Amazonian Yam Bean

Native to the lowland tropics of South America, particularly the Amazon Basin.

• Found in the Amazonian regions of Brazil, Peru, Ecuador, Colombia, and the Guianas
• May also occur in parts of Central America
• Grows at low elevations, typically below 500 meters, in hot, humid tropical conditions
• Cultivated by indigenous peoples of the Amazon for at least 2,000 to 3,000 years
• Grows wild along river banks and in disturbed areas of the tropical rainforest
• Less widely distributed than jicama, which has spread throughout the tropics
• Genetic studies suggest all three cultivated Pachyrhizus species were domesticated independently in different regions

Amazonian Yam Bean is a vigorous, high-climbing perennial vine with very large tuberous roots.

Root:
• Very large, tuberous, irregularly shaped, typically 15 to 30 cm long and 10 to 20 cm in diameter
• Can weigh 1 to 5 kg at maturity
• Skin is brown, rough, and relatively thick
• Flesh is white, crisp, and juicy, with a sweet, slightly nutty flavor

Vine:
• Extremely vigorous climber, reaching 3 to 10 meters or more
• Stems are robust, hairy, and twining
• Leaves trifoliate with large, hairy leaflets up to 15 cm long

Flowers:
• Papilionaceous pea flowers in long axillary racemes
• White to pale violet, approximately 2 to 2.5 cm long
• Produced prolifically on mature vines

Pods:
• Large, flattened, hairy legume pods 10 to 20 cm long
• Each contains 6 to 12 seeds
• Seeds, pods, leaves, and stems are TOXIC (contain rotenone)

Amazonian Yam Bean provides good nutrition as a starchy yet refreshing root crop.

• Per 100 g raw root: approximately 40 to 55 kcal
• Moderate carbohydrate content with significant dietary fiber
• Provides vitamin C and small amounts of B vitamins
• Contains potassium, calcium, and iron
• High water content (80 to 88%) for hydration
• Contains inulin-type fructans that act as prebiotics
• Low fat and low protein content
• Provides some phosphorus and magnesium
• The fiber content helps regulate blood sugar

As with all Pachyrhizus species, only the tuberous root is edible. All above-ground parts contain rotenone and are toxic.

• Seeds have the highest concentration of rotenone
• Leaves and stems also contain significant toxin levels
• Pods are poisonous
• Traditional Amazonian peoples used crushed seeds as a fish poison (barbasco) for fishing
• The root is safe to eat raw or cooked

Amazonian Yam Bean is traditionally cultivated in shifting agriculture systems in the Amazon.

Planting:
• Sow seeds at the beginning of the rainy season in tropical lowlands
• Plant 2 to 3 cm deep, spaced 30 to 50 cm apart at the base of supports or trellises
• Requires 7 to 12 months to produce mature roots

Growing:
• Requires hot, humid tropical conditions with abundant rainfall
• Thrives in rich, well-drained alluvial soils near rivers
• Extremely vigorous vine that needs strong support — can climb 10+ meters into canopy
• Tolerant of flooding and waterlogged conditions better than other Pachyrhizus species
• Flower removal may increase root yield
• Nitrogen-fixing via rhizobial symbiosis

Harvest:
• Harvest when vines begin to senesce, typically 8 to 12 months after planting
• Dig carefully around the base of the plant to extract the large roots
• Can be harvested progressively as needed in home gardens
• Roots store reasonably well in cool, dry conditions for several weeks

Amazonian Yam Bean is eaten primarily raw or lightly cooked in Amazonian communities.

Culinary Uses:
• Eaten raw: peeled and sliced as a refreshing snack
• Grated or cubed in salads
• Boiled or roasted as a starchy side dish
• Sometimes fermented in traditional Amazonian food preparation
• Added to soups and fish stews in indigenous communities

Other Uses:
• Seeds used as fish poison (barbasco) by indigenous peoples — a traditional fishing method
• The vigorous vine provides ground cover and erosion control
• Nitrogen fixation improves soil for subsequent crops
• Has potential as an underutilized tropical root crop for food security
• Studied for potential commercial development in humid tropical regions