Rosary pea (Abrus precatorius) is a common exotic vine in South Florida (including Sanibel) that is native to tropical Asia. It escaped from the plant trade in the 1930s in the United States. It has since become pantropical, which means it is now found around the world in tropical and semitropical areas.
This plant is easily identified by pairs of alternate leaves on a petiole, which is a stalk that attaches the leaves to the plant’s stem and can twist leaves to face the sun. Its highly toxic seeds are bright red with a black base. The seeds superficially resemble a ladybug and are attached to a brown seed case that splits open, dropping seeds to the ground.
One ingested seed (legume) by humans and wildlife can be fatal if not treated. The toxin abrin, which is found in the seeds, is one of the deadliest toxins to human beings found in the plant world. However, birds eat them with no ill effects and spread the seeds around in their feces. At this time of year, the seeds are highly visible and are falling off the plant. Their beauty and consistent size and shape have made them suitable for jewelry (including rosaries) in their native range. After being boiled to denature the toxin, the seeds are also used in traditional medicines.
Rosary pea is often found remarkably high up in trees as the vine wraps and grows its way upward. They can be difficult to eradicate due to their deep root system. SCCF Wildlife & Habitat Director Chris Lechowicz says that pulling them out of the ground, especially young plants, can be effective “but diligence is needed to keep them under control,” he advises. Herbicides can be used for mature plants but repeat treatments may be needed due to regrowth.