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No gardener has the right to use a poison that could harm their neighbors or the environment

  • Author: Jeff Lowenfels
    | Alaska gardening
  • Updated: May 6
  • Published May 6

The other day a reader wrote, utterly condemning me for suggesting we use the bacteria Bt to kill delphinium defoliators that are emerging in the crowns of delphinium plants and destroying leaves. How dare I suggest we poison a pollinator when we are in dire need of them. She made it very clear, in no uncertain terms, that she won’t be reading my columns ever again.

I hope she will reconsider. But I must say, I am glad she notified me, because she is absolutely right in one way, though wrong in another. First, let’s deal with the the delphinium defoliator.

Yes, it is a caterpillar, but it morphs into a moth and not a butterfly. The moth is known as the “leaf-tier moth,” aka Polychrysia esmeralda, and while some moths are pollinators, the delphinium is this critter’s food plant, not all the other plants in your gardens, unless you are growing larkspur. While the delphinium is necessary for the life of the moth — a caterpillar eats a leaf a day — the moth is not necessary for the delphinium to survive, as other insects pollinate it as well. So we are not affecting any pollination of other plants when we take out delphinium defoliators.

If anyone is still concerned and wants to keep populations alive — I did see one report that they will pollinate fireweed sometimes — leave one or two plants untreated. And if you are worried about using bacteria as a pesticide, search and hand-pick every morning.

Still, the note caused me great pause. I stepped back and reoriented a bit. As gardeners, we always need to keep reminding ourselves to continually examine and adjust gardening practices to ensure we do no harm to ourselves, others and the environment. (Oh, oh. Lowenfels rant coming).

You really must have a clear reason to act if you want to take out an organism that gets in the way of your gardening. Of course you should use the proper mode to do so and make sure you are extremely selective so as to hit only the target, but you need to look at all the factors first: Is the organism native to our area? Who relies on that organism for their existence? Should you be planting the host in the first instance?

Gardeners are not trained to think this way. We assume if it is sold in a nursery, we can safely grow it. A great example, in my opinion, of the right way to go is not spraying for spruce bark beetle. We sacrifice majestic trees because there isn’t an on-target way of eradicating only the beetles and not the fish, birds, bees and yes, moths in the area. Is my delphinium’s situation that different? In this instance, the Bt saves the plant and doesn’t appear to harm anything but the moths.

To continue the thread of thought stimulated by the email, there most certainly is a great deal to be said for simply not planting delphiniums in the first instance if they are going to require a human to step in and take out a pest they bring with them. Yes, delphiniums perform more spectacularly here in Alaska than any other place I have seen them, but delphinium are not a native plant here. Perhaps only our botanical gardens should be growing them and they are not a suitable Alaska yard plant.

This is the beginning of the season. No gardener has the right to use a poison that is going to harm the environment, neighbors, and in the case of spraying, strangers far, far away. And no garden writer has the right to encourage you to do so. We all have to be mindful of what we are doing in our yards and gardens. They are not our kingdoms to do with what we want. It isn’t the 1950s and we have to stop thinking like it is. My ex-reader is correct in that.

So, we are in the throes of getting set up for the summer. We should be buying seed, starting plants, visiting nurseries and getting starts. We should also make a concerted effort not to buy fertilizers and poisons or even plants that need them.

Jeff’s Alaska garden calendar

Visit nurseries: Get plants, potatoes, mycorrhizal fungi, stakes and anything else that is on the list.

Seeds to plant outdoors in the soil: Peas, nasturtiums, chard, onion sets

Sweep: If you do nothing else, just sweep up a bit. It will look like you did some yardening.

Alaska Botanical Garden: What are you waiting for: join. Plant sales are starting. Sign up your junior gardeners for camps; sign yourself up for classes. Visit. Enjoy. It is one fantastic place.