Species At Risk

Four-leaved Milkweed

(Asclepias quadrifolia)


Four-leaved Milkweed
Four-leaved Milkweed occurrences map


The Four-leaved Milkweed is a leafy, perennial plant, one of the smallest of the North American representatives of the milkweed genus. It grows 20 to 80 centimetres tall. Four-leaved Milkweed has leaves that are arranged in opposite pairs, and has clusters of small, pinkish-white flowers. This plant flowers from late May till the end of June. Pollination is mostly by bees and butterflies. Seeds have dense tufts of silky white hairs to aid in wind dispersal, and are contained in long, narrow seed pods on mature plants.

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Four-leaved Milkweed is at the northern limit of its range in Ontario and New England. There are only two known populations remaining in Ontario, both in Prince Edward County. Historically, populations have also been recorded from the neighbouring Lennox and Addington County, as well as from the Niagara River gorge.


Four-leaved Milkweed typically occurs on dry to somewhat moist, shallow or rocky soils over limestone, or sometimes sandstone, bedrock within mature deciduous woodlands and sometimes in forests, thickets or meadows. In Ontario, it is found in two types of habitat: (1) dry woodlands dominated by Tallgrass prairie herbs, Bur Oak and Shagbark Hickory, and (2) a woodland alvar dominated by Red Cedar and pasture grasses, which was probably created by human activities.


Threats to the remaining populations of Four-leaved Milkweed in Ontario include habitat loss due to residential and agriculture land uses, and invasive plant species.


Four-leaved Milkweed receives protection under Ontario’s Endangered Species Act.

What You Can Do to Help Four-leaved Milkweed

  • The Ministry of Natural Resources tracks species at risk such as Four-leaved Milkweed. You can use a handy online form to report your sightings to the Natural Heritage Information Centre. Photographs with specific locations or mapping coordinates are always helpful. nhic.mnr.gov.on.ca
  • Report any illegal activity related to plants and wildlife to 1-877-TIPS-MNR (847-7667).
  • Private land owners have a very important role to play in species at risk recovery. If you find Four-leaved Milkweed on your property, you may be eligible for stewardship programs that support the protection and recovery of species at risk and their habitats.
  • Volunteer with your local nature club or provincial park to participate in surveys or stewardship work focused on species at risk.
  • Four-leaved Milkweed are pollinated by bees and butterflies. Pollinators are in steep decline across the globe and they play a key role in the survival of many of Ontario’s rare plants. For information on how you can help scientists monitor pollinator populations in Ontario visit: www.seeds.ca/proj/poll.
  • Invasive species seriously threaten many of Ontario’s species at risk. To learn what you can do to help reduce the threat of invasive species, visit: ontario.ca/invasivespecies; www.invadingspecies.com; www.ontarioinvasiveplants.ca; and, www.invasivespecies.gc.ca.

Did you know?

The milkweed family gets its name from its milky juice.

Did you know?

The scientific name for the milkweed genus, Asclepias, is taken from Asclepius, the Greek god of healing, because of the many folk-medicinal uses for milkweed plants.

Did you know?

The two populations of Four-leaved Milkweed which are known to still exist in Ontario were only recently discovered – in 2006 and 2007. It is possible that additional populations may be identified in the future.

The Endangered Species Act

Contact your local ministry office

Often the best source of local information on species at risk is your nearest ministry office. Call with your questions or concerns.