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Winged bean asks for more warm weeks than almost anything else in a temperate vegetable garden. From sowing to first pod is about 75 to 90 days on an early type and anything from 120 days to never on a short-day type grown at high latitude. The whole plan therefore hangs on one question asked before you sow: how many frost-free weeks do you actually get?
Count the weeks from the date your soil reliably passes 68F (20C) to the date of your first autumn frost. Fewer than fourteen and you need an early type, a headstart under cover, or a hoop house. Sixteen to twenty and an early type outdoors will crop well. More than twenty-two and you can grow short-day stock and dig tubers too.
| Stage | Trigger | What you do |
|---|---|---|
| Preparation | Weeks before the soil warms | Compost worked in, no fresh manure, supports built and braced |
| Sowing | Soil steadily above 68F (20C), frost gone | Scarify or soak, sow an inch (2.5 cm) deep, two per station |
| Establishment | First two to three weeks after emergence | Thin to one, guide the vine onto the support, slug protection |
| Climbing | High summer | Water deeply, mulch, no nitrogen, pinch the tip at the top of the frame |
| Flowering | As nights lengthen, or on age for an early type | Switch to high-potassium feed, keep water absolutely steady |
| Cropping | About 10 to 14 days after each flower | Pick at 3 inches (8 cm), every two days, without exception |
| Seed and tubers | After the pods finish, until the top dies | Leave a few pods to dry, keep feeding potassium, then lift the roots |
Early season: get the ground and the frame ready
Everything that involves digging happens before the seed goes in. Work in well-rotted compost, correct the drainage on heavy ground by ridging or raising the bed, and leave the nitrogen alone; this plant makes its own and an over-fed bed produces vine instead of pods. A dressing of a potassium-rich amendment along the row now is money well spent, particularly if you intend to dig tubers.
Build the support at the same time. Posts 18 inches (45 cm) into the ground, no more than 6 feet (1.8 m) apart, netting of 4 to 6 inch (10 to 15 cm) mesh, and the end posts braced. Driving posts in later, beside an established plant, tears the taproot and sets the vine back a fortnight.
Mid-season: climbing, then the switch to flowering
From emergence to the top of the frame the plant does almost nothing but grow, and your job is simply to keep it watered deeply, mulched once the soil is thoroughly warm, and off the ground. Guide the first foot of stem onto the netting and after that it twines itself. When the leader reaches the top of the support, pinch it out; the side shoots that follow carry most of the flowers.
The switch to flowering is the moment the whole crop turns. Stop any feed that contains much nitrogen, move to a high-potassium liquid feed every two weeks, and let nothing interrupt the watering, because buds abort within days of a dry check. Thin a few of the oldest interior leaves so that light reaches the pods forming inside the canopy.
- Pinch the leader at the top of the frame Take out the growing point once it reaches the top. Side shoots below carry the flowers, and an unpinched vine piles growth up out of reach.
- Change the feed at first bud From the first visible flower bud, every feed is a high-potassium one. Nitrogen at this stage converts flowers back into leaves.
- Fix the watering rhythm now Two or three deep soakings a week at the root, mulched. Daily light sprinkles are what cause bud drop when the first heatwave arrives.
- Open up the middle of the plant Remove a handful of the largest old leaves from the congested interior so you can see daylight through the vine and reach the pods.
Late season: picking hard, then letting it finish
Once pods start, the calendar becomes a two-day picking round and stays that way for six to ten weeks. Pods reach eating size about 10 to 14 days after the flower opens and are fiber a few days later, so a missed week costs you a flush as well as the pods themselves. Keep stripping the overgrown ones off; a filled pod tells the plant its work is done.
Towards the end, stop picking a few pods on the healthiest plants and let them run on to brown, dry and rattling for seed. Keep the potassium feed going while the plant is still green, because the tubers are bulking up under the ground long after the pods above have stopped. When the top growth yellows and dies back, fork a wide circle well outside the crown and lift the root mass by hand.
Record four dates every year: the sowing date, the emergence date, the first flower, and the first pod worth eating. Note the position of each plant in the row too. Within two seasons those dates tell you whether your ground and your season need an early type, and whether the wet end of the bed is worth sowing at all.
Clearing up and the ground afterwards
Cut the top growth off at ground level rather than pulling it, unless you are digging tubers, and leave the nitrogen-fixing roots in the soil for whatever follows. Compost healthy vine material; bin anything that carried leaf spot, and bin the roots outright if you found nematode galls. Take the netting down, clean it and store it dry, because a season of this vine leaves a dense mat of dried stem that is far harder to remove in spring.
Follow winged bean with a leafy crop that will use the nitrogen left behind, and do not put another legume on the same ground for three years. Dry the seed you saved until a bean shatters rather than dents under pressure, then store it cool, dark and airtight. It stays viable for several years, which is useful, because the season you most want it is the one where you can start early.