Asclepias

( ass - KLEEP - ee - ass )

At-A-Glance Information

Commonly called Milkweed, this genus is filled with species of flowering plants that need full sun and moderate water to perform well in the landscape. These flowers are considered easy-to-grow garden plants whose nectar will attract butterflies and other beneficial insects and pollinators to the garden. They bloom in early summer, with many star-like small flowers that bloom in clusters in a range of colors including white, pink, yellow, and orange. Inflated seedpods will split when ripe to reveal silky seeds and milky sap. Take care when planting Milkweed in the garden, as all parts are poisonous to humans and pets if ingested.

Asclepias Species and Varietals

The genus Asclepias includes over 200 species, and is a member of the plant family Apocynaceae. The genus was first formally described by Carl Linnaeus in 1753, and was named after the Greek God of healing, Asclepius. The best growing zones for Milkweed depend on the species cultivated. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Asclepias albicans (Whitestem Milkweed, Wax Milkweed, White-Stemmed Milkweed)
This species is native to California, Arizona and Baja Mexico and grows best in USDA hardiness zones 9-11. It forms a spindly shrub that produces young branches clothed in wax (hence the common name Wax Milkweed). Flowers bloom in inflorescences throughout the entire year and are purple-tinted green with cream to white sepals. Individual plants reach up to 3-4 feet tall (exceptionally to 13 feet) and just as wide at maturity.

Asclepias amplexicaulis (Blunt-Leaved Milkweed, Clasping Milkweed, Sand Milkweed)
This species is endemic to the United States, found mostly in areas east of the Great Plains. It prefers to grow in dry savannas, open woods, prairies, and fallow fields in sandy soil. Plants in this species typically reach up to 1-3 feet tall and form stout, erect stems with large, wavy-margined green leaves. Flowers are smoky purple to greenish-blue and bloom in late spring through early summertime. Grows well in USDA zones 3-9.

Asclepias angustifolia (Arizona Milkweed, Narrow-Leaved Milkweed, Slender Milkweed)
This species is native to Arizona, and is a cold-hardy species (good to -12 degrees Fahrenheit). These plants grow well in USDA hardiness zones 8-10. Flowers are white to pink, and these plants grow well in rocky soils. Arizona Milkweed naturally grows in woodland areas, floodplain meadows and amongst canyons.

Asclepias asperula (Antelope Horns Milkweed, Spider Milkweed, Green-Flowered Milkweed)
This species of Milkweed is native to the southwestern United States and northern Mexico, and is a very commonly-encountered species in Texas. Spider Milkweed grows well in USDA zones 7-9. These plants favor very fast-draining, rocky soils and because of their deep taproot do not perform well when cultivated in containers.

Asclepias californica (California Milkweed)
This unique species of Milkweed has light green, wooly foliage and produces dark purple to reddish flowers. It is endemic to California, where it grows on well-draining rocky slopes. The species does well in USDA hardiness zones 7-10. Individual plants reach up to between 2-3 feet tall and 1-5 feet wide.

Asclepias cinerea (Carolina Milkweed, Ashy Milkweed)
This species is native to the southeastern United States, and is a perennial herb with grassy foliage. Flowers range in color from ash gray to purple to rose-pink. Plants reach up to 2 feet tall when mature and in bloom.

Asclepias connivens (Baldwin's Milkweed, Largeflower Milkweed)
This species grows mostly in Alabama, Georgia, and Florida, and is at home in wetland areas. It was first identified by American botanist William Baldwin in 1817. The specific epithet 'connivens' refers to the conniving (converging) hoods over the flower stigma. These plants die back to the ground in wintertime and emerge the following spring. Baldwin's Milkweed grows well in USDA hardiness zones 8-11.

Asclepias cordifolia (Heart-Leaf Milkweed, Purple Milkweed)
This species is native to the western United States, namely California, Nevada, and Oregon, growing well in USDA hardiness zones 7-10. Flowers are dark reddish-purple, and bloom from May through July. Individual plants reach up to between 1 and 3 feet tall when mature and in bloom, and produce green to grey-green foliage.

