Iowa wildflower Wednesday: Tall green milkweed

Of the seventeen milkweed plants (Asclepias genus) that are native to Iowa, only five are widespread in our state: common milkweed, swamp milkweed, butterfly milkweed, whorled milkweed, and sand milkweed.

Today’s featured plant, Tall green milkweed (Asclepias hirtella), is considered “scarce” rather than endangered or threatened in Iowa. Its native range includes parts of eighteen states from the Gulf of Mexico to the Great Lakes, plus the Canadian province of Ontario. According to the Illinois Wildflowers website, preferred habitats have exposure to full sun, with “moist to dry conditions, and sandy or gravelly soil,” including “dry-mesic railroad prairies, sand prairies, rocky glades, edges of sandy wetlands, roadsides, pastures, and abandoned fields.” This species is sometimes known as prairie milkweed.

Tall green milkweed plants typically reach a height between one and three feet, so aren’t particularly tall compared to some summer wildflowers on the prairie, such as compass plant or cup plant. But it’s taller than a related species called green milkweed ( Asclepias viridiflora). The Minnesota Wildflowers site advises that flowers of Asclepias hirtella “are different enough to avoid confusion, plus A. viridiflora is typically a shorter plant with less densely packed leaves.”

I’ve never seen tall green milkweed in the wild, so relied on other photographers for all of the images enclosed below.

One way of grouping milkweed plants is by the shape of their leaves: broad, narrow, or slender. Tall green milkweed is in the “slender” category (like whorled milkweed).

U.S. Fish & Wildlife Service staff at the Port Louisa National Wildlife Refuge along the Mississippi River in Louisa County gave Bleeding Heartland permission to publish this lovely photo by Jessica Bolser. It originally appeared on the refuge’s Facebook page in late July. You can see the slender leaves that alternate along the stem. Some umbels have many flowers in bloom, while others are still budding.

David Wehde took these pictures in July 2018 at a prairie relic in Johnson County. Some plants are flowering, while others already have follicles (seedpods) forming. As with other milkweeds, “Each follicle contain numerous seeds with tufts of white hair that are released to the wind at maturity.”

A closer view of tall green milkweed flowers, courtesy of David Wehde:

Andy Kellner found this tall green milkweed plant blooming in Ringgold County in June 2018.

Top image: Cropped from a photo by Jessica Bolser of the U.S. Fish & Wildlife Service, taken at the Port Louisa National Wildlife Refuge in July.

Tags: Wildflowers
  • It's fun to see this plant again

    I saw tall green milkweed years ago, growing in a southern Iowa prairie, and later I was part of a field trip that found many more tall green milkweeds in a couple of northern Missouri prairies. The plants looked very enthused, as if they were sort of exploding in all directions. These photos, especially the last Kellner photo, capture that exuberant look. Milkweeds are great.

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