Milkweed is a whole genus of about 140 species of herbaceous perennial flowering plants, scientifically known as Asclepias. These plants are found throughout North and South America, and many of them are cultivated as ornamentals. Its genus name “Asclepias” refers to the Greek god of medicine Asklepios.
Milkweed grows quickly to two to four feet in height. It has a narrow vertical growth habit. Most species are toxic to humans and many other species.
Most milkweeds have white latex (milky sap), but some have clear sap. This is where the name “milkweed” comes from. The leaves are simple, most commonly opposite; the blades are variously shaped but are often somewhat wavy. They have unique flowers with five united petals, pod-like fruits, and tufted seeds that aid in wind dispersal.
Flowers can be yellow, orange, red, pink, purple and white. Milkweed is best known for being the exclusive food source for the larvae of monarch butterflies. It also provides nectar for bees, wasps, and butterflies.
Milkweed produces hundreds of fluffy seeds, which are distributed widely by the wind. In fact, each milkweed seed has a parachute, or pappus, which helps it travel farther. Seeds quickly germinate and form deep and extensive root systems. Those seeds that don’t immediately germinate can remain viable for months, even in water. In addition, milkweed is tolerant of many herbicides. All of these characteristics make it a difficult weed to eradicate.
Milkweed Varieties
- Tropical milkweed (Asclepias curassavica)
- Showy milkweed (Asclepias speciosa)
- Swamp Milkweed (Asclepias Incarnata)
- Antelope horns (Asclepias asperula)
- Cedar Hill milkweed (Asclepias lanceolata)
- Oval-leaved Milkweed (Asclepias Ovalifolia)
- White Swamp Milkweed (Asclepias Perennis)
- Purple Mikweed (Asclepias Purpurascens)
- Common Milkweed (Asclepias syriaca)
- Butterfly Milkweed (Asclepias tuberosa)
- Wheel Milkweed (Asclepias Uncialis)
- Redring Milkweed (Asclepias variagata)
- Green comet milkweed (Asclepias Viridiflora)
- Green Antelopehorn (Asclepias viridis)
- Whorled milkweed (Asclepias verticillata)
- Fourleaf Milkweed (Asclepias quadrifolia)
- Welsh’s milkweed (Asclepias welshii)
- Rush milkweed (Asclepias subulata)
Description And Pictures
Tropical milkweed (Asclepias curassavica)
The tropical milkweed is native to the American tropics and has a pantropical distribution as an introduced species. The flowers are in cymes with 10-20 flowers each. They have purple or red corollas and corona lobes that are yellow or orange. Flowering occurs nearly year-round.
Unlike the milkweed species native to certain locations, tropical milkweed does not go dormant in the winter, causing non-migratory groups of butterflies to form. It’s also known for its thin stems and an open form, which makes it look best mixed with other tall plants.
Other common names include bloodflower,cotton bush, hierba de la cucaracha, Mexican butterfly weed, redhead, scarlet milkweed, and wild ipecacuanha.
Showy milkweed (Asclepias speciosa)
This is a hairy, erect perennial growing up to 47 inches in height with large, oval, blue-green leaves arranged oppositely on stalks. It is found in the western half of North America. It has a fragrant pinkish-white flowers that bloom in spherical clusters from late spring to early summer.
Showy milkweed grows up to 3 feet tall when planted in moist, well-draining soil in a sunny spot. It has a rough, weedy perennial appearance with gray-green leaves and stems that are covered in velvety hairs.
This species is not listed as a noxious weed by the federal government or any state in the United States. However, it does spread vigorously by rhizomes, so it may not be a good choice for small, formal gardens where it could overwhelm smaller plants.
Swamp Milkweed (Asclepias Incarnata)
Swamp Milkweed is commonly found in wet meadows, swamps, river bottomlands, and wet areas throughout the United States and Eastern Canada. It grows to a height of 3 to 5 feet and spreads 2 to 3 feet wide. It has narrow, lance-shaped leaves.
