Kia‘i Moku: Rauvolfia vomitoria a growing problem

In Western Africa, a medicinal plant teeters on the brink of extinction. Poison devil’s pepper, or Rauvolfia vomitoria, has been overharvested by local people using the plant to treat ailments ranging from psychoses to indigestion. Some healers claim the plant’s chemicals protect the spirit of the patient against witchcraft. However, in Hawaii, R. vomitoria is responsible for an ailment of our natural areas – invading forests with amazing speed. The shrubby tree with an awful name could be at least as invasive, if not more so, than miconia.

Native to subtropical regions of Western Africa, R. vomitoria can live at elevations from sea-level to 5,000 feet. It reaches reproductive maturity within two years and, in Hawaii, flowers and produces fruit year-round. The numerous seeds are contained in an orange fruit eaten and are spread by birds. The plant grows extremely fast: Within five years a seedling will be 12-18 inches across and 30 feet tall.

Mowing or cutting doesn’t discourage this plant; a patch of R. vomitoria on Hawaii Island was 3 to 4 feet tall two months after mowing. “Ralph,” as the plant is unaffectionately called by field crews frantically working to contain this plant, has invaded gulches, pastures and waterways across 2,000 to 3,000 acres in Kohala. This superweed has spread into the mixed ohia forest at 1,600 feet elevation but could expand much farther, becoming a serious pest in agricultural and natural areas. Perhaps most disturbing is R. vomitoria’s ability to outcompete some of the most invasive plant species of tropical forests, gaining a foothold amid eucalyptus and strawberry guava despite a lack of sunlight under the canopy.

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Invasive-weed infestations within Maui County are literally a growing problem. Despite the tough economic recession, invasive species prevention and mitigation programs remain a necessity for conserving our natural and agricultural resources. We need to look back only a few months ago to remember the show of local support for our Hawaii Department of Agriculture inspectors. While some positions were retained, Maui still must deal with the losses of important HDOA positions. Despite these setbacks, our local ranchers and natural area managers remain steadfast to continue the fight against these detrimental weed infestations, simply out of necessity.