Milkweed Season

Milkweed has been getting a lot of press over the last few years regarding its vital role in Monarch butterfly reproduction. The destruction of milkweed plants, regarded as weeds, has a negative impact on Monarch populations. Over the years, I have tried growing a few cultivated varieties of milkweed (Asclepias spp) in my garden, but none have done as well as the native variety, Asclepias syriaca. It introduced itself to the garden and has settled in a few small stands which I leave to do their thing. The plants have just finished flowering and are now beginning to produce their pods of bewhiskered seeds, adored by children of all ages.

Yesterday I checked the leaves of some of the plants for Monarch caterpillars and was pleased to discover a couple of little munchers. You can watch for leaves with holes or ragged edges and gently turn them over. Monarchs tend to lay their eggs singly and each caterpillar had a leaf to itself.

But the Monarch babies didn’t have the milkweed all to themselves. I also found a cluster of tiny Milkweed Tussock Moth caterpillars voraciously skeletonizing the top leaves of their plant with gusto! it’s a wild world out there.

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On Milkweed

Common Milkweed (Asclepias syriaca) is one of a couple of types of milkweed found here. It features broad leaves on a sturdy stalk and around mid-summer, produces light pink flowers held in globe-like clusters. Each small flower features 5 hooded petals above with 5 sepals below. Milkweed takes its name from the white sap that is exuded if its stem is broken. Interestingly, the genus name syriaca means ‘of Syria’, because the plant grows well there, but it is actually a native of North America and was carried across the ocean by early explorers. Milkweed produces networks of runners about 15 cm underground, and each year a plant sends up new shoots from these rhizomes.

Milkweeds produce a lot of nectar and are popular with insects. Bees are the main pollinators. They feed on the nectar and carry away milkweed pollen on the sacs on their legs. The milky sap of the milkweed contains a glycoside which is poisonous to many animals. Several insects including milkweed beetles and monarch butterfly caterpillars, feed on the leaves and acquire protection from predators by retaining these poisons.

Milkweed is most readily identified in the autumn, when its large seedpods open and release their beautiful downy crop of parachuted seeds, which can often be seen floating on the wind. When I was a youngster, we used to call these floating bits of fluff Santa Clauses.

Swamp Milkweed (Asclepias incarnata) prefers moist ground and can be found growing along rivers and around ponds. It’s leaves are more lance-like than those of Common Milkweed, and the flowers are a much brighter pink. Like other members of the family, Swamp Milkweed produces a milky sap. Its long seedpods are are held in a more upright posture than those of Common Milkweed, but the fluffy seed parachutes are similar.

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