The butterfly milkweed reaches 20 to 60 centimeters in height. Unlike other milkweeds, whose leaves appear in opposing pairs on the stem, the leaves of this species are laid out spirally. Its inflorescences, made up of multiple flowers, are also distinguished by their vibrant orange-yellow flowers. This species likes chalky soil, and is not shade-tolerant. It can be found in open, rocky, dry environments, like chalky shorelines and alvars.
Three varieties of the species exist in North America. The species is found all over the U.S., but only the interior variety (Asclepias tuberosa var. interior) can be seen in Canada, in a few locations in southern Ontario and western Québec.
In Québec this plant is very rare. It can be found at two sites, one of them described as “historical” since the species is now considered to have vanished from there.
The low quantity of individuals on Québec territory, the rarity of its habitat and the potential threat that specimens will be picked for medicinal and horticultural purposes justified designation of Asclepias tuberosa var. interior as an endangered species in Québec in 2005.
It is now protected under the provincial Act respecting threatened or vulnerable species. With the aim of safeguarding the only existing population in Québec, that law prohibits the sale of this species in the province in order to prevent their being collected in the natural environment.
To learn more
Butterfly milkweed, a species designated threatened in Québec (in French).