When choosing plants for year-round bloom, the best choice lies with tender, tropical varieties that bloom continuously in their native habitat. They are best planted outdoors in frost-free areas, but can be grown in containers in temperate zones. Most will continue blooming when brought indoors in areas where freezing winter temperatures are commonplace.
A popular container tree often trained as a bonsai, the calamondin orange (Citrus mitis) blooms all year long. It is not uncommon to see flowers and fruit on the plant at the same time. One of the hardiest of all citrus varieties, calamondin oranges withstand temperatures down to 20 degrees Fahrenheit. It is propagated by cuttings or grown from seeds. The seedling trees produce flowers and fruit when just two years old. Their flowers are self-fertile, requiring no cross-pollination.
Crown of Thorns
A climbing, woody, but succulent shrub, crown of thorns (Euphorbia milii) can grow up to 6 feet high. The flowers of crown of thorns are insignificant; like the poinsettia, the brightly colored bracts are the attraction. Grow crown of thorns indoors in a south-facing window during winter in cold-weather areas. Water only when the soil is dry to the touch 2 inches below the surface. The branches exude a latex-like sap when cut that may cause irritation similar to poison ivy in some individuals.
Grown as an annual in temperate areas, allamanda (Allamanda cathartica), also called golden trumpet or buttercup flower, blooms year-round when grown in tropical-like locations. It is a vine that is most often trained as a 6- to 8-foot-high shrub, although its vining growth habit makes it ideal for use in a hanging basket or as a ground cover. Its yellow, trumpet-shaped flowers grow up to 5 inches across. Grow allamanda in full sun in almost any type of soil as long as it is well drained. Allamanda withstands drought well. All parts of the plant are poisonous.