Some do it both ways. Unlike swirling water down the sink, the twining direction of vines is not dependent on whether the plant grows north or south of the equator. Simply, twining direction is genetic; some species go one way, while others go the other way.

There are many mysteries in the gardening universe, some which will never be solved like: “Why do rabbits go for vegetable seedlings when they must cross yards of lush green grass to get there,” and, “Do cutworms have a mean streak by felling a seedling with one bite then moving on to the next?” I’m sure you have many of your own gardening mysteries that also keep your mind flowing like a stream (of consciousness).


A version of this article appeared in a July/August 2016 print edition of State-by-State Gardening.
Photography courtesy of Douglas A. Spilker, Ph.D.


Posted: 07/03/18   RSS | Print


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