Asclepias cryptoceras (Jewel Milkweed, Pallid Milkweed, Humboldt Mountains Milkweed, Cow-Cabbage, Davis' Milkweed)
These plants are native to the Great Basin area, and love growing in dry areas. It is a low-growing species with a somewhat droopy habit, and produces clusters of small cream and purple flowers. These plants do well in USDA hardiness zones 4-7 and form plants that reach between just 4 and 12 inches tall at maturity.

Asclepias curassavica (Bloodflower, Tropical Milkweed, Hierba de la Cucaracha, Mexican Butterfly Weed, Scarlet Milkweed, Wild Ipecacuanha, Indian Root, Annual Milkweed, Redhead, Cotton Bush)
This species of Milkweed grows best in USDA hardiness zones 9-11 or Sunset growing zones 8, 9, 12-24, H1 and H2 as a perennial plant or in any zone as an annual. Native to South America, this woody-based plant has stiff stems to 3 feet tall and 2 feet wide. Flowers are vivid red. Variety 'Silky Gold' has bright yellow to yellow-orange blooms. Needs moderate amounts of water to perform well in the landscape. This species is considered invasive in many tropical and subtropical areas, including Asia, Australia, Africa, and parts of the United States.

Asclepias curtissii (Curtiss's Milkweed)
This species is endemic to sandy areas in Florida, and produces a plant with dark green leaves and bright white flowers that bloom in summertime. It is considered rare and is a protected species in its home state. Individual plants reach up to 2-4 feet tall at maturity when in bloom.

Asclepias eriocarpa (Woolypod Milkweed, Indian Milkweed, Kotolo)
These plants are covered in thick, white hairs and produce white to cream-colored flowers that are tinted with bright pink. Blooms pop from May through October. This species is native to California, Nevada, and Baja California, where it grows on rocky hillsides, woods, deserts, and other dry areas. Best in USDA hardiness zones 4-9.

Asclepias erosa (Desert Milkweed, California Desert Milkweed)
This species is native to California, Arizona, and northern Baja California, where it grows in desert areas, hence its common name. Yellow-green stems are fuzzy, and flowers are yellow to cream-colored. Plants reach up to between 4 and 18 inches tall when mature, and grow well in USDA hardiness zones 6-9. Hardy down to -10 degrees Fahrenheit.

Asclepias exaltata (Poke Milkweed, Tall Milkweed)
This species is native to eastern North America, and blooms from late spring through early summertime. These plants love to grow in moist woodland habitats, along shorelines, and at forest edges. They prefer soil to be kept moist, and to have partial sun exposure. These plants reach just under 5 feet tall. Flowers are green and white. Best in USDA zones 3-9.

Asclepias fascicularis (Narrowleaf Milkweed, Mexican Whorled Milkweed)
This species is native to a variety of habitats in the western United States and Baja California and grow well in USDA hardiness zones 6-10. These plants bloom from late spring through late summertime and produce light pink to white flowers, reaching up to between 2 and 3 feet tall and 1 to 3 feet wide at maturity.

Asclepias feayi (Florida Milkweed)
This wildflower species is native to Florida, as its common name suggests, and produces delicate white flowers. Plants emerge from winter dormancy in springtime, and produce blooms in the middle of summer. The species epithet honors physician and botanist William T. Feay. Plants reach up to 2 feet tall when mature.

Asclepias hirtella (Tall Green Milkweed, Green Milkweed, Prairie Milkweed)
This species is native to Canada and the United States, and grows well in open habitats with dry, sandy soils. Flowers are greenish to purple, and bloom June through August. They do well in USDA hardiness zones 4-9 and can reach up to between 1 and 3 feet tall when mature and in bloom.

Asclepias humistrata (Sandhill Milkweed, Pinewoods Milkweed, Pink-Veined Milk Plant, Fleshy Milkweed)
Native to the southeastern United States, this species blooms in spring and summer, producing pink-lavender-white shows of blooms. These plants prefer well-draining rocky soils and sandy woodland areas, and reach between 1 and 3 feet tall at maturity. Best in USDA zones 8 and 9.

