- Type
- Legumes
- Difficulty
- Easy
- Season
- Summer
- Sowing
- From seed
Adzuki Bean
Vigna angularis
Starch, saponins · the legume you sow in June
Adzuki is an annual legume for the open plot. It goes in late, in June or July, so it slots straight into ground just cleared of potatoes or garlic and lets one bed carry two crops in a season. The pods do not ripen together, so pick the browned ones in two or three passes. The Donguibogam lists it in the Grain section as 赤小豆, giving it a neutral nature, though some call it slightly cold and others warm, with a sweet and sour taste and no toxicity. The same entry names the leaf 藿 and the flower 腐婢, and notes that the flowers are gathered in the seventh lunar month and dried in the shade.
Year-Round Calendar
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Where It Grows
- Main producer Produces most of the world's adzuki beans. Heilongjiang and Jilin in the northeast, along with North China, are the centre.
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Main producer
The Tokachi Plain in Hokkaido is the centre, where cool summers swell the beans. Harvest September, October
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Major producer
Grown as a second crop in dry fields nationwide. Landraces from the mountains of Gangwon and North Jeolla are known. Harvest October, November
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Wild adzuki grows across Korea, China and Japan, and it was domesticated in East Asia as well, so its origin cannot be pinned to a single country and no origin row has been entered. Production and consumption still remain almost entirely within these three countries, so the list of growing regions cannot be extended further. A small amount is grown in the northwestern United States and in Canada for export to Japan, but the scale is small and it has not been included.
- Optimum
- 20~25℃
- Range
- 10~35℃
- Hardiness
- Not hardy
- Day length
- Short-day
A summer crop. It is short-day — flowers set as the days grow shorter, so even a late sowing ripens in time for autumn. It is more sensitive to waterlogging than soybean: the roots are damaged where water collects, and if rain is frequent as the pods ripen, the beans sprout in the field. Frost kills it.
In Korea Nationwide
It is grown as a second crop, sown in June–July where potatoes or garlic have been lifted. The pods do not ripen all at once, so they are picked in two or three passes in October–November.
How to grow
- Light
- Six hours of direct sun or more. In shade the plants set fewer flowers
- Soil and depth
- Free-draining field soil. It tolerates poor ground but not a spot where water stands
- Spacing
- 20 to 25cm between plants, 60cm between rows. Two or three seeds per hole, thinned later to one or two plants
- Watering
- Keep the soil from drying at flowering and while pods fill. Otherwise water sparingly
- Feeding
- Rhizobia supply the nitrogen. Base-dress with phosphorus and potassium; heavy nitrogen pushes the plant into leaf and knocks it over
- Harvest
- Pick the pods that have dried brown, in two or three passes. They do not ripen together. Dry cut plants a few more days before threshing
What makes the difference. Sowing in late June or early July, straight after potatoes or garlic come out, is not too late. It works well as the second crop of the season in one bed
Why this one is harder. Fully ripe pods split open in dry sun and scatter the beans. Picking browned pods as they come, rather than waiting, is what protects the yield
Common problems
- Bean bug (Riptortus pedestris) You will see Pods form but the beans never fill, leaving empty husks What to do Hand-collect in the cool of the morning or set a pheromone trap. Watch hardest while pods are filling
- Adzuki bean weevil You will see Small holes in the stored beans with fine dust beneath them What to do Freeze for three or four days straight after harvest, then store airtight and cool. Sort out any bean already holed
- Aphids You will see Colonies on new shoots and flower stalks, turning sticky What to do Wash off with a jet of water; if it recurs, use an egg-yolk oil spray or an approved organic product
This page describes how a crop is grown and used. It does not claim health effects for any food, nor is it intended to prevent or treat disease. Component and study notes are references only and do not mean the same result occurs in people. Consult a medical professional about health concerns.
Health Benefits
What the Donguibogam records — nature, taste, seed, leaf and flower. The Donguibogam lists adzuki in the Grain section as 赤小豆. It gives the bean a neutral nature, while noting that some call it slightly cold and others warm, with a sweet and sour taste and no toxicity. For medicinal use it directs that early-sown, deeply red beans be chosen, saying late-sown ones are weaker. It names the leaf 藿 and the flower 腐婢, notes that the flowers are gathered in the seventh lunar month and dried in the shade, and adds that long consumption leaves the body dark, thin and dry. This is a historical medical record and differs from modern medical judgment.
