Do Hyacinth Bean Plants Come Back Every Year?

Growth Characteristics

• Once soil temperatures reach at least 65 degrees Fahrenheit, hyacinth bean seeds germinate in well-drained, fertile garden soil. Tropical weather, with air temperatures above 85 F, leads to fast growth, with the plant reaching 10 to 20 feet long in one frost-free growing season. Flowering occurs in the summer heat, too, and continues well into the fall. In winter, hyacinth bean stops flowering in the tropical winter dry season and some leaves and stems naturally die back from the drier soil conditions. Once spring returns, growth and flowering resume as it warms up.

Plant Longevity

• Frost kills back hyacinth beans to its roots. Prolonged subfreezing temperatures penetrate into the soil to also kill the roots. In USDA zone 9, frosts kill the foliage and stems, but plants may rejuvenate in spring if the roots weren't frozen. In colder regions, the plants die each winter. Any seed pods that drop to the ground may sprout the following spring, giving an illusion the hyacinth bean is perennial even in cold winter regions. In tropical regions, the hyacinth bean remains nearly evergreen over winter. Gardeners prune it back to 1 or 2 feet tall in late winter to encourage lush new growth.

Seeds

• In some parts of the U.S., such as in Hawaii, Puerto Rico or southern Florida, hyacinth bean endures as a perennial and sets seeds that also sprout in the garden. In these regions the plant may be regarded as a pesky weed. In colder regions farther north, gardeners need to let some seed pods develop and ripen in late summer or early fall. Collect the seed pods and remove the dark purple-brown or black seeds to store over winter. Plant the seeds next spring to enjoy new plants year after year.

Flowering and Seed Production Tip

• To encourage more flowers and subsequent seed pod production, water and fertilize a hyacinth bean vine during the heat of late spring and summer, from May to early September. Keep the soil evenly moist, supplementing rainfall as necessary. Fertilize the young, growing vine every 10 to 14 days. Use a balanced formulation of liquid fertilizer, following product directions for dosage and application. Reduce frequency of fertilization once flowers form on the vine's twining stem tips.