Gadenin日本語Get the appThe shape of the season
An adzuki season has an unusual shape because the crop is a short-day plant. From sowing until the nights are long enough, which in most temperate gardens means late summer, the plant does nothing but build leaves and roots. Then the daylength signal arrives, it flowers for several weeks, sets pods, and those pods ripen unevenly over another few weeks before you finish drying them under cover. Sowing to dry pods takes 90 to 120 days depending on how warm your summer is.
This means the two halves of the season need completely different attention from you. The first half is weeding and patience, and the plant will forgive you for ignoring it. The second half, from the first flower onward, is when everything is decided: water during pod fill, watching for aphids and pod borers, and then a harvest that runs for weeks rather than a single picking day.
The calendar below is written by stage rather than by month, so it reads the same in either hemisphere. Work backwards from your first expected autumn frost: the crop needs 90 to 120 days, and the last three or four weeks of that should be dry ripening weather. If the arithmetic is tight, sow at the earlier end of your window, and if it is comfortable, sow later rather than earlier, because early sowing buys leaves and nothing else.
| Stage | Trigger | What to do | What can go wrong |
|---|---|---|---|
| Bed choice | Before sowing | Pick a sunny, free-draining, unenriched bed with no legume for three years | Rich or wet ground gives leafy plants, lodging and root rot |
| Sowing | Soil above 60F (15C), well after the last frost | One inch (2.5 cm) deep, rows 18 to 24 inches (45 to 60 cm) apart | Cold soil rots seed; very early sowing adds only leaf |
| Emergence | Five to ten days after sowing | Net or row cover against birds and slugs until three true leaves | A stripped row does not recover |
| Thinning | At the first true leaf | Snip to one plant every three to four inches (8 to 10 cm) | A crowded row holds damp around the lowest pods later |
| Leafy growth | Weeks two to eight after emergence | Weed hard, add no feed, water only if the surface bakes | Weeds bury a slow young plant; nitrogen makes it flop |
| Earthing up | Plants about eight inches (20 cm) tall | Draw soil an inch or two (3 to 5 cm) against the stem bases | Unsupported rows lodge when the pods are heavy |
| Flowering | Nights lengthening in late summer | Soak weekly if dry, check tips for aphids twice a week | Drought or aphids now drop flowers and empty the pods |
| Pod fill | Green pods swelling, seed outlined through the wall | Keep the soak going, pick off any pod with a borer hole | Flat pods mean stress at flowering; borers eat the seed |
| First pods turning | Pods yellowing and going papery | Stop watering completely, start walking the rows | Rain now blackens pods and can sprout seed in the pod |
| Harvest | Pods fully tan and rattling | Pick over every three or four days, or pull whole plants at three quarters tan | Waiting for the last pod loses the first ones to splitting |
| Drying and threshing | One to three weeks under cover | Dry until a bean will not dent, beat in a sack, winnow with a fan | Jarring damp beans leads to mold within weeks |
| Weevil treatment | Before anything goes on the shelf | Freeze sealed at 0F (minus 18C) for a week, or heat to 140F (60C) for two hours | Untreated jars are hollowed out from the inside months later |
| Clearing the bed | After the last plants come out | Destroy debris, leave the roots in the soil | Old pods shelter weevils and carry disease over |
The four moments that decide the crop
Most of this calendar is undemanding and an adzuki bed will look after itself for weeks at a stretch. Four moments carry nearly all the risk, and recognizing them lets you ignore the rest with a clear conscience.
The first is the sowing date, which should be later than instinct suggests. Warm soil and a compact plant beat an early start, because the flowering date will not move to reward you. The second is the flowering window: from the first flower to full pods the bed needs a weekly soak in dry weather and a look over for aphids and borers twice a week, and neglect here costs pods directly. The third is the decision about how to harvest, which is a judgement between picking over the rows for weeks and pulling everything the moment the forecast turns. The fourth is the weevil treatment, which happens after the gardening is finished and which people forget precisely because the crop is already safely in a jar.
Everything else, the weeding and the earthing up and the occasional watering during leaf growth, is ordinary garden work that can slip by a few days without consequence. Concentrate on the four that cannot.
- Count back 120 days from your first autumn frost That gives the latest safe sowing window. Sow at the warm end of it once the soil is above 60F (15C) rather than at the earliest date the frost allows.
- Diarise the earthing up at about eight inches (20 cm) Roughly three to four weeks after emergence. Draw soil against the stems whether or not the row looks like it needs it yet, because late support achieves very little.
- Switch to weekly soaking at the first flower From that date until the pods are full, a deep weekly watering in dry weather is the single job with the most direct effect on how many beans you end up with.
- Start walking the rows as the first pods yellow Every three or four days from then on. Pods split within days of turning tan, so a weekly pass is already too slow and loses the earliest seed to the soil.
- Do not jar the beans until they will not dent The thumbnail test is the last gate of the growing season. Everything you did over four months is undone by sealing beans at 15 percent moisture.
- Treat every batch for weevil before it goes on the shelf Freeze sealed for a full week, or heat if you will not sow it. Write the date and method on the jar label so you know months later that it was done.
Where adzuki fits in the rest of the garden
The crop occupies a bed from late spring right through to autumn, a long tenancy for a small yield, so put it where the length of stay is not a problem. It fixes its own nitrogen, so it does well on ground that has just grown something hungry, and it leaves that ground better than it found it.
Leave the roots in the soil when you clear the bed, or cut the plants at the base if pulling lifts the roots. The nodules hold fixed nitrogen that releases as they break down, and whatever you plant there next season notices it. Threshed straw can go back to the same ground provided the crop was healthy, but if you saw leaf spot, blight or pod mold, destroy it instead.
Because the bed does not come free until autumn, plan the follow-on crop as something sown late or planted the following spring rather than a quick catch crop. And keep the three-year rule: no legume back on that ground until two full seasons have passed.
The record that makes the second year better
Seven entries cover the whole season: the sowing date and the soil temperature you measured, the emergence date, the date the first flower opened, the date the first pod turned tan, your first and last picking dates, the cleaned bean weight against the area sown, and the date and method of the weevil treatment. Written down as they happen, they turn an unfamiliar crop into one you can plan.
The first flower date is the most valuable of them by a wide margin. On a short-day plant that date barely moves between seasons at your latitude, so once you have it you can predict the flowering window, the watering period and the harvest weeks for every year afterwards, and you can set your sowing date to arrive at a compact, well-fed plant exactly when the nights start to lengthen.
Add two notes alongside the dates. Record whether the rows lodged and after what weather, because that decides whether the fix is wider spacing, earlier earthing up or a more sheltered corner. And record what the weather did in the fortnight before your main harvest, because if ripening keeps colliding with rain, the answer is to pull whole plants earlier next time. Keep the bed position on the same note, for the three-year rotation and because you will want to know which corner is due the nitrogen this crop leaves behind.