Family: Crassulaceae
Origin, Description & Uses
Crassula arborescens, commonly known as silver dollar plant or tree crassula, is a succulent shrub native to South Africa. It is easily recognized by its thick, rounded, silvery-blue leaves, often edged in red, and its woody, branching form that can resemble a small tree with age. Valued for its drought tolerance and sculptural appearance, this species is widely cultivated as an ornamental in landscapes, rock gardens, and containers, particularly in dry or coastal settings. Its low water needs and ease of propagation have made it popular in home gardens and commercial plantings.
Risks & Threats
Although silver dollar plant is currently not known to be naturalized in Hawaiʻi, it possesses several traits that are cause for concern. Like many succulents, it can reproduce readily from cuttings and discarded plant material, tolerate poor soils, and thrive in dry conditions—traits that can increase the risk of escape from cultivation. If introduced into natural areas, it could potentially establish and compete with native plants, especially in dry or disturbed habitats that are already vulnerable. To help protect tropical island ecosystems, choosing a low-risk ornamental or a native plant alternative is recommended.
High Risk Traits:
- Able to grow in tropical climates
- Possibly naturalizing on Oahu, Hawaiian Islands (confirmation needed); naturalized in New Zealand
- Other Crassula species have become invasive
- Toxic to dogs, cats and potentially other animals; possibly toxic to people
- Shade-tolerant, but prefers full sun
- Forms dense populations in native range
- Reproduces by seeds and by vegetative fragments (one leaf able to form a new plant)
- Seeds dispersed by wind and intentionally by people
- Vegetative fragments can be dispersed as garden refuse
- Able to resprout after pruning or cutting
Low Risk Traits:
- Unarmed (no spines, thorns or burrs)
- Ornamental
- Possibly self-incompatible (which may limit seed production)
