India, Oct. 20 -- Some plants look like a great idea until they take over the yard. Hawaii learned that lesson on a huge scale with gorse, a thorny shrub from western Europe. A 2000 Hawaii Department of Agriculture news release said gorse was introduced to Hawaii from England or Scotland in the early 1900s for sheep forage. By then, more than 35,000 acres on Maui and the Big Island were covered by the weed. That's how a useful plant became a chronic problem for the islands.

People once valued gorse for practical reasons. A 1988 paper by George Markin and colleagues, published in the Hawaiian Botanical Society Newsletter, states that it was considered an effective hedgerow plant until barbed wire started being used for fences. The authors...