Asclepias incarnata (Swamp Milkweed, Rose Milkweed, Rose Milkflower, Swamp Silkweed, White Indian Hemp, Marsh Milkweed, Swamp Butterfly Weed)
This native species of North America blooms in early to mid-summer, and has fragrant pink to mauve flowers. This species has many garden-grown cultivars available, and typically reaches 3-5 feet tall and 2-3 feet wide. Cultivars include 'Ice Ballet' (with white flowers on a compact plant), 'Cinderella' (with soft pink flowers and drought tolerance), and 'Soulmate' (with rose-purple flowers and a preference for drier soils).

Asclepias involucrata (Asclepias macrosperma) (Dwarf Milkweed, Large-Seed Milkweed)
This wildflower species of Milkweed is native to the southwestern United States and northern Mexico, where it grows well in mixed desert shrub and juniper woodland. These plants reach just 10 inches tall, hence their common name 'Dwarf Milkweed'.

Asclepias lanceolata (Fewflower Milkweed, Cedar Hill Milkweed, Red Milkweed, Coastal Milkweed)
This species was first described by Dr. Eli Ives and is found in coastal plains in the eastern and southern United States, growing well in USDA hardiness zones 7-11. These plants can reach between 3 and 5 feet tall and have reddish-orange flowers that bloom in summertime.

Asclepias lanuginosa (Wooly Milkweed, Sidecluster Milkweed)
This species is native to Canada and the midwestern United States, reaching about 12 inches tall at maturity. It was first described in 1818, and produces off-white to greenish flowers. Best in USDA hardiness zones 3a-7a.

Asclepias longifolia (Longleaf Milkweed, Savanna Milkweed)
This native of the southern United States is considered to be rare in the northern end of its native range. It has been declared extinct in Delaware. Longleaf Milkweed grows best in USDA hardiness zones 3-9 and reaches up to between 1 and 2.5 feet tall at maturity when in bloom.

Asclepias meadii (Mead's Milkweed)
This Midwestern native Milkweed plant is considered a threatened species and produces fragrant cream to green-colored flowers. Individual plants reach up to 1-2 feet tall when mature and in bloom, producing a single upright, unbranched stalk topped with a cluster of blooms.

Asclepias pedicellata (Savannah Milkweed, Stalked Milkweed)
These small plants produce bright yellow-green flowers, and is native to prairies and pinelands in Florida and along the southeastern coasts of the United States. Blooms pop from late spring through fall, and the plant is a larval host for Monarch, Queen, and Soldier butterflies. They reach up to 6-12 inches tall and are best when grown in USDA zones 7-10.

Asclepias perennis (White Swamp Milkweed, Aquatic Milkweed)
This species is native to eastern Texas through southern South Carolina and produces pink to cream-white flowers. These plants, unlike their genus-mates, need consistently moist soil that is rich in nutrients to perform well. They grow well in full sun to partial shade; best in USDA zones 6-10.

Asclepias prostrata (Prostrate Milkweed)
This species has leaves with wavy margins and produces light yellow flowers. These plants are native to Texas and Mexico, and are critically imperiled. Rainfall brings this species out of dormancy, and it flowers in April through October. Prostrate Milkweed grows well in USDA hardiness zones 8-10, thriving in sandy soils, warm climates and full sun.

Asclepias purpurascens (Purple Milkweed)
Flowers in this species develop from cream buds that turn red before they bloom and open to reveal magenta-pink to purple blooms. Plant this species in partial shade for best performance; they do well in USDA hardiness zones 3-9. Purple Milkweed can reach up to 2-3 feet tall and 1-3 feet wide at maturity when in bloom.

Asclepias quadrifolia (Four-Leaved Milkweed, Fourleaf Milkweed, Whorled Milkweed)
This species is at home in the eastern United States and Canada, and produces delicate white flower clusters in May through July. Whorled Milkweed reaches 1-2.5 feet tall. These plants grow well in open, rocky, dry forested areas and do well in USDA hardiness zones 4 a-8b.

Asclepias sanjuanensis (San Juan Milkweed, San Juan River Milkweed)
This species, native to the Four Corners area in northwestern New Mexico, grows well in sandy soils in mixed Juniper woodlands. produces maroon flowers and grows to just 4 inches tall at maturity, forming a prostrate plant that creeps along the ground.

