Asclepias incarnata

Asclepias incarnata, (Swamp Milkweed)

General Description

A. incarnata is commonly referred to as swamp milkweed because of its association with highly saturated soils in wetlands or areas that are flooded seasonally. Plants usually have a taproot with the root crown producing one to six or more stems each growing season. The flowers, which are said to give off a scent similar to cinnamon, are presented on medium sized erect umbels that tend to be flat. Swamp milkweed is self-compatible which contrasts with the self-incompatibility of other studied milkweeds.

Fun Fact: In the past, the roots of swamp milkweed were simmered to make a tea taken in small quantities both as a general purge and to destroy and expel parasitic worms.


Distribution: AL, AR, CO, CT, DC, DE, FL, GA, IA, ID, IL, IN, KS, KY, LA, MA, MD, ME, MI, MN, MO, MT, NC, ND, NE, NH, NJ, NM, NV, NY, OH, OK, PA, RI, SC, SD, TN, TX, UT, VA, VT, WI, WV, WY

Canada: MB, NB, NS, ON, PE, QC

Flower: Color is generally light pink to light purple but seeds of a reddish form known as pulchra are sold for gardens. Similarly, white variants are found in the wild and are sold by nurseries. 20+/- flowers per umbel.

Foliage: Texture is course, color is green, and plant stands erect. The leaves on plants exposed to full sun are often purplish toward the end of the growing season. Leaf arrangement is opposite and attachment is petiolate.

Growth Period: Spring.

Habitat: Most often found on the margins of flooded plains, lakes, ponds, waterways, marshes, swamps, and other wet areas.

Height: 2-5 ft (60-152 cm).

Leaves: Long and narrow and taper off to a point, 2 3/4 – 6 in (7-15 ¼ cm) long and 1/2 – 1 in (1- 2 ½ cm) wide. Glabrous.

Roots: Some are shallow rooted but known to have taproots of 18 inches or more.

Toxicity: High, but will not seriously harm humans if a small quantity is consumed.


Blossoming Season: Late summer to early fall in wild populations. Tends to bloom twice in a growing season when in gardens.

Life span: In gardens most plants live two-five years but known to survive up to 20 years.

Propagation: Slow to spread via seeds.

Pods: Erect, long 4 in (10 cm) and narrow like the leaves.  The pods are often in pairs.

Seed Color: Brown, 5/16 in (8 mm) long.

Environment and Growth Requirements

Maintenance: Low.

Overhead Conditions: Not shade tolerant. An early successional plant that tends to grow at the margins of wetlands and in seasonally flooded areas. It is not a good vegetative competitor and tends to disappear as vegetative density increases and habitats dry out.

Precipitation: Not drought tolerant. 20 – 65 in (51-165 cm) annually.

Soil Texture: Grows in fine to medium soils.  Soils need to by moist.

Temperature: Survives in areas with minimum temperature of -38 Fahrenheit (-39 Celsius).

Work Cited:,,,,,, (A Second Ohio Weed Manual)

Photos: Monarch Watch Archive