The plants bloom in early through mid-summer, producing small, fragrant, pink to mauve (sometimes white) colored flowers in rounded umbellate racemes. The flower color varies from darker shades of purple through soft, pinkish purple, and a white flowering form exists as well.
Antelope horns (Asclepias asperula)
The Antelope horns also known as spider milkweed, is native to the Southwestern United States and northern Mexico. This milkweed gets its name from the seed pods that resemble the horns of antelope. You can easily spot the flower clusters (technically, umbellate cymes) in open meadows.
The plant is low-growing, not exceeding 2 feet in height, and is characterized by its long, narrow leaves that fold upward from a central vein. The flowers are greenish-yellow with maroon highlights and bloom in clusters from April to June.
Asclepias asperula is divided into two subspecies:
- A. asperula. ssp. asperula
- A. asperula ssp. capricornu.
Ssp. capricornu occurs in comparatively more mesic conditions and has comparatively broader leaves, floral crowns that are more white, and a more prostrate habit. Ssp. asperula occurs in comparatively more arid conditions and has comparatively narrower leaves, floral crowns that are more purple, and a more upright habit.
Cedar Hill milkweed (Asclepias lanceolata)
Cedar Hill milkweed also referred to few-flowered milkweed is native to the coastal plain of the United States from New Jersey to Florida and Southeast Texas. It is commonly referred to as Cedar Hill milkweed, because it was first described by Dr. Eli Ives in the neighborhood of Cedar Hill in New Haven, Connecticut.
It is an upright plant that can grow between 3 and 5 feet tall. Its clusters of bright orange-red flowers that bloom in the summer months, typically from May to August. The flowers are arranged in umbels (flat-topped clusters) at the ends of the stems, with 1-3 umbels per plant. The flower hoods extend well above the stigmatic disc, and the horns are prominent and curved inward.
They call it Fewflower milkweed because it usually has 5-12 bright orange-yellow flowers adorned with a red corolla. It can be frequently found in marshes (fresh and brackish), low glades, and wet pine barrens.
Oval-leaved Milkweed (Asclepias Ovalifolia)
This lesser-known milkweed species blooms in late May to early July. The flowers are white and produced in several umbels (a cluster of flowers stalks arising from a common point). Like many other milkweed species, the oval-leaved milkweed is toxic to humans and animals if ingested in large quantities.
The plant is upright, but short, and has just a few pairs of oval leaves along the stem. The leaves are on short stalks and have no teeth along the margins. Fertilized flowers produce erect follicles (seed pods) that are covered in fine hairs and held upright.
The oval-leaved milkweed is native to prairies and savannas. It is rare in the eastern portion of its range in Illinois and Wisconsin, but more prevalent, although still uncommon, in Iowa, Minnesota, and the Dakotas. It is mostly found in remaining high quality natural areas and prefers open sun and frequent wildfire.
Common Milkweed (Asclepias syriaca)
Origin: Eastern and central North America, from Canada to the U.S. Midwest.
Common Milkweed grows 3-6 feet tall in zones 3-9, with broad, oval leaves and large, spherical clusters of fragrant, pink-to-purple flowers blooming June to August. Found in fields and roadsides, it thrives in full sun with average soil, spreading via rhizomes. Its milky sap and robust seed pods make it a monarch favorite, though it can be weedy in gardens.
Butterfly Weed (Asclepias tuberosa)
Origin: Eastern and southern U.S., from New England to Texas.
Butterfly Weed, a compact 1-3 footer in zones 3-9, boasts bright orange (sometimes yellow) flower clusters from June to September. Its narrow, hairy leaves lack milky sap, and it prefers dry, sandy soils in full sun. Drought-tolerant and deer-resistant, it’s a vibrant, non-invasive choice for pollinator gardens.
Whorled Milkweed (Asclepias verticillata)
Origin: Central and eastern U.S., from Texas to New England.
Whorled Milkweed reaches 1-3 feet in zones 4-9, with fine, needle-like leaves in whorls and small, white-to-greenish flowers blooming May to September. Thriving in dry, sunny prairies, it’s delicate yet hardy, supporting monarchs with its toxic sap. Its slender seed pods add airy charm.