Asclepias solanoa (Serpentine Milkweed, Prostrate Milkweed, Solanoa)
Native to the North Coast mountain ranges in the northern San Francisco Bay Area, this species produces heads of pink-white flowers that bloom from mauve buds. Serpentine Milkweed grows well in USDA hardiness zones 7a-10b. Stems are purple and smooth, and leaves can be ovular or heart-shaped. Individual plants reach up to a foot tall.

Asclepias speciosa (Showy Milkweed, Greek Milkweed, Pink Milkweed)
This native to western and central North America grows best in USDA hardiness zones 3-9 or Sunset growing zones 1-24, and grows to 2-4 feet tall and a little less wide. Can spread by underground stems to form colonies. Leaves are gray and soft, and summer flowers form balls of purple-pink blooms that are fragrant. Needs only occasional water once established.

Asclepias stenophylla (Slimleaf Milkweed, Narrow-Leaved Green Milkweed)
This species produces cream to light yellow flowers from June through August and is native to the Great Plains, where it is considered endangered in many states. These plants prefer gravelly, rocky soils in hilly areas. Individual plants reach up to between 8 and 40 inches tall and grow well in USDA hardiness zones 3-9.

Asclepias subulata (Rush Milkweed, Desert Milkweed)
This species is native to the southwestern United States and northern Mexico, and has cream-white flowers. Researchers in Bard, California used this species as a research subject in the search for a source of natural rubber in 1935. This species does well in USDA hardiness zones 9-11, and thrive in hot, dry, arid climates.

Asclepias subverticillata (Horsetail Milkweed, Poison Milkweed, Whorled Milkweed)
This species blooms from May through September, and is very toxic to grazing livestock and other animals, hence its common name, Poison Milkweed. It is native to New Mexico, Arizona, Colorado, Utah, and Mexico and grows well in USDA hardiness zones 5-8. Flowers are white. Plants reach up to 1 and 4 feet tall at maturity when in bloom.

Asclepias sullivantii (Prairie Milkweed, Sullivant's Milkweed, Smooth Milkweed)
This species is native to Ontario, Canada and the central United States, and produces pink to purple flowers. They typically reach up to 2-4 feet tall and half as wide. These flowers are endangered in some areas of their native range, and they normally grow in rocky, dry and disturbed soils along roadways and railways. Best in USDA zones 3-7.

Asclepias syriaca (Common Milkweed, Butterfly Flower, Silkweed, Silky Swallow-Wort, Virginia Silkweed, Broadleaf Milkweed)
This species loves sandy soils and is native to southern Canada and most of the United States east of the Rocky Mountains. Flowers are light pink to mauve and have a nice fragrance. Individual plants reach up to 3-5 feet tall and grow well in USDA zones 3-9. This species is considered invasive and aggressive outside of its native range.

Asclepias texana (Texas Milkweed, White Milkweed)
This North American native is common in Mexico and the United States (mainly Texas), growing best in USDA hardiness zones 7b-8b. Individual plants reach about 2 feet tall at maturity. Flowers are bright white, blooming in summertime.

Asclepias tuberosa (Butterfly Weed, Butterfly Milkweed, Pleurisy Root, Canada Root, Chigger Flower)
This native to the eastern United States grows best in zones 1-24 and forms a clump 3 feet tall and 1 foot wide. Clusters of bright orange flowers bloom in summer, and attract butterflies as well as birds. Varieties include those in the Gay Butterfly series (with yellow, red, orange, pink, or bicolored blossoms), and 'Hello Yellow' (with bright yellow blooms). This species is especially attractive to monarch butterflies, who lay their eggs which hatch into hungry caterpillars that feed on the leaves.

Asclepias uncialis (Wheel Milkweed, Greene's Milkweed)
This dwarf variety of Milkweed grows naturally in the southern Rocky Mountains and is considered to be endangered. Flowers are pink to purple, and bloom in spring and summertime. Individual plants reach up to between 1 and 2.5 feet tall when mature, and produce decumbent or prostrate stems. This species does well in USDA hardiness zones 6-8.