Analysis of seed-coat pigments. Proanthocyanidins and catechin-type polyphenols have been reported in the adzuki seed coat. The accompanying explanation attributes the red, astringent first boiling water to these compounds leaching out alongside the saponins. This is compositional analysis, not a statement about effects.
Starch and fibre composition. Composition tables list dried adzuki at about 68g of carbohydrate and over 10g of dietary fibre per 100g. Set against cereal grains, that is a high fibre share. The entry stays with the compositional record.
Nutrition
- Starch (carbohydrate) (about 68g per 100g, dried) — the main carbohydrate of the bean
- Protein (about 20g per 100g, dried) — plant protein
- Saponins (leach into the first boiling water) — glycosides that foam
- Polyphenols (proanthocyanidins, catechins) (concentrated in the red seed coat) — polyphenols reported in adzuki seed coat
Starch and protein Dried adzuki runs about 68g of carbohydrate and about 20g of protein per 100g. Fat sits around 1g, very low even among legumes. That is why adzuki is never pressed for oil but cooked down into paste and porridge. Soaked and boiled, the beans gain a little over double their weight.
Dietary fibre Dried adzuki is reported at over 10g of fibre per 100g. Most of it sits in the seed coat and cotyledon, so a fine paste sieved free of skins carries much less. Whole beans cooked into rice and sieved paste are compositionally different foods from the same bean. A large helping at once can bring on gas.
Saponins and the first boiling water The first water off a pot of adzuki runs red, astringent and foaming. That is the saponins and polyphenols of the skin coming out. Discarding that first water and refilling the pot is the old method for taking the astringency down. It also takes the pigment with it, so the finished colour is paler.
Potassium Composition tables put dried adzuki above 1,000mg of potassium per 100g. A good share of it leaves with the soaking and boiling water. Whether the cooking liquid is discarded or kept decides how much reaches the bowl. Anyone advised to manage their potassium intake should follow the guidance of their own doctor or dietitian.
Pairings
○ Rice and glutinous rice — Adzuki adds the lysine that rice is short of. Par-boil dried beans separately until half done, then add them to the rice. Put both in raw and the rice will be cooked while the beans are still hard.
○ Sorghum and other mixed grains — The astringency of the bean skin and the toasty note of the grain hold each other in check. Long-standing dishes such as sorghum-and-adzuki rice cake come out of that. The grains cook faster, so the beans go in first. Sorghum
○ A pinch of salt — Sweetened bean paste made with sugar alone tastes flat and drawn out. A very small pinch of salt at the end sharpens the outline of the sweetness. Add it just before the heat goes off.
△ Raw or undercooked beans — Adzuki is not eaten raw. Like other legume seeds it carries lectins and digestive inhibitors, and undercooked beans can bring stomach pain and nausea. Soak them, then boil hard for long enough; a long, low simmer alone is not a safe substitute. Beans destined for shaved ice get the same full boil.
△ Stored beans with bean weevil — Left as harvested, adzuki bean weevil lays eggs and the larvae eat out the inside. Even beans that look sound should be sorted out if you see small holes and fine dust. Three or four days in the freezer straight after harvest clears the eggs. After that, store airtight somewhere cool.
△ Confusing the bean with sweetened products — The bean itself is barely sweet at all. Commercial sweet bean paste and yokan carry a high proportion of sugar and should be read as different foods from the bean in the composition table. Eating more of them because they contain adzuki does not follow.
Varieties
- Arari (seed) — A widely grown red adzuki line. Fairly even beans
- Local red adzuki (seed) — The landrace grown along field edges. Ripens unevenly, so pick in passes
- Black adzuki (seed) — Black seed coat. Colours rice deeply when cooked in
- White adzuki (seed) — Pale or white coat. Kept separate for a lighter-coloured paste
Source: Donguibogam, Grain Section 赤小豆 · Rural Development Administration (Nongsaro) · Korean Food Composition Table