Balloon Plant
Gomphocarpus physocarpus E. Mey.
Not a true milkweed but a close African relative, grown everywhere for its extraordinary inflated, bristly, balloon-like pods. Monarchs will use it as a host, and in frost-free regions it raises exactly the same winter-breeding concerns as tropical milkweed.
Also called Hairy Balls, Swan Plant, Balloon Cotton Bush.
- Height
- 3 ft–6 ft
- Spread
- 2 ft–4 ft
- Flowers
- white, cream
- Bloom
- May to October
- Light
- Full sun
- Soil moisture
- Average
- USDA zones
- 8–11
- Leaves
- Opposite, narrow
- Sap
- Milky latex
- Roots
- Fibrous, clump-forming and easy to move
- Stratification
- None needed
- Range
- 9 states
When it flowers
Balloon Plant blooms May to October, peaking in July and August.
How to identify it
- Pods are pale green spheres covered in soft bristles, unmistakable and unlike any Asclepias.
- Small waxy white flowers hanging in nodding clusters.
- Tall, shrubby, softly hairy stems with narrow willow-like leaves.
Unfamiliar words are in the glossary, and the identification key will narrow a plant down from what you can see.
The parts that identify it
Ecology and wildlife value
Monarch larvae develop successfully on it, and it is widely used in butterfly houses and school rearing projects. It is native to southern Africa, not North America.
Monarchs are not the only thing that will find it. Expect large milkweed bugs on ripening pods, oleander aphids on the stems, red milkweed beetles at the flowers and, in late summer, milkweed tussock moths. Everything that lives on milkweed.
Growing balloon plant
Easy from seed with no stratification and fast enough to flower in one season, so it is best grown as an annual in cold regions. In zones 9 and warmer, cut it back through winter or use a native species instead.
Seed needs no cold stratification and can be sown fresh. Fibrous, clump-forming and easy to move. See how to plant milkweed seed for the full method.
Cautions
Non-native. In frost-free regions its evergreen growth encourages winter monarch breeding and OE parasite build-up, exactly as tropical milkweed does. More on milkweed toxicity.
Where balloon plant grows
Recorded in 9 states: Alabama, California, Florida, Georgia, Hawaii, Louisiana, Mississippi, South Carolina, Texas.
USDA PLANTS holds no county-level records for this species, so the map above is generalized to whole states. For what county data exists see USDA PLANTS and BONAP.
Frequently asked questions
Is balloon plant the same as milkweed?
It is a close relative in the same subfamily, not a true Asclepias. Monarch caterpillars do eat it, but it is native to southern Africa. In frost-free regions the same winter-breeding cautions apply as for tropical milkweed.
References and further reading
Names, ranges and conservation status here are drawn from the databases below. Where those disagree with a regional flora, trust the flora.
- Plants of the World Online 97670-1. Royal Botanic Gardens, Kew. Accepted name, authorship and global distribution.
- GBIF 3170326. Global Biodiversity Information Facility. Aggregated occurrence records.
- iNaturalist 281273. Community observations, photographs and phenology.
- Wikipedia. General-audience article on this species.
- NatureServe Explorer. Conservation status ranks at global and state level.
- World Flora Online. Nomenclature and synonymy.
- Woodson, R. E. (1954). The North American species of Asclepias L.. Annals of the Missouri Botanical Garden 41(1): 1–211. The monograph the modern taxonomy of the genus still rests on. View
- Flora of North America Editorial Committee (eds.) (2026). Flora of North America North of Mexico. Oxford University Press, New York and Oxford. Accepted names, keys and descriptions for the North American flora. View
- Royal Botanic Gardens, Kew (2026). Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. Nomenclature and global distribution, keyed to IPNI name identifiers. View
- Kartesz, J. T. (Biota of North America Program) (2026). North American Plant Atlas. BONAP, Chapel Hill, North Carolina. County-level distribution maps, the basis for the ranges generalized here. View
- USDA, NRCS (2026). The PLANTS Database. National Plant Data Team, Greensboro, North Carolina. State-level distribution, wetland status and nomenclature. View
- Agrawal, A. A. (2017). Monarchs and Milkweed: A Migrating Butterfly, a Poisonous Plant, and Their Remarkable Story of Coevolution. Princeton University Press. The standard general account of the milkweed and monarch relationship. View
Cite this page
This page is licensed CC BY 4.0. Quote it, adapt it and reuse it, including commercially, as long as you credit Milkweed USA and link back.
Milkweed USA. (2026). Balloon Plant (Gomphocarpus physocarpus). Retrieved DATE, from https://milkweedusa.com/species/balloon-plant/
"Balloon Plant (Gomphocarpus physocarpus)." Milkweed USA, 2026, https://milkweedusa.com/species/balloon-plant/. Accessed DATE.
Milkweed USA. "Balloon Plant (Gomphocarpus physocarpus)." Last modified 2026-08-01. Accessed DATE. https://milkweedusa.com/species/balloon-plant/.
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title = {Balloon Plant (Gomphocarpus physocarpus)},
author = {{Milkweed USA}},
year = {2026},
url = {https://milkweedusa.com/species/balloon-plant/},
note = {Accessed DATE}
}