Asclepias variegata (Redring Milkweed, White Milkweed)
This species is native to eastern North America's forest openings and savannas, and grows well in USDA hardiness zones 3 through 9. Flowers are white with purplish centers and bloom in early summertime. Leaf margins are wavy and foliage is green. These plants are considered endangered in their native range, and prefer light to moderate shade.

Caring for Asclepias

Take care when planting Milkweed in the garden, as all parts are poisonous to humans and pets if ingested. Some species are also considered invasive in certain areas; check with local authorities before planting. Choose a spot in the landscape that gets full sun; ideally, these plants should be receiving between 6 and 8 hours of sun each day for best performance and flowering. They self-seed readily, so it may be prudent to locate plants in a part of the garden when they can be better controlled, such as towards the back of beds or borders, or in the corner of the landscape. Protection from wind is also a variable to consider; the less wind there is, the less seeds will be dislodged from flowering heads. The environment will also be more conducive to supporting butterflies. Milkweed plants are typically grown from seed, as they have deep taproots and do not transplant well. There are some nurseries that carry small starter specimens, however, if growing from seed is inconvenient, though keep in mind that the nursery trade commonly uses pesticides on their plants that are toxic to Monarch butterflies. These plants prefer to have their roots in fertile soil that drains well. If local soils are compacted, do not drain well, or are particularly poor in nutrients, make sure to amend the planting area with plenty of organic matter or compost before installing. Apply a thick layer of mulch around the base of plants, ensuring that mulch stays at least a few inches away from the stems. This will increase soil moisture retention, suppress weed growth, and maintain a constant soil temperature.

Fertilize Milkweed plants yearly in early springtime using organic compost, pulling back mulch before applying. Work the compost into the soil, water, and then replace mulch around the base of the plant. Asclepias do not need any additional fertilizing. Pruning Milkweed plants is relatively straightforward. Trim plants at any time during their active growing and flowering season to remove dead, damaged, or diseased foliage and spent flower inflorescences to keep the plant looking tidy. If plants are getting leggy or have too much bare stem, they can be cut back by about a third of their height to trigger a large flush of new growth. At the end of the growing season (in autumn), cut back the entire plant to about 6 inches tall and mulch over the top to protect roots for the winter. Plants can be hosts to overwintering Monarch butterfly parasites, and removing foliage lessens the chances that these parasites will cause damage to the Monarch butterfly population in the next season.

Propagation

Asclepias can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant, especially if propagating a hybrid cultivar. To propagate your Milkweed plant, follow the instructions below:

Propagating Asclepias by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
In the middle of summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 4-6 inch portion(s) of the end of a non-blooming branch and strip off all leaves except the top two pairs. The cutting should have between three and five leaf nodes. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new plant.

Propagating Asclepias by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest your seeds. The seed pods on Milkweed plants are pretty easy to spot, they're large and are left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will begin to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them. Remove all of the white fluff from seeds.
Asclepias seeds need a period of cold stratification before they can be planted. Place harvested seeds in a damp mixture of sand and potting mix in a sealable container or plastic bag, and place the container in the refrigerator for at least four weeks' time. Remove the seeds from their bed after the cold stratification period, and soak them in lukewarm water for between 12 and 24 hours. Viable seeds will sink, and any that float can be discarded, as they will not germinate.
Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 14-21 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.

Milkweed seed pods are filled with fluffy white material and papery reddish-brown seeds.

Milkweed seeds.

Problems and Pests

Take care when planting Milkweed in the landscape, as some species are considered to be invasive in certain areas due to aggressive re-seeding and spreading by rhizomes. Check with local authorities before planting. Milkweed plants can have issues with the following pests and diseases in the garden:

Powdery Mildew
Leaf Spot
Rust
Aphids

For more information on these pests and diseases, including ways to treat them, consult the following pages:

Pests & Pest Management

Plant Issues

Gallery

Milkweed plants are natural additions to all styles of landscaping, from formal to pollinator to cottage gardens.

Asclepias plants are magnets for endangered Monarch butterflies.

In this informal garden, Milkweed is planted amongst Salvia, Achillea, Silene, and Iris.

Asclepias species produce many different flower colors. The bright orange Butterfly Weed flowers stand out against the grey-green foliage and purple blooms of Liatris.