The asparagus bean, also known as the yardlong bean or long bean, is a popular vegetable characterized by its long, slender pods, which typically range from 35 to 75 centimeters (1.15 to 2.46 feet) in length. This vigorous climbing annual vine originated in the warmer regions of South Asia, Southeast Asia, and southern China, where it is widely cultivated.
Distinguishing the Asparagus Bean
Despite its common name, the asparagus bean is not botanically related to true asparagus (Asparagus officinalis). It belongs to the legume family (Fabaceae) as a subspecies of cowpea (Vigna unguiculata subsp. sesquipedalis), while true asparagus is in the Asparagaceae family. The “asparagus” moniker likely comes from its slender appearance or subtle flavor notes when cooked. This vining bean is distinct from common beans and is grown for its immature, edible green pods.
Cultivating Asparagus Beans
Asparagus beans thrive in warm climates, requiring at least 75 frost-free days to mature. They prefer full sun and well-drained, loamy soil. While not demanding exceptionally rich soil, incorporating compost during planting improves growth.
Direct sow seeds after the last frost, when soil temperatures reach at least 10°C (50°F). Plant seeds about 2.5 cm (1 inch) deep and 5 to 10 cm (2 to 4 inches) apart.
As climbing vines, asparagus beans need sturdy support like trellises, stakes, or fences, which should be in place at planting to accommodate their 2.4 to 3.7 meter (8 to 12 feet) height.
Consistent moisture is beneficial, though they exhibit some drought resistance. Harvesting begins 60 to 85 days after sowing, when pods are tender and 30 to 45 cm (12 to 18 inches) long. Regular harvesting every one to two days promotes continuous production and prevents pods from becoming tough.
Culinary Uses and Nutritional Value
Asparagus beans are prized in various cuisines, particularly Asian cooking, for their mild, nutty flavor and crisp-tender texture. They are versatile and can be stir-fried, steamed, boiled, roasted, or eaten raw in salads. In the Philippines, they are often stir-fried with soy sauce, garlic, and hot pepper, or stewed in dishes like pinakbet.
Asparagus beans also offer a strong nutritional profile. A 100-gram serving contains approximately 47 calories, 2.8 grams of protein, and 8.35 grams of net carbohydrates. They are a good source of dietary fiber, supporting digestive health, and provide various vitamins and minerals, including Vitamin C (about 19 mg), Vitamin A (around 865 IU), iron, phosphorus, potassium, magnesium, and manganese.