How to Grow Perennial Soybean
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Perennial Soybean
Neonotonia wightii
vinePerennial Soybean is a vigorous, nitrogen-fixing legume native to Africa that grows as a trailing or climbing vine. It produces small purple flowers followed by hairy pods containing seeds used as a protein-rich forage crop and soil amendment. This plant is valued in tropical and subtropical agriculture for soil improvement, livestock feed, and erosion control.
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Example Perennial Soybean timeline · Pittsburgh, PA (Zone 6b)
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Plant Perennial Soybean
Around Apr 17Near Pittsburgh's average last spring frost.
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Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
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Harvest Perennial Soybean
Around Jul 16≈ 90 days after planting
Sample dates for Pittsburgh, PA. Sign up to get exact Perennial Soybean dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in USDA zones 9b-11, frost-sensitive but persists as perennial in warm climates
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Germination & Seedling
3-4 weeksSeeds germinate in 7-14 days. Seedlings develop compound trifoliate leaves and a taproot system.
Maintain soil moisture without waterlogging. Protect from direct intense heat during first 2-3 weeks. Thin to proper spacing early.
Vegetative Growth
6-8 weeksPlant develops vigorous trailing or climbing vines with abundant compound leaves. Root nodulation establishes nitrogen-fixing capacity.
Provide support structure (trellis, stakes) if desired. Allow adequate spacing for air circulation. Monitor for early pest establishment. The plant fixes its own nitrogen, reducing fertilizer needs.
Flowering
4-6 weeksSmall purple to violet flowers appear in axillary clusters along the vines. Flowering indicates reproductive maturity.
Maintain consistent moisture during flowering for better pod set. Reduce nitrogen fertilizer if applied, as it may promote vegetative growth over reproduction.
Pod Development & Seed Maturation
6-8 weeksSmall hairy seed pods develop and mature. Each pod contains 2-4 seeds. Pods turn brown and dry as seeds mature.
Reduce watering as pods mature to encourage seed development. Protect from excessive rain if seeds will be harvested. Watch for pod-feeding insects.
Harvest & Regrowth
Ongoing in perennial cultivationSeeds are ready for harvest; pods shatter easily when dry. Plant can be cut back for regrowth or allowed to reseed.
Harvest before pods shatter naturally. Dry seeds thoroughly before storage. Cut stems 4-6 inches from ground for regrowth in following season.
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Destroy infested seedlings; plant resistant varieties; practice crop rotation; apply neem oil to young plants
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Store dried seeds with diatomaceous earth or neem powder; maintain cool, dry storage; use hermetic containers
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Increase humidity through irrigation; spray undersides of leaves with water; apply insecticidal soap; use predatory mites in severe cases
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Monitor regularly; hand-pick if populations are low; apply Bacillus thuringiensis (Bt); use neem oil for heavy infestations
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Rotate crops; solarize soil; add resistant cover crops; avoid infested fields
Uses
Livestock Forage & Feed
CulinaryPerennial soybean is widely used as a nutritious fodder crop for cattle, goats, sheep, and poultry. The protein-rich leaves and pods provide high-quality animal feed both fresh and dried as hay. [source]
Soil Nitrogen Enrichment
HouseholdAs a nitrogen-fixing legume, Neonotonia wightii improves soil fertility through symbiotic relationships with rhizobia bacteria. The plant is used as a green manure or cover crop to naturally increase nitrogen availability for subsequent crops. [source]
Erosion Control & Land Reclamation
HouseholdThe vigorous vine growth and extensive root system make this plant effective for preventing soil erosion on slopes and degraded lands. It stabilizes soil while adding organic matter. [source]
Human Food Source
CulinaryIn some regions, the young pods and seeds are consumed as a vegetable or pulse by local populations. The seeds can be cooked like beans and provide substantial protein. [source]
Traditional Medicine
MedicinalIn African traditional medicine, various parts of the plant have been used to treat digestive ailments and provide nutritional support. The plant is rich in minerals and phytochemicals. [source]
This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.
Harvest Tips
Harvest pods when brown and dry, typically 5-6 months after planting. Pick pods before they shatter naturally to collect seeds. Dry harvested pods further in sun for 1-2 weeks, then thresh to extract seeds. Store dried seeds in cool, dry conditions with low humidity to prevent weevil infestation. For forage use, cut plants during active growth period and allow to dry for hay or silage.
Fun Facts
- 🌱 Perennial soybean's scientific name, Neonotonia wightii, honors botanist Robert Wight, the 19th-century botanist who extensively studied Indian flora.
- 🌱 Unlike annual soybean, Neonotonia wightii is a true perennial in tropical climates and can live 5+ years if not killed by frost, producing multiple harvests per year.
- 🌱 The plant was deliberately introduced to East Africa and Madagascar as a forage crop in the 1950s-60s and has become naturalized in many regions, transforming pastoral farming systems.
Gardening Terms
New to gardening? Learn about terms used in this guide:
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