Family: Asteraceae
Cosmos sulphureus (orange cosmos, sulphur cosmos) is a fast-growing annual flowering plant native to Mexico and Central America. It is best known for its bright orange to yellow daisy-like flowers, finely divided foliage, and long blooming season. Orange cosmos is widely used in gardens, roadsides, and restoration seed mixes because it is easy to grow, tolerant of poor soils, and attractive to pollinators such as butterflies and bees. Its showy flowers and low maintenance needs have made it a popular ornamental in Hawaiʻi, where it is commonly planted for color and erosion control.
Although Cosmos sulphureus is not currently known to be fully naturalized in Hawaiʻi, it is potentially naturalizing on Oʻahu and Maui and possesses several traits that raise concern. This species produces abundant seeds, grows rapidly, and readily establishes in disturbed areas, allowing it to spread beyond cultivation. In tropical island ecosystems, these characteristics can enable it to outcompete native plants, alter plant communities, and reduce habitat quality over time. To help protect Hawaiʻi’s unique ecosystems, it is recommended to choose a low-risk or native alternative that provides similar visual appeal without the potential ecological impacts.
High Risk Traits:
- Thrives in tropical climates
- Broad climate suitability
- Widely naturalized
- A garden and disturbance weed
- Other Cosmos species have become invasive
- Unpalatable to deer
- Tolerates many soil types
- Seeds freely
- Self-compatible
- Annual able to reach maturity in one growing season
- Seeds dispersed intentionally by people and externally on animals and possibly machinery or clothing
Low Risk Traits:
- Unarmed (no spines, thorns or burrs)
- Requires full sun
- Not known to spread vegetatively
- Used as an ornamental and to attract and benefit pollinators
