Common Milkweed ~ Asclepias syriaca

Recently a friend inquired that if I had to choose one native New England plant to grow to attract butterflies to the garden, which would it be, and why. It was a challenging question because butterflies are typically drawn to the garden planted with a rich and varied, yet very specific, combination of species. A successful Lepidoptera habitat is comprised of many elements all working in tandem. Sunny and protected areas in which to warm their wings, trees and shrubs that provide shelter, and a host of nectar plants for the adults, as well as specific caterpillar food plants, create the successful Lepidoptera garden.

Perhaps if I had to choose a favorite butterfly and therefore a favorite plant to grow to drawthis butterfly to my garden it would have to be common milkweed (Asclepias syriaca), which is both a larval host plant and nectar plant for the elegant Monarch butterfly. People often speak unkindly about common milkweed, rather I think it deserves applause for it is plant without rue and thrives wherever found—in the cracks of city sidewalks and along country roadsides, highly-trafficked soccer fields, and in the most neglected of neighborhoods. Whether in the garden, along the shoreline, or local meadow, it is on the foliage of common milkweed that we find the vast majority of Monarch eggs and caterpillars. Noteworthy also is that we observe many different species of butterflies and skippers nectaring at common milkweed—sulphurs, swallowtails, and fritillaries, to name but a few. In our garden we grow common milkweed alongside marsh milkweed (Asclepias incarnata); marsh milkweed blooms slightly earlier than common milkweed as it is sited in a sunnier locale. Both species attract a wide variety of winged pollinators. Male and female Monarchs nectar from the blossoms, while the males simultaneously patrol for females. The females utilize the foliage of both species to oviposit their eggs. Typically we observe females freely flitting alternatively between our common and marsh milkweed, depositing their eggs on the choicest leaves and buds, while pausing frequently to nectar.

Monarch Butterfly Egg on Common Milkweed Leaf

The milky sap that flows through milkweed veins lends the genus its common name. Monarch butterflies and their caterpillars have evolved to withstand the toxic milk, but not the predatory bird that attempts to eat one. The adult Monarch’s unique wing pattern and caterpillar’s striped suit warn of its dreadful taste and lethal toxins. A bird that is tempted becomes sick and may even die, and if it survives, remembers never again to try to eat a Monarch. “The larvae sequester cardiac glycosides from the milkweed leaves that they consume. Concentrations of these heart toxins in their bodies may be several times higher than those occurring in milkweed leaves. The glycosides consumed by the caterpillars are carried forward both into the chrysalis and adult stages, affording them protection as well.” (Caterpillars of North America David L. Wagner).

Common milkweed is highly adaptable and grows in nearly any soil. The size of the developing colonies and individual plants reflect the conditions in which it is grown.  Planted in a rich, moist soil, protected from the wind and where it receives some light shade, it will grow six to seven feet.  I use it extensively in my butterfly garden designs, planting in rich, average, and dry conditions, and find it especially appealing and useful for shoreline gardens. In sandy soil, sand dunes, and meadows, where it is exposed to wind and/or salt spray, common milkweed is equally as vigorous, but of a much shorter stature, typically obtaining the height of two to three feet.

A. syriaca thrives in full sun to light shade. In a moist, protected area, plant in the back of the border. In a more exposed site, plant in the mid-ground. Because of its ability to spread readily and rapidly, use in an informal, natural setting as opposed to planting in formal  beds.

Common milkweed is highly fragrant and is the most richly scented of the species of milkweeds found in Massachusetts (A. incarnata, A. syriaca, A. quadrifolia,  A. tuberosa, A. amplexicaulis, A. exaltata, A. pupurascens, and A. verticillata), with a complex wild flower honey fragrance. I have heard it described as similar to the scent of lilacs, but find lilacs have a much sweeter fragrance than common milkweed. Fragrance is highly mutable and subjective.

One- to two-year-old plants are easier to transplant than established plants. Common milkweed takes approximately three years to flower from seed. The method in which I have had the greatest success in propagating Asclepias syriaca, best attempted in early summer, is to dig up a rhizome, found at the base of a plant with newly emerging shoots. The rhizome would ideally be obtained from a friend’s garden. If collected in the wild, be sure to dig from an area where there are many shoots present. You need a fairly large chunk, at least a half-foot, with both roots and new shoots present. Replant the rhizome at the same depth. Water throughout the summer. Towards the end of the growing season you will be rewarded with newly emerging shoots. Common milkweed self-seeds readily, but spreads primarily (and rambunctiously) by its rhizomatic root structure.

Milkweed in general, and in particular, common milkweed, attracts a host of pollinators—bees, wasps, butterflies, and purportedly hummingbirds. I have yet to see the Ruby-throated hummingbird nectar from common milkweed, but it may also be the case that they are attracted to the plant for the multitude of tiny insect populations frequenting the flowers (over ninety percent of a Ruby-throated hummingbird’s diet is comprised of insects). We typically findMonarch eggs and caterpillars on milkweed plants during the months of July and August.

Buddleia davidii ’Nanho Blue,’ with blue-violet racemes, melds beautifully with the muted lavender rose florets of the softly drooping flower heads of common milkweed. The brilliant white of native Phlox davidii and vivid purple-pink of Liatris ligulistylus attractively offsets both. All are famously attractive to Monarchs (and myriad other species of Lepidoptera) and will provide a long season of nectar-rich blossoms and Monarch caterpillar food.

Monarch Butterflies Mating on Common Milkweed Leaves

A note about the video: Monarch butterflies deposit eggs on common milkweed (Asclepias syriaca) and marsh milkweed (Asclepias incarnata) in eastern Massachusetts. The chrysalis in this video was attached to a marsh milkweed stem. For a wealth of information on butterfly gardening, read Oh Garden of Fresh Possibilities!