Family: Costaceae
Costus malortieanus, commonly known as stepladder ginger, spiral flag, or spiral ginger, is a tropical plant native to Central and South America. It is easily recognized by its striking, spirally arranged stems and large, lush green leaves, which give the plant a bold, architectural appearance. Showy orange to red flowers add to its ornamental appeal, making it a popular choice for tropical gardens and landscaping. Stepladder ginger is often used as an accent plant in shaded or partially shaded areas, where its unique growth form and vibrant blooms can be fully appreciated.
In Hawaiʻi, Costus malortieanus is naturalized on Maui and possesses traits that are cause for concern. It can spread beyond cultivation, forming dense patches that may outcompete native plants for light, space, and nutrients. These characteristics could detrimentally impact sensitive tropical island ecosystems, where native species often have limited ranges and few defenses against aggressive competitors. To help protect Hawaiʻi’s natural environments, choosing a low risk or native alternative is strongly recommended.
High Risk Traits:
- Thrives in tropical climates
- Naturalized on East Maui, Hawaiian Islands and Puerto Rico
- Shade-tolerant
- Forms dense stands
- Reproduces by seeds and vegetatively by rhizomes
- Seeds dispersed by birds and intentionally by people
- Able to coppice and resprout after cutting
Low Risk Traits:
- No reports of invasiveness or negative impacts reported to date
- Unarmed (no spines, thorns or burrs)
- Non-toxic
- Ornamental
- May require specialized pollinators (which may limit seed set)
