From Vines and Bushes to Thai Cooking Vegetables: Growing Yardlong Beans

Yardlong beans, also known as asparagus beans or Chinese long beans, are a staple in Thai cuisine, prized for their crisp texture and slightly nutty flavor. Unlike common green beans, their pods can grow up to 36 inches long, though they are best harvested at 12–18 inches for tenderness. These vigorous climbing vines are easy to grow in warm weather, producing abundant harvests from mid-summer until frost. In the Thai kitchen, they are essential for dishes like pad prik king (dry curry with long beans) and som tam (green papaya salad), where their crunch and ability to absorb flavors shine.

What Are Yardlong Beans?

Yardlong beans (Vigna unguiculata subsp. sesquipedalis) are a type of cowpea grown for their edible immature pods. They are closely related to black-eyed peas but are harvested before the seeds develop. The pods are slender, round, and flexible, ranging in color from pale green to deep purple, depending on the variety. When cooked, they have a dense, slightly chewy texture and a flavor that is more bean-like and earthy than common snap beans. In Thai markets, they are often sold in bundles, their long, curling pods creating a striking visual display.

How Long Does It Take for Yardlong Beans to Grow?

From sowing to first harvest, yardlong beans typically take 60 to 80 days. They are a warm-season crop that grows quickly once soil temperatures reach at least 65°F (18°C). The plants begin flowering about 6–8 weeks after germination, and pods are ready to pick 2–3 weeks later. Regular harvesting encourages more production, so you can continue picking for several months in a long growing season.

Yardlong Bean Growing Season and Temperature

Yardlong beans thrive in hot, humid conditions and are more heat-tolerant than common beans. They require a long, warm growing season with daytime temperatures between 75°F and 95°F (24°C–35°C). Night temperatures should stay above 60°F (15°C) for good pod set. In cooler climates, you can start seeds indoors 3–4 weeks before the last frost and transplant after the soil warms. In tropical and subtropical regions, they can be grown year-round.

Yardlong Bean Growing Zones and Conditions

Yardlong beans are suitable for USDA hardiness zones 5–11 when grown as an annual, but they perform best in zones 8–11 where summers are long and hot. They need full sun (at least 6–8 hours daily) and well-drained soil with a pH between 6.0 and 7.5. Work compost into the soil before planting to improve fertility and moisture retention, but avoid high-nitrogen fertilizers, which promote leafy growth at the expense of pods.

Growing Yardlong Beans in the UK

In the UK, yardlong beans can be grown in a greenhouse or polytunnel, or outdoors in a very warm, sheltered spot during a hot summer. Start seeds indoors in late April or May, and transplant only when temperatures are reliably above 60°F (15°C). A south-facing wall or fence can provide extra warmth. Even with these precautions, yields may be lower than in tropical climates, but a greenhouse can produce a good crop.

Planting and Trellising Yardlong Beans

Yardlong beans are climbing vines that can reach 8–12 feet tall, so they need strong support. A trellis, fence, or teepee made of bamboo poles works well. Here’s how to plant them:

1. Sow seeds directly in the garden after all danger of frost, when soil is at least 65°F (18°C). Plant seeds 1 inch deep and 3–4 inches apart in rows.
2. Thin seedlings to 6–8 inches apart once they have two sets of true leaves.
3. Provide support at planting time. Install a trellis or poles at least 7 feet tall; the vines will twine around them.
4. Water regularly, keeping soil evenly moist but not waterlogged. Mulch to retain moisture and suppress weeds.
5. Fertilize lightly with a balanced organic fertilizer when plants begin to flower, but avoid excess nitrogen.

In warm soil, seeds germinate in 7–10 days. The vines grow rapidly, and flowers—typically pale purple or white—appear in clusters.

Harvesting Yardlong Beans

Harvest yardlong beans when the pods are 12–18 inches long and about the thickness of a pencil. They should be firm and snap when bent. If left too long, they become tough and stringy. Pick every 2–3 days to keep plants productive. Use scissors or pinch the stem to avoid damaging the vine. Fresh beans can be stored in the refrigerator for up to a week.

Using Yardlong Beans in Thai Cooking

In Thai cuisine, yardlong beans add a crisp, juicy crunch and a mild, slightly sweet flavor that pairs well with bold seasonings. They are often cut into 1–2 inch pieces and used in stir-fries, curries, and soups. Their dense texture holds up well to high-heat cooking methods.

Key Thai Dishes Featuring Yardlong Beans

• Pad Prik King: A dry red curry stir-fry with yardlong beans, pork or chicken, and kaffir lime leaves. The beans absorb the spicy, aromatic curry paste while retaining their crunch.
• Som Tam: In this green papaya salad, raw yardlong beans are cut into short pieces and pounded lightly with garlic, chilies, tomatoes, lime juice, fish sauce, and palm sugar. They add texture and a fresh, green flavor.
• Gaeng Liang: A light, peppery vegetable soup that often includes yardlong beans, pumpkin, and Thai basil. The beans contribute body and a pleasant bite.
• Pad See Ew: While not traditional, yardlong beans can replace Chinese broccoli in this popular stir-fried noodle dish, offering a similar crunch.

Preparation Tips

Wash the beans and snap off the stem end. Cut into the desired length. For salads, blanch them briefly in boiling water for 1–2 minutes, then plunge into ice water to preserve color and crunch. For stir-fries, add them early so they cook through but remain crisp. Yardlong beans can also be pickled or added to curries for a hearty texture.

Yardlong Beans vs. Common Green Beans

While common green beans can be substituted in some Thai dishes, they lack the characteristic chewiness and subtle nuttiness of yardlong beans. For the most authentic results, yardlong beans are worth seeking out at Asian grocery stores or growing yourself.

Quick Reference: Growing Yardlong Beans at a Glance

• Days to harvest: 60–80 days from sowing
• Soil temperature for germination: 65–85°F (18–29°C)
• Ideal growing temperature: 75–95°F (24–35°C)
• Sun exposure: Full sun
• Support: Trellis, fence, or poles at least 7 feet tall
• Spacing: 6–8 inches between plants
• Water: Keep soil evenly moist; do not overwater
• Harvest: When pods are 12–18 inches long and pencil-thick