Purple Milkweed (Asclepias purpurascens)
Origin: Eastern U.S., from New York to Georgia and west to Iowa.
Purple Milkweed grows 2-4 feet in zones 3-8, with broad leaves and rich magenta-purple flower umbels from May to July. It favors open woods and meadows with moist, well-drained soil and full sun. Less common than others, its striking color and monarch appeal make it a garden treasure.
Green Comet Milkweed (Asclepias viridiflora)
Origin: Central and eastern U.S., from Texas to New York.
Green Comet Milkweed, 1-3 feet tall in zones 4-9, features pale green, star-shaped flowers in loose clusters from June to August. Its lance-shaped leaves suit dry prairies and rocky soils in full sun. Subtle yet supportive for monarchs, it’s named for the comet-like look of its blooms.
Green Antelopehorn (Asclepias viridis)
Origin: South-central U.S., from Texas to Tennessee.
Green Antelopehorn grows 1-2 feet in zones 5-9, with broad leaves and pale green-to-purple flowers from May to August. Found in prairies and roadsides, it thrives in dry, sunny spots, producing curved seed pods. Its early bloom and monarch-friendly sap make it a southern staple.
Heartleaf Milkweed (Asclepias cordifolia)
Origin: Western U.S., from California to Oregon.
Heartleaf Milkweed reaches 1-2 feet in zones 7-10, with heart-shaped, waxy leaves and reddish-purple flower clusters from May to July. It prefers dry, rocky slopes in full sun, offering a striking contrast in western gardens. Its compact size suits rockeries and butterfly habitats.
Narrowleaf Milkweed (Asclepias fascicularis)
Origin: Western U.S., from California to Washington.
Narrowleaf Milkweed grows 2-4 feet in zones 6-10, with thin, whorled leaves and pale pink-to-white flowers from June to September. Thriving in dry, sunny meadows, it’s a key monarch host in the West, with slender pods releasing wind-borne seeds. It’s subtle yet essential.
Fourleaf Milkweed (Asclepias quadrifolia)
Origin: Eastern U.S., from New Hampshire to North Carolina.
Fourleaf Milkweed, 1-2 feet tall in zones 5-8, has whorled leaves (often four per node) and delicate, pink-to-white flowers from May to July. It favors dry, wooded slopes with part shade, adding a woodland charm. Its rarity and monarch support make it special.
Poke Milkweed (Asclepias exaltata)
Origin: Eastern U.S., from Maine to Georgia and west to Missouri.
Poke Milkweed reaches 3-5 feet in zones 3-7, with broad, drooping leaves and loose, white-to-pink flower clusters from June to August. Preferring shady woodlands and moist soil, it’s a tall, elegant option for forest edges, hosting monarchs with its toxic foliage.
Rush Milkweed (Asclepias subulata)
Origin: Southwestern U.S., from Arizona to California.
Rush Milkweed grows 2-4 feet in zones 9-11, with leafless, rush-like stems and creamy white-to-yellow flowers from spring to fall. A desert native, it thrives in arid, sunny conditions, supporting monarchs in harsh climates. Its minimalist look suits xeriscapes.
Broadleaf Milkweed (Asclepias latifolia)
Origin: Central and southwestern U.S., from Kansas to Arizona.
Broadleaf Milkweed, 1-3 feet tall in zones 5-9, features wide, oval leaves and greenish-yellow flower clusters from May to August. Found in dry prairies and plains with full sun, its sturdy form and monarch-friendly sap make it a resilient, understated choice.
California Milkweed (Asclepias californica)
Origin: California, U.S., from coastal hills to inland valleys.
California Milkweed grows 2-3 feet tall in zones 7-10, with woolly, gray-green leaves and purple-pink flowers blooming April to July. Thriving in dry, sunny hillsides, its fuzzy texture and early bloom support monarchs in the West. It’s drought-tolerant and perfect for native gardens.
