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A Comprehensive Guide to Woollypod Milkweed (Asclepias eriocarpa)

Woollypod Milkweed (Asclepias eriocarpa) is a herbaceous perennial that is found in the state of California. This plant is a host to the Monarch (Danaus plexippus), Queen (Danaus gilippus) and Soldier (Danaus eresimus) butterflies. It can grow to 3 feet tall and has green, white to pink flowers that bloom from April to October. It is hardy in zones 4-9.

Taxonomy and Naming of Woollypod Milkweed (Asclepias eriocarpa)

Herbarium specimen of woollypod milkweed (Asclepias eriocarpa).
Herbarium Specimen — Asclepias eriocarpa Benth. collected in United States of America by The New York Botanical Garden (licensed under CC BY 4.0)
Holotype specimen of woollypod milkweed (Asclepias eriocarpa).
Holotype Specimen — Asclepias fremontii Torr. collected in United States of America by The New York Botanical Garden (licensed under CC BY 4.0)


Woollypod milkweed (Asclepias eriocarpa) was named and described by George Bentham, an English botanist, in 1840. It has kept this name since being described and named. This plant is a member of the Dogbane Family (Apocynaceae).


  • Asclepias fremontii
  • Asclepias eriocarpa var. microcarpa

Meaning of the Scientific Names and Common Names

Scientific Name

The genus name, Asclepias, is named for the Greek god of healing, Asklepios (Flora of Wisconsin). The species name, eriocarpa, comes from the Greek word “erion” for wool and “carpos” for fruit (Friends of Queens Park Bushland). It apparently describes the fruit once it spilts apart.

Common Name and Alternative Names

The common name likely comes from the same idea as the latin species name and describes the fruit. Other names include Indian milkweed and kotolo.

Physical Description

Vegetative plant of woollypod milkweed (Asclepias eriocarpa).
Plant of Woollypod Milkweed — Pacific Southwest Region USFWS from Sacramento, US, Public domain, via Wikimedia Commons
  • Plant Type: This plant is a herbaceous perennial.
  • Height: 2 to 4 feet
  • Stem: tomentose
  • Leaves: The leaves are opposite to whorled in 3s or 4s, simple, entire rippled margined, and lanceolate to oval in shape. They have been described as mullein-like and the upper leaves may be alternate (Marsh and Clawson 1924). They range in size from 4 to 8 inches in length and 1 to 3 inches in width. The leaves can have a fuzzy appearance and be a lighter green underneath.
  • Flower color: The flowers are greenish to yellowish-white and may be tinged with rose (Woodson 1954) or pink (Calscape). The flowers give off a wax fragrance (
  • Blooming period: This plant blooms from May to October.
  • Fruiting type and period: This plant has follicles that mature in the late summer and fall.

Range of Woollypod Milkweed (Asclepias eriocarpa) in the United States

Range map of woollypod milkweed (Asclepias eriocarpa) in the United States and Canada.
Kartesz, J.T., The Biota of North America Program (BONAP). 2015. North American Plant Atlas. ( Chapel Hill, N.C. [maps generated from Kartesz, J.T. 2015. Floristic Synthesis of North America, Version 1.0. Biota of North America Program (BONAP). (in press)].

This species is found in the state of California in the United States and Canada. The range of the species extends south into Mexico along the Baja Peninsula.


Dry rocky woodland habitat.
Dry Woodland Habitat — Patrick Alexander from Las Cruces, NM, CC0 1.0
, via Wikimedia Commons

This species grows on rocky hillsides, deserts, open woods, fields, roadsides, and other dry areas.

Hosted Insects

Monarch butterfly on green flower.
Green Flower with Monarch Butterfly — U.S. Fish and Wildlife Service, Public domain, via Wikimedia Commons

This species is a host for the Monarch Butterfly (Danaus plexippus), the Queen Butterfly (Danaus gilippus) and the Soldier Butterfly (Danaus eresimus).

Other Supported Wildlife

Wood thrush on branch.
Wood Thrush — Andy Reago & Chrissy McClarren, CC BY 2.0, via Wikimedia Commons

This species produces abundant nectar and is used by other butterflies, bees, and milkweed beetles (Root 1986) and birds in the late summer and fall.

Frequently Asked Questions

Is this plant poisonous?

Like other milkweeds, it has cardiac glycosides (cardenolides) and is considered to be poisonous with ingestion. It is considered among the most poisonous of the milkweeds ( is poisonous to pets such as cats and dogs.

Does this plant have any ethnobotanical uses?

The Native American Ethobotanical Database shows that this plant has been used for drugs, food, fiber, and for hunting and fishing.

How is this plant distinguished from others?

This milkweed is distinguished by the silvery colored foliage.

Is this plant deer resistant?

According to Calscape, this plant is deer resistant.

Gardening with Woollypod Milkweed

Add Woollypod Milkweed to Your Garden

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Close-up of pinkish-white flowers of woollypod milkweed (Asclepias eriocarpa).
Flowers of Woollypod Milkweed — Anthony Valois, Public domain, via Wikimedia Commons


This species is hardy in zones 4-9. If your garden is within these zones and you have the right growing conditions (soil and moisture), you may well be able to grow this plant.

Optimal Conditions

This species can handle full sun to partial shade and mesic to dry well-drained soil with a neutral pH.


  • Marsh, C. Dwight and A.B. Clawson. 1924. The woolly-pod milkweed (Asclepias eriocarpa) as a poisonous plant. USDA Department Bulletin No. 1212.
  • Root, R.B. 1986. The life of a californian population of the facultative milkweed bug, Lygaeus kalmii (Heteroptera: Lygaeidae). Proc. of the Entomological Society of Washington 88: 201-214.
  • Woodson, Robert E. 1954. The North American Species of Asclepias L. Annals of the Missouri Botanical Garden 41: 1-211.
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Robert Coxe

Robert Coxe

Robert Coxe is a professional ecologist and botanist who has worked as the State Ecologist of Delaware and as an ecologist for the Western Pennsylvania Conservancy. He is also a former Past-President of the Pennsylvania Academy of Science. He currently is an innkeeper at McMullen House Bed & Breakfast LLC and a web designer and owner for Silphium Design LLC.

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