Plant · P-246

Jack Bean

Canavalia ensiformis

Jack bean is a green manure and cover crop first, and only a marginal food plant - the whole plant carries a lectin and an arginine-blocking compound that make it genuinely dangerous raw. It tolerates almost anything a site can throw at it: waterlogging, salinity, drought on a deep root system, and alkaline ground, a combination almost no other legume here can match. Ploughed in at flowering, when nodulation also peaks, it is credited with fixing as much nitrogen as any legume in this group. Raw seed can kill cattle outright, so it belongs in cropped beds and fenced orchard alleys, cut and turned as green manure, rather than anywhere livestock or poultry can reach it.