# Pleurisy root (Asclepias tuberosa)

*Butterfly weed, orange milkweed, orange swallow-wort, swallow-wort, silkweed, tuber root, wind root, colic root, white root, flux root, Canada root; *Asclepias tuberosa* L.*

**Known today as.** *Asclepias tuberosa*, a handsome perennial of North America from Canada southward, most abundant in the south, one to one and a half feet high, with clusters of bright, deep orange flowers in summer; Grieve placed it in the family Asclepiadaceae. Unlike the other milkweeds it has little or none of their milky juice. The large spindle-shaped root is the drug: orange-brown outside, whitish within, with a bitterish, somewhat acrid taste. King’s traces the genus name to Aesculapius.

Kind: Plant  
Toxic: yes

> **Caution.** Grieve notes that in large doses it acts as an emetic and purgative. A 2026 case report describes a gardener, a contact-lens wearer, who suffered sudden corneal clouding and near loss of vision hours after handling the plant; the authors attribute it to its cardiac glycosides, and she improved quickly with treatment. None of the sources read for this entry reports on its safety as a medicine.

## What was it used for?

A remedy for the chest and a sweat-inducer. Grieve calls it antispasmodic, diaphoretic, expectorant, tonic, carminative, and mildly cathartic, of great use in pleurisy, “mitigating the pain and relieving the difficulty of breathing,” and in other chest complaints, diarrhoea, dysentery, and rheumatism. King’s counts it, with crawley, among the chief diaphoretics of the Eclectic materia medica, and notes that it “has a deservedly good reputation in respiratory diseases.”

## What does modern science say?

No European monograph for it was found for this entry. It was official in the United States Pharmacopoeia until shortly before Grieve wrote, and the searches of Europe PMC made for this entry found no clinical trial of it.

## Pharmacognosy and toxicology

- **asclepiadin**: a glucosidal principle, by Grieve’s account
- **cardiac glycosides**: to which a 2026 case report attributes eye injury from handling the plant

**Mechanism.** Not established in the sources read for this entry.

**Standing.** There is no European monograph. It was official in the United States Pharmacopoeia until shortly before Grieve wrote.

## What lore surrounds it?

Grieve records that “the Western Indians boil the tubers for food, prepare a crude sugar from the flowers and eat the young seed-pods, after boiling them, with buffalo meat,” and that some Canadian tribes ate the young shoots like asparagus.

## What did the older authorities say?

**Felter and Lloyd, *King’s American Dispensatory* (1898).** “Asclepias, or pleurisy root, was one of the most common of the indigenous medicines employed by the Eclectic fathers,” the book records, and its name indicated “one of its most important applications.” In 1898 the authors thought it had “fallen into unmerited neglect.” Of the plant in flower they wrote that “for miles along the railways clusters of the rich, deep orange flowers of the butterfly weed, as it is called, bedeck the fields.”

## Sources

- Grieve, M. *A Modern Herbal*, “Pleurisy Root.” As published on botanical.com.
- Felter, H. W., & Lloyd, J. U. (1898). *King’s American Dispensatory*, vol. 1, “Asclepias.” Internet Archive, kingsamericandis01kinguoft.
- Lu A, et al. (2026). Toxic Keratoconjunctivitis from Milkweed (Asclepias tuberosa) Exposure in a Contact Lens Wearer. *The Journal of emergency medicine*. PMID 41903404.
- Grieve, M. *A Modern Herbal*, “Pleurisy Root.” As published on botanical.com.
- Lu A, et al. (2026). Toxic Keratoconjunctivitis from Milkweed (Asclepias tuberosa) Exposure in a Contact Lens Wearer. *The Journal of emergency medicine*. PMID 41903404.

---

*Pleurisy root.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-10-17. The Thinking Press. https://thethinkingpress.org/materia-medica/pleurisy-root

Historical description, not medical advice.