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How to Grow Yardlong Bean, Black-seeded

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Yardlong Bean, Black-seeded

Vigna unguiculata subsp. sesquipedalis

vegetable

Yardlong beans (also called asparagus beans) are a vigorous vining legume producing long, slender pods that can reach 12-36 inches in length. The black-seeded variety is prized for its tender pods, mild flavor, and high productivity in warm climates. This Asian staple is more heat-tolerant than common snap beans and produces abundantly throughout the growing season.

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Example Yardlong Bean, Black-seeded timeline · Pittsburgh, PA (Zone 6b)

  1. Plant Yardlong Bean, Black-seeded

    Around Apr 17

    Near Pittsburgh's average last spring frost.

  2. Tend & protect

    Late spring–summer

    Watering, feeding, and pest-watch reminders.

  3. Harvest Yardlong Bean, Black-seeded

    Around Jun 16

    ≈ 60 days after planting

Sample dates for Pittsburgh, PA. Sign up to get exact Yardlong Bean, Black-seeded dates for your own zip code.

Growing Conditions

☀️
Sun: Full sun, 6-8 hours daily minimum; 8+ hours preferred for best production
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Water: Keep soil consistently moist but not waterlogged. Water deeply 1-2 times weekly; increase frequency during flowering and pod development. Reduce watering slightly once established to encourage deeper roots.
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Spacing: 4 inches
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Days to maturity: 60-75 days from planting to first harvest
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Planting depth: 1

Soil

Type: Well-draining loamy soil with good organic matter
pH: 6.0-7.0
Amendments:
Compost aged manure balanced fertilizer (5-10-10)

Growing Zones

Find your zone →

Thrives in zones 9-11; can be grown as an annual in zones 8 and warmer

9a 9b 10a 10b 11a 11b

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Growth Stages

1

Seedling

2-3 weeks

Seeds germinate within 7-14 days. Cotyledons emerge, followed by the first true leaves. Plants are delicate and small.

Keep soil warm (70-85°F) and consistently moist. Provide bright light. Do not transplant until at least 2-3 true leaves appear. Thin seedlings to proper spacing early.

2

Vegetative Growth

3-4 weeks

Rapid growth with elongating stems and compound leaves. Vines begin climbing and establishing a strong root system.

Provide sturdy stakes, trellises, or supports immediately. Water regularly and maintain warm temperatures (75-85°F). Apply compost or balanced fertilizer every 3-4 weeks. Pinch tips if needed to encourage branching.

3

Flowering

2-3 weeks, with continuous blooming possible

Delicate purple, pink, or white flowers appear in clusters along the vines. Flowers are typically self-fertile.

Ensure adequate water and consistent temperatures. Avoid excessive nitrogen, which promotes foliage at the expense of flowers. Pollination is generally excellent; no hand-pollination typically needed.

4

Pod Development & Fruiting

3-4 weeks per flush of pods

Long, thin pods develop rapidly from flower clusters. Pods elongate to 12-36 inches depending on variety and growing conditions. Black seeds become visible through pod walls as they mature.

Maintain consistent watering during this critical stage. Water stress reduces pod quality. Continue light feeding every 3-4 weeks. Ensure vines have adequate air circulation to prevent disease.

5

Harvest & Succession

8-12+ weeks

Pods mature continuously over 8-12 weeks or longer. Regular harvesting triggers new flower and pod production, extending the season.

Harvest pods when young and tender (8-10 inches long) for best quality. Check plants every 2-3 days. Handle vines gently to avoid breaking branches. Continue watering and light fertilization to sustain production.

Companion Planting

Plan your garden →

Plant with:

corn squash pumpkin maize cucumber tomato basil chives

Avoid planting near:

onion garlic fennel brassicas

Common Pests

  • Spray foliage with water to increase humidity; use neem oil or insecticidal soap if infestation is severe. Provide afternoon shade in very hot climates.

  • Spray with strong water stream; use insecticidal soap or neem oil. Encourage beneficial insects by planting flowers nearby.

  • Use yellow sticky traps; spray with neem oil or insecticidal soap. Remove heavily infested leaves.

  • Hand-pick in early morning; use row covers on young plants. Apply neem oil if populations are high.

  • Inspect pods regularly and remove infested ones. Use Bacillus thuringiensis (Bt) sprays if needed. Encourage natural predators.

Uses

🍳

Stir-fries & Asian cuisine

Culinary

Yardlong beans are a staple in Southeast Asian cooking, prized for their tender texture and mild, slightly sweet flavor. They are typically cut into shorter segments and quickly stir-fried with garlic, ginger, and soy sauce. [source]

🍳

Fresh vegetable preparation

Culinary

Young pods can be steamed, boiled, sautéed, or eaten raw in salads. They retain a tender-crisp texture and delicate flavor superior to common snap beans when harvested at the right stage. [source]

🍳

Dried beans & preservation

Culinary

Mature black seeds can be dried and stored for months, then cooked like traditional dried beans. They have a mild, slightly nutty flavor and creamy texture when cooked. [source]

🏠

Nitrogen fixation & soil improvement

Household

As a nitrogen-fixing legume, yardlong beans enrich the soil with bioavailable nitrogen through their root nodules. Leaving plant residue in the soil or using them as a green manure crop improves soil fertility for subsequent crops. [source]

🦋

Pollinator & beneficial insect support

Wildlife

The abundant flowers attract bees, butterflies, and other pollinators, supporting biodiversity in the garden. The dense vines also provide habitat for beneficial insects. [source]

Harvest Tips

Begin harvesting when pods are young and tender, typically 8-10 inches long (before they become tough and stringy). Harvest every 2-3 days to encourage continuous production. Pods should snap when bent. Use clean, sharp pruners to avoid damaging vines. Peak harvest typically occurs 60-90 days after planting and can continue for 8-12 weeks with proper care. Harvesting young pods extends the productive season considerably.

Fun Facts

  • 🌱 Yardlong beans are called 'asparagus beans' by some gardeners because their tender young pods bear a faint resemblance to asparagus spears in flavor and texture, and they are a favorite in Asian cuisines where asparagus is less commonly grown.
  • 🌱 The black-seeded variety is particularly prized in Chinese and Vietnamese cuisine; a single mature pod can reach up to 3 feet in length, though they are harvested much younger for optimal tenderness and flavor.
  • 🌱 Unlike common snap beans, yardlong beans prefer hot weather and actually thrive in the intense heat and humidity of tropical and subtropical regions, making them an excellent heat-tolerant alternative in southern gardens during peak summer months.

Gardening Terms

New to gardening? Learn about terms used in this guide:

Compost Full Sun Pollination Transplant Trellis True Leaves
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