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Common Milkweed (Asclepias syriaca)

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Summary

A sun-loving perennial native to a wide range in North America, best known for being a preferred host of the Monarch butterfly.

Range - Expand

This map is based on the FHWA's ERA. This data overestimates native ranges, especially around the edges, as this post explains. We have not yet reviewed this map.

USDA Plants Profile for Asclepias syriaca

Illinois Wildflowers Page for Asclepias syriaca

Habitat

Fairly general in its habitat preferences, and tolerates a range of conditions, but prefers full sun. Tolerates both sandy and clay soils, including compacted soils.

Common along roadsides and railroads, field margins, in abandoned fields, vacant lots, industrial sites, and other open, disturbed sites. Among less disturbed wild habitats, found on prairies, shale barrens, and sand dunes of freshwater lakes.

This species has historically benefitted from the influence of humans, but in recent years, the pressure for higher yields in agriculture, and management-intensive landscaping in developed areas, has reduced or eliminated many of the field margins and small, disturbed habitats where this plant thrives.

Life Cycle

Common milkweed is a perennial that often forms large vegetative colonies from underground rhizomes.

New plants sprout from seed and quickly establish a taproot. The first year, the plant usually has only a single stem, often does not reach full size, and often does not bloom. With each subsequent year, on favorable sites, the plant spreads horizontally and more stems form. Rhizomes are often several inches underground and can grow several feet from the parent plant.

Seeds are wind-dispersed, and require a period of cold, wet conditions before they will germinate in the spring.

Stems of established plants often emerge later in spring than numerous other plants.

In the absence of disturbance, common milkweed will often be replaced and out-competed by other vegetation after a few years. Disturbance that removes the competition, such as mowing to the ground early in the season before stems emerge, often favors this plant, especially when the mowing is timed late enough to harm plants that have already invested in significant growth.

Faunal Associations

Best known as one of the preferred hosts of the larvae of the monarch butterfly (Danaus plexippus), but also supports a diversity of other insects. The flowers attract a range of pollinators including bees, wasps, skippers, butterflies, and moths.

Uses

Widely planted as a landscaping plant, especially in wildflower and native plant gardens, where it is often valued specifically for hosting monarch butterflies.

Numerous other Asclepias species co-occur in most of this species' range; nearly all of them are native in North America, but one species, Asclepias curassavica, was introduced from the tropics.

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