Tropical Milkweed
Asclepias curassavica L.
The scarlet-and-gold milkweed sold in nearly every garden center. It is not native to the United States, it flowers relentlessly, and in frost-free regions that is exactly the problem: it disrupts monarch migration and builds up parasite loads. Beautiful plant, genuinely bad ecological actor south of the frost line.
Also called Bloodflower, Mexican Butterfly Weed, Scarlet Milkweed.
- Height
- 2 ft–4 ft
- Spread
- 1.5 ft–2.5 ft
- Flowers
- red, orange, yellow
- Bloom
- nearly year-round in frost-free areas
- Light
- Full sun, Part shade
- Soil moisture
- Average
- USDA zones
- 8–11
- Leaves
- Opposite, lanceolate
- Sap
- Milky latex
- Roots
- Fibrous, clump-forming and easy to move
- Stratification
- None needed
- Range
- 11 states
When it flowers
Tropical Milkweed blooms nearly year-round in frost-free areas, peaking in June and July and August and September.
How to identify it
- Flowers are two-toned, a red or orange corolla with a bright yellow-orange crown, unlike any native species.
- Blooms continuously rather than in a defined season.
- Smooth, dark green lance-shaped leaves; slender upright stems; no basal woodiness in the first year.
- Pods are narrow, smooth and upright.
Ecology and wildlife value
Monarchs will lay on it eagerly, but in the Gulf states, California and Florida it stays green all winter and encourages butterflies to break their migration and breed year-round. Those resident populations accumulate the protozoan parasite Ophryocystis elektroscirrha (OE), which shortens lifespans and deforms wings. Studies also show that cardenolide levels rise under heat, which may harm larvae.
Growing tropical milkweed
Grown as an annual north of zone 8 it is harmless and useful. It germinates without stratification, blooms in twelve weeks from seed and dies at the first frost. In zones 9 to 11, either cut it to the ground each October through February or, better, replace it with a native species.
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
Several US counties and native plant societies now discourage or restrict its sale. If you garden in Florida, the Gulf Coast, southern California, Arizona or Hawaii, please choose a native milkweed instead. More on milkweed toxicity.
Where tropical milkweed grows
Recorded in 11 states: Alabama, Arizona, California, Florida, Georgia, Hawaii, Louisiana, Mississippi, North Carolina, South Carolina, Texas.
Distribution is generalized to state level. For county-level maps see USDA PLANTS and BONAP.
Frequently asked questions
Is tropical milkweed bad for monarchs?
In frost-free regions, yes. Because it does not die back it supports winter breeding, which raises OE parasite infection rates dramatically and can interrupt migration. In cold-winter regions where frost kills it each year, the evidence of harm is much weaker.
Should I cut back my tropical milkweed?
If you are in zone 9 or warmer, cut every plant to within six inches of the ground in October and keep it cut through February. That mimics the natural winter dieback and reduces parasite build-up.
What should I plant instead of tropical milkweed?
Match your region: swamp milkweed and butterfly weed almost anywhere, aquatic milkweed or pinewoods milkweed in Florida, zizotes and antelope horns in Texas, narrowleaf milkweed in California.
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 94213-1. Royal Botanic Gardens, Kew. Accepted name, authorship and global distribution.
- GBIF 3170241. Global Biodiversity Information Facility. Aggregated occurrence records.
- iNaturalist 75602. Community observations, photographs and phenology.
- Wikipedia. General-audience article on this species.
- BONAP county distribution map. Biota of North America Program. County-level range map.
- 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
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Milkweed USA. (2026). Tropical Milkweed (Asclepias curassavica). Retrieved DATE, from https://milkweedusa.com/species/tropical-milkweed/
"Tropical Milkweed (Asclepias curassavica)." Milkweed USA, 2026, https://milkweedusa.com/species/tropical-milkweed/. Accessed DATE.
Milkweed USA. "Tropical Milkweed (Asclepias curassavica)." Last modified 2026-08-01. Accessed DATE. https://milkweedusa.com/species/tropical-milkweed/.
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title = {Tropical Milkweed (Asclepias curassavica)},
author = {{Milkweed USA}},
year = {2026},
url = {https://milkweedusa.com/species/tropical-milkweed/},
note = {Accessed DATE}
}