Interior Butterfly Weed
Asclepias tuberosa subsp. interior Woodson
The butterfly weed of the interior, and the one most people grow. It is the commonest subspecies west of the Appalachians and the source of most nursery stock.
How to tell it apart
Leaf bases are blunt, squared off or heart-shaped where they meet the stalk, and the leaves are narrower. Plants are 30 to 90 cm.
Compare with subsp. tuberosa and subsp. rolfsii. Everything else about the plant, including how to grow it and what it is worth to monarchs, is on the butterfly weed page.
Where it grows
By far the most widespread of the three, running from Ontario and Quebec south to the Gulf and west into Arizona, New Mexico and Utah, with scattered populations reaching the Atlantic coast. Orange and yellow flowers predominate in the western states, which is where the yellow seed strains sold as cultivars come from. It is rare enough in Quebec to be of conservation concern there.
Distribution follows the Flora of North America treatment, United States only. Butterfly Weed as a whole is recorded in 43 states.
Flowering
Interior Butterfly Weed blooms May to September, peaking in June and July. Plants reach 1 ft–2.9 ft.
Other names
This plant has also been published as Asclepias tuberosa var. interior, Asclepias tuberosa subsp. terminalis. Those names refer to the same taxon and you will meet them in older floras and in some databases.
References
The description, distribution and synonymy here follow Mark Fishbein’s treatment of Asclepias in Flora of North America vol. 14 (2023).
Cite this page
This page is licensed CC BY 4.0. Quote it, adapt it and reuse it, including commercially, as long as you credit Milkweed USA and link back.
Milkweed USA. (2026). Interior Butterfly Weed (Asclepias tuberosa subsp. interior). Retrieved DATE, from https://milkweedusa.com/species/butterfly-weed/interior/
"Interior Butterfly Weed (Asclepias tuberosa subsp. interior)." Milkweed USA, 2026, https://milkweedusa.com/species/butterfly-weed/interior/. Accessed DATE.
Milkweed USA. "Interior Butterfly Weed (Asclepias tuberosa subsp. interior)." Last modified 2026-08-01. Accessed DATE. https://milkweedusa.com/species/butterfly-weed/interior/.
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title = {Interior Butterfly Weed (Asclepias tuberosa subsp. interior)},
author = {{Milkweed USA}},
year = {2026},
url = {https://milkweedusa.com/species/butterfly-weed/interior/},
note = {Accessed DATE}
}