Vegetable
Yardlong Bean
Vigna unguiculata subsp. sesquipedalis · Fabaceae
Also called: Asparagus bean, Chinese long bean, Snake bean, Long-podded cowpea, Dau gok
Yardlong Bean (Vigna unguiculata subsp. sesquipedalis) is a moderate-water vegetable well suited to Tucson and the low desert. It thrives in full sun, with a fast growth rate.
Yardlong Bean at a glance
- Water use
- Moderate (established)
- Sun
- Full sun (6+ hours); tolerates and actually prefers Tucson's intense summer heat better than common snap beans.
- Mature size
- Climbing vine 6-9 ft tall on a trellis; pods 12-30 in long.
- Growth rate
- Fast
- Bloom
- Pale violet to lavender (also white/yellowish forms), Summer; harvest pods roughly 60-90 days from sowing, continuing through the warm season.
- Cold hardiness
- Frost-tender, heat-loving annual; needs warm soil (~65 F+) to germinate and is killed by Tucson's winter frosts. Grown only in the warm season.
- Soil
- Well-drained, fertile loam amended with compost; tolerates a range of soils, prefers slightly acidic to neutral pH.
- Native range
- Tropical Asia (cultivated subspecies of the African/Asian cowpea, Vigna unguiculata)
- Best used as
- Edible long pods (stir-fry, sauteed, curries), Vertical/trellis vegetable, Heat-tolerant summer green bean substitute, Nitrogen-fixing soil builder
- Wildlife
- Flowers attract bees and other pollinators.
- Toxicity
- Pods and immature seeds are edible when cooked; like other legumes the raw mature dry seeds should be cooked before eating. Not considered toxic to pets at normal exposures.
How to grow Yardlong Bean in Tucson & the low desert
Watering
Warm-season crop for Tucson: direct-sow seed after the soil is reliably warm, roughly mid-March through July, so it crops through the heat and monsoon. Keep soil consistently moist while flowering and podding; in summer heat that often means deep watering every 2-3 days (more in a heatwave). Mulch to conserve moisture and moderate soil temperature.
Fertilizer & nutrients
As a legume it fixes much of its own nitrogen, so go light on nitrogen. Work compost into the bed at planting; a single side-dressing of a balanced or phosphorus-leaning fertilizer when vines start running is plenty. Excess nitrogen yields foliage at the expense of pods.
Pruning & care
No true pruning. Provide a sturdy 6-8 ft trellis and train the climbing vines upward. Harvest pods frequently while young and pencil-thin (12-18 in) to keep the plant productive.
Notes
One of the best 'green beans' for the low desert because it sets pods in temperatures that cause common bush/pole beans to drop blossoms. Thrives in monsoon humidity. Pick young for tenderness; older pods get tough and starchy.
Sources: University of Arizona Cooperative Extension / Pima County Master Gardeners low-desert vegetable guidance; Growing in the Garden (Arizona low desert planting guide); Tucson Organic Gardeners Planting Guide