Desert Milkweed (Asclepias erosa)
Origin: Southwestern U.S., from California to Utah.
Desert Milkweed reaches 2-4 feet in zones 8-11, with broad, hairy leaves and creamy yellow-to-green flowers from May to September. A desert native, it loves arid, sunny spots, producing large, curved pods. Its rugged charm aids monarchs in harsh climates.
Engelmann’s Milkweed (Asclepias engelmanniana)
Origin: Southwestern U.S., from Texas to Arizona.
Engelmann’s Milkweed grows 2-4 feet in zones 6-9, with narrow, lance-shaped leaves and pale green-to-yellow flowers from June to August. Found in dry prairies and rocky soils with full sun, it’s a subtle monarch host with slender, upright pods.
Mead’s Milkweed (Asclepias meadii)
Origin: Central U.S., from Missouri to Kansas.
Mead’s Milkweed, a rare 1-2 footer in zones 4-8, has smooth, narrow leaves and greenish-cream flowers from May to June. Preferring sunny prairies with well-drained soil, it’s a threatened species vital for monarchs, needing conservation efforts to thrive.
Prairie Milkweed (Asclepias sullivantii)
Origin: Central U.S., from Minnesota to Texas.
Prairie Milkweed grows 2-3 feet in zones 3-7, with thick, broad leaves and vibrant pink-to-purple flowers from June to August. Thriving in moist prairies and full sun, its sturdy form and sweet scent make it a monarch-friendly prairie staple.
Spider Milkweed (Asclepias asperula ssp. capricornu)
Origin: Southwestern U.S., from Texas to California (distinct from A. asperula).
Spider Milkweed, 1-2 feet tall in zones 7-10, features wide, wavy leaves and greenish-yellow flowers with purple tips from April to July. Found in dry, rocky soils with sun, its sprawling habit and curved pods support desert monarchs.
Tall Green Milkweed (Asclepias hirtella)
Origin: Central and eastern U.S., from Kansas to Kentucky.
Tall Green Milkweed reaches 2-4 feet in zones 4-8, with thin, hairy leaves and green-to-white flowers from June to August. Growing in sunny prairies and meadows, its delicate clusters and monarch appeal add subtle grace to open spaces.
Velvetleaf Milkweed (Asclepias tomentosa)
Origin: Southeastern U.S., from Florida to Texas.
Velvetleaf Milkweed grows 1-3 feet in zones 8-10, with soft, velvety leaves and pale yellow-to-green flowers from May to August. Thriving in sandy, sunny pinelands, its fuzzy texture and monarch support make it a southern charmer.
Wheel Milkweed (Asclepias uncialis)
Origin: Southwestern U.S., from Arizona to Texas.
Wheel Milkweed, a tiny 6-12 inches in zones 7-9, has small, oval leaves and pinkish-purple flowers from April to June. A rare desert dweller, it prefers dry, rocky soils in full sun, offering monarchs a petite but potent host.
Woolly Milkweed (Asclepias vestita)
Origin: California, U.S., from the Sierra foothills to deserts.
Woolly Milkweed grows 1-2 feet in zones 7-10, with woolly, gray-green leaves and creamy white-to-pink flowers from April to July. Found in dry, sunny scrublands, its soft fuzz and monarch-friendly sap suit arid native gardens.
Zizotes Milkweed (Asclepias oenotheroides)
Origin: Southwestern U.S. and northern Mexico, from Texas to Arizona.
Zizotes Milkweed reaches 1-3 feet in zones 7-10, with broad, wavy leaves and greenish-white flowers from May to September. Thriving in dry, sunny plains, its upright pods and monarch support make it a resilient desert option.
Redring Milkweed (Asclepias variegata)
Origin: Southeastern U.S., from Texas to Maryland.
Redring Milkweed grows 1-3 feet in zones 6-9, with glossy leaves and white flowers with red-purple rings from May to July. Favoring woodlands with part shade, its elegant blooms and monarch appeal shine in shaded gardens.