Gadenin日本語Get the appSteady moisture, not heavy watering
Splitting is the failure that most often ruins an otherwise good daikon, and it is caused by a swing rather than by a level. The root's outer tissue stops expanding during a dry spell, then heavy rain or a heavy watering makes the inside swell again faster than the skin can stretch, and the root cracks from the shoulder down. The crack is usually visible within two days of the rain.
So the aim is a soil that never goes bone dry and never sits saturated. Push a finger in to the second knuckle; if it comes out dry, water thoroughly and slowly until the soil is wet several inches down, then leave it alone until it dries again. Little and often keeps only the surface damp and encourages shallow roots.
During the last three weeks of bulking the root is most vulnerable, because it is expanding fastest. If a long dry spell breaks with forecast heavy rain at that stage, water lightly beforehand so the change is less abrupt.
| Stage | Watering | Watch for |
|---|---|---|
| Sowing to emergence | Keep the surface just moist | Crusting, half empty stations |
| Seedling to thinning | Water thoroughly when dry an inch down | Stretched, leaning seedlings |
| Rapid bulking | Deep soak every few dry days | Wilting at midday, then recovering |
| Final three weeks | Even moisture, avoid extremes | Splitting after heavy rain |
Midday wilting that recovers by evening in hot weather is normal and not a signal to water. Leaves still limp in the early morning are the real signal.
Feed twice, lightly, after thinning
Daikon grows leaf first and root second. Nearly all the root weight goes on in the second half of its life, so the useful feeding is after the plants are thinned to one per station, not at sowing. Two light top dressings placed between the rows will do more than one heavy one.
Scatter the feed along the row, not against the stem, then hoe it in shallowly and draw a little soil up as you go. Granules resting against the shoulder scorch it, and feed sitting on dry soil does nothing until it rains.
- First feed at the second thinning When you take each station down to one plant, scatter a light dressing between the rows, hoe it in and firm the soil back around each plant. This is the feed that builds the leaf area that later fills the root.
- Second feed three weeks later Repeat once the leaves have closed over the row. This is the feed that fills the root. After this point stop feeding entirely; late nitrogen makes soft roots that go hollow.
- Read the leaf color Pale yellowish outer leaves mean the plant is short of nitrogen. Very dark, floppy, oversized leaves mean it has had too much and the root will lag behind.
If the leaves are enormous and the shoulder is still narrow at two thirds of the expected days, cut the base dressing by a third next season rather than adding another feed now.
Draw soil up over green shoulders
As the root swells it pushes its shoulder above the soil, and the exposed part turns green and slightly bitter, and in cold weather it is the first part to be frost damaged. Drawing soil up over the shoulder every few weeks fixes all three problems at once and also steadies the plant against wind.
Do it with a hoe or your hands, taking soil from between the rows and mounding it against the plant so that no more than an inch of shoulder shows. Keep the soil below the growing point where the leaves emerge, because burying that causes rot.
| Timing | Job | Why |
|---|---|---|
| At the second thinning | Firm soil back around the base | Stops the plant rocking in wind |
| Two to three weeks later | Draw soil over the shoulder | Prevents greening and bitterness |
| When the shoulder shows again | Repeat, with the second feed | Root is expanding fastest here |
| Before the first hard frost | Mound soil high over the shoulder | Protects the exposed crown |
Weeding, mulch and keeping the leaves upright
Weed early and shallowly. Once the daikon canopy closes it suppresses almost everything, so the only critical period is the first month, and that is exactly when deep hoeing will cut the taproot. Hand weed close to the plants and keep the hoe an inch deep and well away from the stations.
A light mulch of straw between the rows after the second feed evens out soil moisture, which is the best insurance against splitting, and keeps rain from splashing soil onto the lower leaves. Keep it a couple of inches clear of the stems so the shoulders are not sitting in damp mulch.
Heavy leaf that flops sideways after wind or rain shades the crown and holds moisture against it. Lift the leaves back upright and mound a little soil, rather than tying or cutting them, since removing leaves at this stage directly reduces the size of the root.
Keep a simple record of the growing season
Three things are worth writing down while the crop is growing, and none of them take a minute. The date of each thinning and feed, so you can see whether the second feed is landing at the right point in the bulking period. The date of any heavy rain following a dry spell, which will explain any splitting you find at harvest. And the date you first saw a pest, by row position.
Photograph the bed at the second feed and again three weeks later. Comparing leaf size between seasons is the quickest way to tell whether you are over or under feeding, and it is far more reliable than trying to remember what last year's plants looked like.