Rauvolfia vomitoria, commonly known as Ralf or swizzle stick, is a fast-growing invasive tree. Native to the subtropical regions of Western Africa, R. vomitoria was imported to Hawaiʻi around 1957. Plantings occurred in the Kohala region of Hawaiʻi Island with the hope of producing medicinal compounds. It has spread from the initial plantings into the forest of that area.
It reaches reproductive maturity in two years, is shade tolerant, and it grows back vigorously after cutting. To make matters worse, it produces fruit all year long, which are bird-dispersed. The Kohala invasion is at least 2 to 3 thousand acres, some in pristine native forest. There are cultivated trees in Oahu at Ho’omaluhia Botanical Garden; some evidence suggests that the tree is spreading into the closed-canopy forest. It has the potential to be a serious agricultural pest as cattle don’t eat it. Ralf is spreading into pasture lands at the same time, degrading the forage cattle depend on for food.
Description and Dispersal:
- A small tree or shrub up to 30 ft tall, with a trunk 1 ft in diameter
- Long skinny leaves (up to 9.5 in long) with pointy tips grow in a whorled pattern in groups of 3-5
- Minute cream colored flowers (less than 1/10 in) grow in clusters and are sweet smelling; clustered red-orange fruits (1/3 in diameter)
- Seeds dispersed long distances by birds, produces fruit year-round