Gadenin日本語Get the appThe seed coat is the first obstacle
Winged bean seed is small, square-shouldered and genuinely hard. Dropped on a table it rings rather than thuds. That coat is waterproof, and a proportion of every batch will refuse to take up water at all if you simply push it into the soil. Growers who report germination of one seed in four almost always sowed untreated seed into merely warm ground and blamed the seed supplier.
You have two reliable ways past it. Nick the coat, or soak it, or do both in that order. Nicking is the surer of the two because it works on the individual stubborn seeds rather than on the average. Either way, do it the same day you sow; a seed that has taken up water and is then left dry on a windowsill is dead.
- Nick the coat away from the eye Find the pale scar (the hilum) on one edge. Rub the opposite end on medium sandpaper, or take one careful pass with a nail clipper, until you see the paler layer under the shiny coat. Do not cut into the seed itself and never nick over the hilum, where the shoot emerges.
- Soak overnight in tepid water Twelve to eighteen hours is right. Swollen seeds roughly double in size and lose their sharp edges. Any seed still hard and small after eighteen hours has not imbibed, so nick it and give it a fresh two hours rather than soaking the batch longer.
- Discard the floaters that stay hard A seed that is both floating and unswollen after treatment is usually hollow or weevil-damaged. Throw it out rather than filling a station with it.
- Sow the same day Move swollen seed straight into warm, moist soil. Sitting in water past a day starts fermentation, and you will smell it before you see it.
Soil warmth, depth and spacing
This is a lowland tropical legume and it behaves like one. It wants soil above 68F (20C) at sowing depth and grows fastest in air temperatures between 77F and 90F (25C and 32C). Sown into soil in the low sixties Fahrenheit it germinates slowly, sulks at the two-leaf stage and never really catches up, even when the weather turns. Wait for settled warmth rather than pushing the date.
Sow an inch (2.5 cm) deep, two seeds per station, and thin to the stronger seedling. Give each plant 12 to 18 inches (30 to 45 cm) along the row with the row itself against the support. Closer than that and the lower half of the vine becomes a dark, damp tangle you cannot pick from.
| Soil temperature at sowing depth | Days to emerge | What to expect |
|---|---|---|
| Below 64F (18C) | Three weeks or never | Seed rots or stalls. Do not sow |
| 68F (20C) | 10 to 14 days | Workable but uneven |
| 77F (25C) | 5 to 8 days | Even, vigorous emergence |
| 86F (30C) | 4 to 6 days | Fastest. Keep the surface damp |
Choose an early type if your season is short
Most winged bean stock flowers only as the days shorten, and that single fact decides whether you get a crop or a monument. Sown in a place with a short warm season, an ordinary short-day type spends the whole summer making an enormous vine, starts flowering as the nights draw in, and is killed by the first frost with pods the size of a fingernail. The plant did nothing wrong; it was simply never going to reach the harvest before the cold arrived.
The way round it is to sow seed described as early, day-neutral or day-length-insensitive, which flowers on age rather than on night length and can be picking within about 75 to 90 days. If all you can get is short-day stock and your first frost comes early, grow it under cover where you can hold the season open into late autumn, or accept that you are growing it for the leaves, shoots and tubers rather than the pods.
Direct sowing versus starting under cover
Direct sowing is simpler and gives a better root system, because winged bean makes a deep taproot early and resents having it coiled in a pot. Where the warm season is long, sow direct at the foot of the support and be done with it.
Where the season is tight, three or four weeks of headstart under cover is worth the disturbance. Start in deep pots or root trainers at least 4 inches (10 cm) deep rather than in cell trays, sow one seed per pot, and keep the compost at 77F (25C) on a heat mat. Plant out only when night temperatures stay above 59F (15C) and the seedling has its first true leaves. Handle the rootball whole and do not tease the roots out.
Write down the sowing date, the soil temperature you sowed into, and how many of ten seeds came up. Germination percentage from your own conditions is the number that tells you next year whether to sow two seeds a station or three.
What to fix before the seed goes in
Winged bean fixes its own nitrogen once nodulated, so a bed dug through with fresh manure gives you leaf and vine and very little else. Work in well-rotted compost, make sure the drainage is genuinely free, and leave the nitrogen alone. Phosphorus and potassium matter far more here, and both feed the tubers as well as the pods.
The support has to be up before you sow, not after. These vines climb 8 to 12 feet (2.5 to 3.5 m) and become heavy and wind-catching, and driving posts in beside an established plant tears the taproot. Set the posts, string the netting, and then sow along the base.