How to Grow and Care for the Red Bean Plant

The red bean plant, Vigna angularis, is the source of the adzuki bean, a small, reddish-brown legume. Cultivated for centuries in East Asia, its beans are popular in sweets and desserts due to their mildly sweet and nutty flavor. The plant is an annual that grows to a modest height, producing pods that contain the beans, making it a rewarding plant for home gardeners.

Identifying the True Red Bean Plant

Gardeners sometimes confuse the adzuki bean plant with the kidney bean plant (Phaseolus vulgaris), though they belong to different genera. Adzuki beans are small, round, and have a white ridge along one side. In contrast, kidney beans are significantly larger, kidney-shaped, and lack this ridge. Adzuki beans also have a sweeter, nuttier taste compared to the milder flavor of kidney beans.

The plants also show clear differences. The adzuki bean plant is more compact and bush-like, growing between one to two feet tall. In contrast, many kidney bean varieties can be either bush or vining pole types that require support. Adzuki pods are smooth and slender, while kidney bean pods can be larger and more varied.

How to Grow Red Bean Plants

Growing adzuki beans starts with the seeds, which are the dried beans themselves. You can use untreated, whole adzuki beans from a store. Soaking the beans in warm water for 8 to 24 hours before planting is recommended to soften the hard seed coat and improve germination rates.

Plant in the spring after all danger of frost has passed and the soil has warmed to at least 59°F (15°C). Adzuki beans require a long growing season of about 90 to 120 days to reach maturity. Plant the seeds one inch deep and four to six inches apart, with rows spaced 18 to 30 inches apart.

These plants thrive in a location that receives at least six hours of direct sunlight daily. The soil should be well-draining with a pH between 5.5 and 7.5. As a legume, this plant fixes its own nitrogen, so fertilizer requirements are minimal. Provide consistent moisture, especially during flowering and pod development, by watering the plants at their base.

The adzuki plant grows as a bush and does not need a trellis or other support. Once seedlings emerge in one to two weeks, they may need to be thinned. Thin the plants to stand about 18 inches apart to provide each one with enough space to mature and produce a good yield.

Harvesting and Processing Beans

When to harvest adzuki beans depends on your intended use. For fresh green pods, pick them when the seeds inside are just visible as outlines on the pod. For the more common dried beans, leave the pods on the plant to mature fully. Harvest when the pods turn yellowish-brown or tan and feel dry and brittle to the touch.

You can either pick the individual dry pods or cut the entire plant at its base. The plants can then be stacked in a dry, well-ventilated area to continue drying for another one to two weeks. This ensures any remaining moisture is removed. Once the pods are completely crisp, they are ready for shelling.

Shelling, or threshing, is the process of removing the beans from the pods, which can be done by hand for smaller quantities. After shelling, spread the beans on a tray in a single layer for final air drying. Properly dried beans can be stored in an airtight container in a cool, dark place for up to a year.

Common Pests and Diseases

Adzuki beans can attract several common pests.

• Aphids can be managed by introducing beneficial insects like ladybugs or by using a strong spray of water.
• The Mexican bean beetle damages leaves and can be controlled by hand-picking the beetles and their larvae.
• Adzuki pod worms can affect the crop during the growing season.
• Bean weevils are a particular concern for stored beans.

The plants are also susceptible to fungal and bacterial diseases like white mold and bacterial stem rot, especially in damp or crowded conditions. Powdery mildew may also appear on the leaves. To reduce risk, ensure good air circulation through proper spacing and water at the soil level. Rotating crops annually also helps prevent the buildup of soil-borne pathogens.

Culinary Uses for Red Beans

The most common use for adzuki beans is making sweet red bean paste, known as anko in Japan. This paste is made by boiling the beans until they are soft, then mashing and sweetening them with sugar. The smooth, rich paste is a central ingredient in many East Asian desserts, used as a filling for mochi, buns, and pastries.

Beyond paste, adzuki beans are used in other dishes. They can be boiled and added to soups or stews, cooked with rice to create the festive dish sekihan, or sprouted and added to salads for a fresh, crunchy element. Their versatility makes them a valuable addition to both sweet and savory cooking.