Common Milkweed

Scientific Name: Asclepias syriaca. The genus Asclepias refers to Asklepios, the Greek god of medicine. The species name, syriaca, is a reference to Syria. It seems like there was some confusion in naming this plant which is native to North America, not Syria!^4,5

Common Name: Common milkweed. Milkweed plants get their name from the milky sap which oozes out when leaves or the stem are cut. Other names for this plant include Virginia-silk and silky swallowwort. What part of the plant do you think silk refers to? Perhaps the silky hairs attached to the seeds?^4,6

Family: Apocynaceae (Dogbane Family). A family with 4,800 species that are primarily found in tropical and subtropical regions, except for a few genera which are found in temperate areas. The plants may be trees, shrubs, woody vines, or herbs, and the vast majority have milky, poisonous sap. The alkaloids and cardiac glycosides that make many of these species toxic also make them medicinally useful. Leaves are usually opposite and untoothed. Flowers typically have 5 sepals, 5 petals, and 5 stamens. Fruits are often dry pods that split open to release the ripe seeds. A number of flowering plants of the dogbane family are used in landscaping, such as oleander (Nerium oleander), periwinkle (Vinca spp.), and frangipani (Plumeria spp.).

Average Height: 3-5 feet

Description: A perennial plant that may spread easily through its rhizomes, forming large colonies. The stout stem is pale green and usually has short hairs. The oblong, untoothed leaves measure up to 8” long and 3½” wide. The medium green leaves have reddish veins and are nearly hairless above, with dense, matted hairs below. Stems and leaves ooze a milky sap when cut or crushed. Leaves grow opposite each other on the stem, and 2–6 flower heads grow from near the base of the upper leaves and from the end of the stem. The ball-like flower heads measure 2–4” across and may have up to 100 individual pink to purple flowers that measure about ¼” across. Each flower has 5 petals that are bent backwards, plus 5 horn-like hoods. Warty seed pods are 3–4” long and covered in short hairs. Seed pods split open on one side to release the mature seeds, which float away on silky tufts of hair that are carried by the wind.^3,4,5,6,7,9

Bloom time: Jun – Aug

Notes: There are a total of 15 species of milkweeds (Asclepias spp.) growing in Virginia. The size and shape of the leaves vary, and while the flowers vary in color from white to pink to purple to orange, the shape of their individual flowers is similar to those of Asclepias syriaca.³

Range: Common throughout the entire state of Virginia.² Most common in states from Maine to North Dakota south to Kansas and east to North Carolina. Less frequent in southern states, from Oklahoma and Louisiana east to South Carolina and Georgia (but not Florida), and introduced in several western states like Montana, Utah, and Oregon. Present in Canada from New Brunswick to Saskatchewan.¹

Geology/Soil: Prefers rich, moist, loamy, and well-drained soils, but also does well in drier soils and drought conditions. May be found in rocky, sandy, or clayey calcareous soils.^4,6,7,9

Habitat: Prefers sunny locations on roadsides, in fields, along edges of water or forests, and disturbed habitats.^2,5,6

Flora associations: Often found growing in open, disturbed places with plants such as Pennsylvania blackberry (Rubus pensilvanicus), broomsedge (Andropogon virginicus), hemp dogbane (Apocynum cannabinum), purpletop (Tridens flavus), annual fleabane (Erigeron annuus), tall goldenrod (Solidago altissima), and horse-nettle (Solanum carolinense).

Fauna associations: Common milkweed is always hopping with action, with over 450 species of insects that eat parts of it! Many insects are drawn to the sweet nectar, including bees, wasps, butterflies, beetles, ants, and more! What do you see visiting these milkweeds? The monarch butterfly (Danaus plexippus) caterpillars depend on the leaves of common milkweed for food, and the toxins in the plant protect the butterfly by making it toxic too. If you are lucky, you may see a green chrysalis with a golden band hanging from the leaves and know that a monarch butterfly will soon emerge. Among the many other species which feed on Asclepias syriaca are the red milkweed beetle (Tetraopes tetraophthalmus), the milkweed tussock moth (Euchaetes egle), and the seed-eating large and small milkweed bugs (Oncopeltus fasciatus and Lygaeus kalmii). The toxic, bitter leaves are unpalatable to white-tailed deer and other mammals.^5,9

Human associations: Over time, humans have found a wide variety of medicinal and other uses for Asclepias syriaca. The tough fibers in the stems of the milkweed are used to make ropes, bowstrings, or even coarse cloth. Many Indigenous people eat the young sprouts, tender leaves, and/or flower buds. The Cherokee, Rappahannock, and Haudenosaunee use the sap to treat warts and ringworm. It has also been used as a laxative, gynecological aid, and even a contraceptive. Although they have some medicinal uses, milkweeds contain cardiac glycosides, alkaloids, and other substances that make them poisonous to humans! The fluffy tufts of hair attached to the seeds have been used for everything from life jackets in World War II to pillows and blankets.^6,7,10

We want these plants to thrive and for everyone who gets to visit the park to enjoy them, so remember – don’t pick flowers or other parts of the plant!!

1 “2014 BONAP Maps by States and Provinces: County Distribution Map of Asclepias Syriaca – Common Milkweed.” Bonap.net, 14 Dec. 2014, bonap.net/FieldMaps/Home/SingleMap?taxonId=1407&mapType=County. Accessed 10 Jan. 2025.

2 “Digital Atlas of the Virginia Flora | Asclepias Syriaca L.” Vaplantatlas.org, 2025, www.vaplantatlas.org/index.php?do=plant&plant=2026&search=Search. Accessed 10 Jan. 2025.

3 Weakley, A.S., J.C. Ludwig, and J.F. Townsend. 2012. Flora of Virginia. Bland Crowder, ed. Foundation of the Flora of Virginia Project, Inc., Richmond. Fort Worth: Botanical Research Institute of Texas Press, pp. 252-262.

4 “Asclepias Syriaca – Plant Finder.” Www.missouribotanicalgarden.org, www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=b480. Accessed 10 Jan. 2025.

5 Taylor, David . “Common Milkweed.” Www.fs.usda.gov, www.fs.usda.gov/wildflowers/plant-of-the-week/asclepias_syriaca.shtml. Accessed 10 Jan. 2025.

6 Stevens, Michelle, and M. Kat Anderson. “Plant Guide: COMMON MILKWEED.” United States Department of Agriculture Natural Resource Conservation Service, https://plants.usda.gov/DocumentLibrary/plantguide/pdf/pg_assy.pdf. Accessed 10 Jan. 2025.

7 “Asclepias Syriaca (Common Milkweed) | North Carolina Extension Gardener Plant Toolbox.” Plants.ces.ncsu.edu, plants.ces.ncsu.edu/plants/asclepias-syriaca/. Accessed 10 Jan. 2025.

8 “Apocynaceae | Description, Major Genera and Species, & Facts.” Encyclopedia Britannica, www.britannica.com/plant/Apocynaceae. Accessed 10 Jan. 2025.

9 “Common Milkweed (Asclepias Syriaca).” Illinoiswildflowers.info, 2019, www.illinoiswildflowers.info/weeds/plants/cm_milkweed.htm. Accessed 10 Jan. 2025.

10 “BRIT – Native American Ethnobotany Database.” Brit.org, 2025, naeb.brit.org/uses/search/?string=asclepias+syriaca. Accessed 10 Jan. 2025.

Definitions:

Rhizome: A horizontal, underground stem from which new plant may grow.