Sullivant’s Milkweed

Asclepias sullivantii

Description & Overview

Sullivant’s Milkweed is a threatened species naturally found in the wet prairies of Wisconsin. The flowers have deep purple petals and the centers are a delicate shade of pink. Flowers are arranged in clusters of up to 20 individuals and bloom for the whole summer. Smooth green seed pods release wind-pollinated seeds in the fall.

You may also know this plant as Prairie Milkweed or Smooth Milkweed.

Core Characteristics

Mature Height: 24-36 inches
Mature Spread: 12-24 inches
Growth Rate: Perennial
Growth Form: Upright, naturalizes, spreading
Light Requirements: Full Sun
Site Requirements: Average, moist to dry soil
Flower: Tiny (1/2-3/4”), purple-pink, fragrant, 1-3 clusters (umbels) per plant: about 2-3.5” across
Bloom Period: June, July, and August
Foliage: Green, ascending, wavy margins, smooth underneath, 3-6” long
Fall Color: N/A
Fruit Notes: Smooth green pod – 3-4” long, opens to release brown seeds, wind dispersal

Suggested Uses:

Sullivant’s Milkweed is native to wet prairies in Wisconsin in areas with full sun and moist to wet soil. Due to the considerable loss of prairie habitat in our state, Sullivant’s Milkweed is designated by the state of Wisconsin as a threatened species.

Although it is aesthetically very similar to Common Milkweed, its spread is much slower and much more manageable. Asclepias sullivantii can hybridize with Asclepias syriaca (Common Milkweed). Sullivant’s Milkweed is usually short and produces fewer umbels of flowers. The flowers of Sullivant’s Milkweed are slightly larger, and the underside of the leaves are hairless compared to Common Milkweed.

Restoration: A large percentage of Wisconsin was once prairie. Thankfully, the public’s mindset is changing, and more organizations and individuals want to restore what once was. Plant Sullivant’s Milkweed to provide biodiversity and attract pollinators.

Erosion: With its deep taproot, the soil is stabilized, helping reduce erosion.

Rain Garden/Pollinator Garden: As a lover of moisture and pollinator magnets, Sullivant’s Milkweed is an excellent addition to a pollinator or rain garden.

Wildlife Value:

All milkweeds are an extremely valuable food source for many insects. Bumblebees, cuckoo bees, leaf-cutting bees, and long-tongued bees are the most effective at cross-pollinating flowers.

Sullivant’s Milkweed is a larval food source for the Milkweed Tussock moth, Monarch butterfly, and Delicate Cycnia moth.

The Regal Fritillary, Monarch butterfly, Coral Hairstreak, Two-spotted Skipper, and several species of ants and bumblebees, as well as the Ruby-throated Hummingbird, drink the nectar.

Katydids, Tree Crickets, Grasshoppers, Aphids, Milkweed Bugs, Leaf-miner flies, Milkweed Stem Midge, Mealybugs, Weevils, Leaf Beetles, and Long-horned Beetles eat the leaves and/or flower buds.

Maintenance Tips:

Site plants properly as they develop deep taproots which make transplanting difficult.

Sullivant’s Milkweed can spread by rhizomes, occasionally producing offsets. Common Milkweed produces many more offsets and can be more difficult to control as a result. Simply pull out these offsets if it is necessary to keep the population under control.


Black Walnut Tolerant: Yes
Deer Resistant: Yes
Rabbit Resistant: Yes

Aphids will likely inhabit the plant – this is normal, natural, and part of the prairie ecosystem. There is no need for removal or pesticides as this will affect other eggs that have been laid on the plant by other beneficial pollinators.

Leaf Lore:

Sullivant’s Milkweed is named after William Starling Sullivant (1803 – 18873), an American botanist noted for naming more than 270 species of bryophytes (mosses and liverworts).

Milkweed is toxic to livestock and domestic animals. The plant contains cardenolides (cardiac glycosides), which effectively cause electrolyte imbalances, resulting in arrhythmias and cardiac failure.

Companion Plants:

For wetter, sunny, mesic sites plant alongside:

For pollinator gardens combine with:

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