Castor bean is an evergreen herbaceous or semi-woody large shrub or small tree. This robust tender perennial can grow to 40 feet tall, developing woody stems over a few years in frost-free climates. Because of its rapid, vigorous growth, it is easily grown as a warm season annual in temperate climates, but it rarely exceeds 6-10 feet in a single growing season. This fast growing plant tends to grow straight up at first, developing branches later in the season to form a well-proportioned shrub with sturdy stems and a dense canopy. It is an excellent plant to have for vole control. A natural growing vole repellent. Note: Is poisonous to animals and humans.