Sword bean

While not a major commercial crop globally, sword bean holds local cultural importance in regions where it is grown. In Japan, the seeds are used to make natto—a traditional fermented bean dish—and herbal teas. In South and East Asia, the pods and seeds feature in everyday home cooking. Its role as a green manure and cover crop also ties sword bean to sustainable and organic farming traditions, underscoring its value in ecological agriculture and food security for smallholder communities.

• Sword bean’s pods can reach up to 35 cm in length, making them among the largest in the legume family.
• The plant is highly tolerant of drought and poor soils, thriving where other crops may struggle.
• Its seeds contain canavalin, a unique storage protein, and anti-nutritional factors that are rendered harmless by cooking.
• Sword bean is used not only for food but also for green manure, animal fodder, and erosion control.
• Despite its versatility, sword bean is rarely traded internationally and is mostly found in local markets.

Sword bean was domesticated in tropical Asia, with cultivation records dating back centuries in India, China, and Southeast Asia. The species was selected for its large edible pods and seeds, though the exact timeline and wild progenitor remain uncertain. Its close relationship to jack bean suggests a shared evolutionary lineage. Over time, sword bean spread to Africa, the Americas, and Oceania, primarily as a multipurpose crop for food, forage, and soil improvement. Today, local landraces dominate, with no widely recognized registered cultivars.

Sword bean is a climbing vine, grown as either a perennial or annual depending on climate and cultivation practices. In managed agriculture, it is typically grown as an annual. The plant develops thick stems, trifoliate leaves, and produces large, flat pods containing multiple seeds. Its vigorous growth enables it to cover ground quickly, suppressing weeds and protecting soil from erosion. Pod yields can reach 10–20 tons per hectare (fresh weight), with seed yields of 1–2 tons per hectare under optimal conditions.

Like other legumes, sword bean forms a symbiotic relationship with soil bacteria, enabling it to fix atmospheric nitrogen. This process enriches the soil, reducing the need for synthetic fertilizers and supporting sustainable crop rotations. When used as green manure or a cover crop, sword bean improves soil fertility, structure, and moisture retention, making it a valuable component in organic and regenerative farming systems.

Sword bean is enjoyed in various culinary forms. Immature pods are cooked as a vegetable in stir-fries, curries, and soups across South and East Asia. Mature seeds, after thorough boiling or roasting, are used in stews, ground into flour, or fermented—most notably in Japanese natto and herbal teas. Nutritionally, sword bean seeds provide protein (canavalin) and fiber, though they contain anti-nutritional factors that are neutralized by cooking. The plant’s versatility extends to livestock feed and sustainable farming practices.

Sword bean is locally significant in Asia and Africa, where it is sold in regional markets and grown by smallholders for food and forage. However, it is not a major commercial pulse in global trade, and international market presence is minimal. Regulatory bodies such as FAO and USDA do not assign specific trade codes to sword bean, often grouping it under "other pulses" or "forage legumes." Its commercial importance lies primarily in local food systems and sustainable agriculture.

Sword bean is naturally resistant to many common pests and diseases, contributing to its reliability in marginal growing conditions. However, it can be susceptible to bean fly, aphids, and fungal pathogens, particularly in humid environments. Its robust growth and tolerance to drought and poor soils make it a resilient choice for farmers seeking low-input crops, though vigilance is required in wetter climates to manage potential infestations.

Sword bean is known by a variety of names across regions and languages. Scientific synonyms include Canavalia gladiata (Jacq.) DC. and Canavalia grandiflora. Common English names are sword bean, scimitar bean, and sword-shaped bean. In Hindi, it is called Chikudukaya or Kachang parang; in Japanese, Tonasogan and Natto-mame (when used for natto); in Chinese, Dao-dou (刀豆). There are no officially registered cultivars; local landraces predominate. Sword bean is sometimes confused with jack bean (Canavalia ensiformis), but is distinguished by its larger pods and seeds.