Vigna unguiculata subsp. sesquipedalis
Yardlong bean
Common names: Asparagus bean, Snake bean
At a glance
- Light
- Full sun
- Spacing
- 20 cm, rows 60 cm
- Lifespan
- Annual
- Sowing
- May–Jun
- Harvest
- Jul–Sep
- Hardiness
- Cold damage below 2 °C
- Water need
- Medium
Photo: David · Public Domain · Source
Description
The asparagus bean (Vigna unguiculata subsp. sesquipedalis) is a heat-loving climbing plant in the legume family. It produces long, slender pods that can reach 40 to 70 cm in length on vines that may grow up to three meters tall. Originating from Southeast Asia and West Africa, it prefers warm, frost‑free conditions and thrives best in a protected, sunny spot with a sturdy trellis. Raw pods and seeds contain lectins that can cause gastrointestinal upset, so they should be cooked before consumption. Pods are harvested young and crisp, before the seeds become visible; cooked, they have a mild, nutty flavor and remain tender.
Care instructions
Sow after the soil has reliably warmed, typically mid‑May (week 20). Provide a tall trellis early so the plant can climb. Water regularly, especially during dry spells while flowering. Use a fertile, loose soil that retains moisture but avoids water‑logged spots. Harvest pods every few days once they reach full length; this encourages further flowering and extends the harvest into early autumn.
The care notes were machine-translated from German.
Garden year
SowingMay–Jun
HarvestJul–Sep
Germination
- Soil temperature
- from 15 °C, ideally 25 °C
- Days to sprout
- 6 to 12 days
- Light
- Sprouts in light or dark
- Sowing depth
- 3 cm
- How to start
- Sow straight into the bed
Soil & site
Soil pH
Soil type
well-drained, humus-rich, nutrient-rich, loamy
The yardlong bean likes loose, humus-rich soil that stores warmth well and avoids waterlogging. A nutrient-rich, deep garden soil with good structure makes it grow best. In cold, compacted soils it germinates only hesitantly, so it is worth preparing the soil loosely before sowing.
Grow yardlong beans on the same plot again after 4 years at the earliest, to prevent soil fatigue. As a nitrogen fixer, it is a valuable preceding crop for heavy feeders such as cabbage or tomatoes.
Feeding
Medium feeder
Months
Jun–Aug
Mature compost at planting provides a good basic supply of nutrients. During the main growing season in summer, the yardlong bean welcomes an extra dose of organic fertiliser such as nettle liquid. As a legume, it fixes nitrogen from the air itself through its root nodules, so moderate feeding is enough overall.
Overwintering
The yardlong bean is an annual and sensitive to frost, so overwintering in the bed is not possible. After the last harvest in autumn, clear away the plant remains and put them on the compost. You can leave the roots in the soil, as the nitrogen nodules they contain benefit the following crops.
Propagation
Methods
- From seed
Propagation is by seed only. Because the yardlong bean loves warmth, sow directly outdoors only after the Ice Saints, or start it on the windowsill from April. The seeds germinate reliably within 1 to 2 weeks at soil temperatures from about 18 degrees. Small pots are enough for an early start, and the young plants move from them into the bed after the last night frosts.
Companion planting
Good neighbors
cabbage family (Brassicaceae)
particularly well establishedLeguminous plants collect nitrogen in the soil, from which Brassicaceae benefit as heavy feeders.
For example White cabbageKohlrabiRadishKalebroccolicauliflower and 41 more species in the catalogue
Source: classic companion planting (DACH-Gartenpraxis)
carrot family (Apiaceae)
Peas and beans provide carrot and celery with nitrogen and grow as shallow-rooted plants without competition next to each other.
For example CarrotCeleriacDillParsleyFlorence fennelCoriander and 21 more species in the catalogue
Source: classic companion planting (DACH-Gartenpraxis)
Rather not
amaryllis family (Amaryllidaceae)
particularly well establishedAllium species inhibit the nitrogen‑fixing rhizobia of legumes through their root exudates, which slows their growth.
For example GarlicOnionLeekChivesWild daffodilRocambole and 12 more species in the catalogue
Source: basic crop‑rotation rule
Companion planting is partly traditional gardening lore. Where the reason is known, it is given.
Some of these explanations were machine-translated.
For your garden
Grow Yardlong bean yourself
Gartenkern tells you when frost is coming, when to sow and when to harvest, for your location.
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