Family: Crassulaceae
Origin, Description & Uses
Crassula multicava (Cape Province pygmyweed) is a low-growing succulent native to South Africa’s Cape Province. It forms dense mats of fleshy, bright green leaves and produces clusters of small, star-shaped pink flowers, often during the cooler months. Valued for its drought tolerance and ease of care, this species is commonly used as an ornamental groundcover, in rock gardens, and in containers. Its ability to spread quickly and thrive with minimal maintenance has made it a popular landscaping choice in warm, frost-free regions.
Risks & Threats
In Hawaiʻi, Crassula multicava is naturalized on Kauaʻi and Oʻahu and possesses traits that are cause for concern. It spreads aggressively through broken stems and plant fragments, allowing it to escape cultivation and form dense mats that can outcompete native plants for space, light, and moisture. This growth habit may suppress native understory vegetation and disrupt tropical island ecosystems. Due to its invasive potential, choosing a low-risk or native alternative is strongly recommended to help protect Hawaiʻi’s unique biodiversity.
High Risk Traits:
- Invasive: Naturalized in multiple regions (Hawaii, NZ, Australia, Europe).
- Environmental Weed: Forms dense mats that suppress native plant regeneration.
- Multiple Reproduction Modes: Spreads by seed, plantlets, and vegetative fragments.
- High Dispersal: Spread unintentionally (garden waste) and intentionally (horticulture); plantlets can become airborne.
- Wide Ecological Tolerance: Tolerant of shade and a range of soil conditions.
- Resilient: Tolerates fire/mutilation (resprouts).
Low Risk Traits:
- Harmless: Not spiny, toxic, parasitic, or allergenic.
- Palatable: Eaten by some grazing animals (e.g., Hog Deer).
- Controllable: Can be managed with herbicides.
- Non-Climbing: Low-growing, sprawling habit.
- Not an Agricultural Weed: No significant impact on crops/forestry.
