Fast-growing and ornate in both foliage and flower, hyacinth bean (Lablab purpureus) is a native of tropical Africa where it's also eaten as a vegetable crop. The three-part leaves are medium green, often with a purplish cast and densely cover the vine that will reach heights of 10 to 20 feet. The flowers are sweet pea-like and violet and white, held above the foliage. Attractive dark purple seed pods occur thereafter.
Found in scrubland, hyacinth bean is native to the tropical areas in sub-Saharan Africa. It has become extensively cultivated in northern Africa and Asia as a food crop.
A perennial vine, it has fast-growing, twining stems that will readily clasp and climb upon any vertical support to heights of 10 to 20 feet, depending on length of growing season. Without support, it will clamber its stems across the ground and raise its flower clusters upright from the carpet of leaves.
Hyacinth bean's foliage ranges in color from medium to deep green, sometimes with a hint of purple casting on the green. Each leaf is trifoliate, meaning it is made up of three leaflets. The leaflets are oval to triangular in shape. The foliage is edible.
Flowers and Seeds
In the abundant warmth of summer and autumn, hyacinth bean bears loose clusters of fragrant flowers from stem tips above the mass of leaves. The blossom looks like those of a sweet pea, colored pinkish violet to bi-colored white and purple, attracting bees for pollination. The fertilized ovary of the flower matures into a flat, dark purple-burgundy seedpod that is both decorative and edible, as long as the seeds are immature. Ripe seeds, which are brown to black, should not be eaten as they are laced with toxins.
Sow seeds of hyacinth bean in a fertile, moist, well-draining soil in as much sunlight as possible to promote abundant flowering. While temperatures are above 75 degrees Fahrenheit in the growing season, water and fertilize frequently. Frost will kill the plant to the roots, and subfreezing temperatures will kill the entire plant.
Hyacinth bean is often grown as an annual. However, in tropical climates, those with a USDA Hardiness Zone rating of 10 and higher, it will become a short-lived perennial vine that may be pruned back hard to 12 to 24 inches in early spring and allowed to rejuvenate.
Provide a sturdy support trellis, fence or arbor upon which the vining stems may grow.
Harvest the seedpods in autumn so you have fresh seeds to sow next spring.
Japanese beetles will devour the foliage of hyacinth bean but it will rejuvenate quickly and flower in the latter half of the growing season up until frost.