Family: Orchidaceae
Origin, Description & Uses
Polystachya concreta, commonly known as great yellow spike orchid or yellow spike orchid, is native to Tropical and Subtropical America. It is a small epiphytic orchid that grows on tree trunks and branches in warm, humid forests. The plant produces slender, upright flowering spikes with many small yellow-green flowers, giving it a delicate, airy appearance. In cultivation, it is sometimes used as an ornamental orchid, valued for its unique form and ability to grow mounted on trees or in shaded garden settings that mimic its natural habitat.
Risks & Threats
In Hawaiʻi, this orchid is naturalized on Kauaʻi, Oʻahu, Molokaʻi, and Maui. It is currently considered low risk because it does not form dense infestations or aggressively compete with native plants. While it can spread locally through wind-dispersed seeds, it generally integrates into forest canopies without significantly altering native ecosystems. At present, it is not known to pose major ecological or economic threats, though continued monitoring is useful to ensure it remains well-behaved in Hawaiian habitats.
High Risk Traits:
- Elevation range exceeds 1000 m, demonstrating environmental versatility
- Thrives in tropical climates
- Naturalized on Oahu, Molokai, and Maui (Hawaiian Islands)
- Establishes in native forest; could potentially compete with native epiphytes
- Shade-tolerant
- Reproduces by seeds
- Self-compatible
- Seeds dispersed by wind and intentionally by people
- Prolific seed production
- Gaps in biological and ecological information may limit accuracy or risk prediction
Low Risk Traits:
- Despite naturalization, no reports of negative impacts to date
- Unarmed (no spines, thorns, or burrs)
- Ornamental
- Requires specialized pollinators (although fruit production apparently not limiting factor in Hawaiian Islands)
