Update on Monarchs

Submitted 3 months ago
Created by
Henry Homeyer

I recently reported that I had been seeing monarch butterflies nearly every day, and attributed it to my planting of various milkweeds. These plants, including swamp milkweed (Asclepias incarnata) and whorled milkweed (Asclepias verticillata) provide them with pollen and nectar from their flowers, and the leaves can be eaten by their caterpillars.

Swamp milkweed with a monarch feeding

Monarch butterflies and especially caterpillars, it is believed, develop a nasty taste to birds because of their habit of eating milkweed plants. Milkweeds contain several toxic glucosides which the caterpillars concentrate – making them relatively inedible to predators.

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I have been getting e-mail from readers who report that they have been seeing not only the butterflies this year, but also caterpillars. In each case, the gardener reported that she was allowing common milkweed (Asclepias syrica) to grow and spread in her gardens.

I do not have any common milkweed. I planted seeds last year, they grew to be small plants, but did not winter over. I may be the only gardener in New Hampshire planting weeds that didn’t survive! But here’s the thing: I don’t, as yet, have any caterpillars on my other milkweeds. This week I was inspecting some roadside milkweeds, and saw a monarch caterpillar on a common milkweed plant.

Monarch caterpillar feeding on common milkweed. Photo credit :Jean Hines, Plainfield, NH

So I am going to get some common milkweed plants, and start a patch of them. I have learned since last year that common milkweed can spread by root, and be quite a pest if you introduce it to your garden beds. So I will plant it off to the side in an area where it can spread and grow – without being a pest.

Common milkweed has a tap root, so I will find the smallest plants I can find, and dig them. If you are seeing monarch caterpillars, please let me know. Either post something in the comments section below, or e-mail me at henry.homeyer@comcast.net.

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