The columbine (Aquilegia spp.) is a highly attractive perennial and very popular as well. With its exotic-looking flowers, usually bicolored (the color range includes red, pink, yellow, white and violet) and often with long spurs that extend towards the sky, its beauty is hard to beat. In addition, the spurs are filled with nectar and attract hummingbirds and butterflies. Even its curiously lobed foliage, like the leaves of a ginkgo or a maidenhair fern, and carried on very thin petioles, is just charming. But columbines have discouraged many gardeners over the years.
Their flaw? Mangled foliage!
Columbines are subject to not one, but two leaf-eating insects … and they come back year after year. Thus, either its leaves become covered with white tunnels or blotches (work of the leafminers Phytomyza aquilegivora, P. aquilegiana or P. columbinae, depending on where you live) or they disappear entirely, leaving a small forest of bare petioles, the leaf blade having been entirely devoured by the small caterpillar-like larva of the columbine sawfly (Pristiphora rufipes, formerlyPristiphora aquilegiae), the adult fly of which is rarely seen.
One or the other shows up every year, sort of dividing up the task. It’s as if the insects were saying, “It’s your turn this time. I’ll do the job next year.”
Learn to Ignore What You Can’t Change
The secret to growing columbines without becoming totally stressed out, at least from the point of view of a laidback gardener, is to learn to just let things happen.
In nature, columbines grow perfectly well despite the annual attacks of these two predators. True enough, the leafminer may trace whitish tunnels inside the leaf, but that doesn’t prevent the leaf from photosynthesizing and therefore flourishing. In fact, some photographers even find serpentine tunnels very photogenic!
And when the sawfly devours all the foliage leaving only stubs, the plant quickly produces a new set of leaves. Since the sawfly produces only one generation per year in most areas, the new leaves remain untouched and thus the problem is solved.
Wow! That was easy!
If You Feel the Need to Treat
OK, so you’re one of those gardeners who just has to react. (I personally think you should just take a Xanax, but that’s me!) If so, you’ll probably be dismayed to learn that there really are no good insecticides you can use to control columbine leafminer. Indeed, the tiny larvae (so small, all you’ll ever see are the tunnels they trace) live inside the leaf: most widely available insecticides act by contact and so won’t reach them. Yes, there are systemic pesticides, ones that are absorbed by the leaves and therefore can reach insects others can’t, but most were banished ages ago because of their extreme toxicity. Certainly, they are no longer being sold over the counter in most countries.
What then are you supposed to do with an insect that lives inside the leaf and not outside? The only logical solution is to cut off and destroy the affected leaves. This involves not only a fair amount of precision pruning, but your plant ends up looking like sawflies hit it, so is this really better than doing nothing?
As for the sawfly, whose larvae (rather stupidly, don’t you think?) live on the outside of the leaf, where you can get at them, there are several biological insecticides*, including insecticidal soap and neem, you can spray on to control them, or you can hand pick them and toss them, wiggling and squirming, into a can of soapy water. (Revenge is sweet!) But for that to work, you have to see them in time. Unfortunately, sawfly larvae are usually both numerous and very hungry: they can completely defoliate the plant in as little as 48 hours. That doesn’t give you much time to react!
*Note that the popular biological insecticide BTK will not work on sawfly larvae. It’s specific to caterpillars (larvae of moths and butterflies). Although the sawfly larvae may look like caterpillars and in fact are often called false caterpillars, they aren’t caterpillars but instead fly larvae and BTK will have no effect on them.
You Decide, But…
Despite foliage that comes and goes in the middle of the growing season, the columbine remains a very interesting perennial that easily adapts to most garden situations. It grows readily in both sun and partial shade and in most soils that aren’t overly dry. It’s also very hardy: most varieties will grow in zone 3 or even 2, depending on the parent species, and up to zone 8 in mild climates. Columbines also have quite a long flowering season, often over a month in late spring and early summer. True enough, individual columbine plants don’t live very long (three or four years is the norm), but they self-sow modestly but assuredly, and thus come back to beautify your flower beds for decades.
I say, “Hurray for columbines! Your zits don’t bother me at all!” Can you do the same?
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