Gadenin日本語Get the appThe crop is a race, so keep it moving
A turnip that grows fast and without a check is mild, crisp and sweet. A turnip that stops and starts is woody, hot in flavor and often split. Almost everything in the care of this crop comes back to removing whatever might cause a check, rather than to feeding it heavily.
The three things that stop a turnip are drought, crowding and root damage from pests. None of them announce themselves in the leaves until several days after the damage is done, so the work is preventive: water before the plants wilt, thin before they compete, and cover the row before the beetles arrive.
Growth is quick enough that a week lost is a serious proportion of the crop. On a seven week turnip, a ten day dry spell in the middle is not a setback you recover from. It is the difference between a good root and a fibrous one.
Water steadily, and never let it swing
The classic turnip failure is a root that splits from crown to base, and it is almost always caused by heavy watering or heavy rain landing on soil that had gone dry. The root grows a firm skin while it is short of water, then the inside swells faster than the skin can stretch and the whole thing bursts.
The fix is not more water, it is more even water. Aim to keep the top four inches (10 cm) of soil damp all the way through the crop rather than swinging between soaked and bone dry. On light sandy soil in warm weather that means watering every other day; on heavier ground twice a week is usually enough.
| Condition | How often | How much | The sign you are wrong |
|---|---|---|---|
| Seedlings, first two weeks | Daily if the surface dries | A light sprinkle | Rows thinning out overnight |
| Warm weather, light soil | Every other day | Enough to wet 4 in (10 cm) | Leaves flat at midday |
| Cool weather, heavy soil | Twice a week | A thorough soak | Yellowing lower leaves, soft roots |
| After a dry spell | Little and often for three days | Build up gradually | Splits appearing across the shoulders |
If the bed has genuinely dried out, resist the urge to flood it. Water lightly for three days in a row to bring the moisture back up gradually. A single heavy soak on dry soil is what splits the roots.
Feed lightly, and stop early
Turnips are a leafy brassica that happens to be grown for its root, and they respond to nitrogen by making leaves. Overfeed and you get a magnificent bushy top with a stringy root the size of a thumb underneath, and the soft growth pulls in aphids as well.
If the bed had compost dug in for a previous crop there is often no need to feed at all. Where the soil is poor, work a light general fertilizer in before sowing and give at most one side dressing after the final thinning. Stop feeding once the root is visibly swelling; after that point extra nitrogen only coarsens it.
- Before sowing, a light base dressing Rake in a balanced general fertilizer at about 2 oz per square yard (70 g per square meter). Turnips prefer soil that was manured for the previous crop rather than freshly manured, which causes forking and hairy roots.
- Check the pH Aim for pH 6.5 to 7.0. Turnips are brassicas and acid soil both slows them and makes clubroot far more likely. Lime in the winter before sowing, never at the same time as compost or fertilizer.
- One side dressing after final thinning Scatter a small amount of general fertilizer between the rows and hoe it in. This is the only feed most crops need, and it lands at the point where the plant switches from making leaves to filling the root.
- Stop when the shoulders show Once you can see the top of the root standing proud of the soil, feeding is over. Anything added after that goes into leaf and into flavor you do not want.
Keep the row clean and the soil open
Turnips are shallow rooted and they lose to weeds badly. A row that is weedy for two weeks at the seedling stage will never catch up, because the competition arrives at exactly the point the plant should be building its first true leaves.
Hoe between the rows weekly, but keep the blade shallow and away from the plants. The feeding roots run out sideways just under the surface and a hoe driven in deep next to a turnip cuts them. Close to the plants, pull weeds by hand instead.
- Hoe shallow and often Run a hoe an inch (2.5 cm) deep between the rows once a week while the weeds are still seedlings. Weekly shallow hoeing takes a minute a row; monthly deep hoeing damages roots and does not work.
- Do not earth up the shoulders Unlike potatoes, turnips are happy with the top of the root exposed, and a green or purple shoulder is normal rather than a fault. Piling soil over the crown traps moisture against it and invites rot.
- Mulch once the plants are established A thin mulch of grass clippings or straw between the rows after the final thinning keeps the moisture even, which is the main defense against splitting. Keep it clear of the stems.
- Pull anything that bolts immediately A plant that starts to run a flower stem up will not produce a usable root. Take it out rather than leaving it, because it shades its neighbors and drops seed.
If you grow brassicas in the same bed year after year, clubroot becomes near certain. Move turnips to a bed that has not had cabbage, radish, rocket or mustard for at least three years.
Reading the plant, and what to record
The leaves tell you what is happening below ground several days before you would find it by pulling a root. Learning to read three or four signals turns turnip growing from guesswork into a routine.
| What you see | What it means | What to do |
|---|---|---|
| Wilting at midday, recovering by evening | Normal in heat | Nothing; water in the evening |
| Wilting that does not recover overnight | Root damage or serious drought | Lift one plant and look for maggots |
| Huge leaves, no root swelling | Too much nitrogen or too little light | Stop feeding, check spacing |
| Purple or blue tinged leaves | Phosphorus short, or soil too cold | Nothing in cold weather; it passes |
| Small pale leaves, slow growth | Crowded, or the soil is acid | Thin harder, check the pH |
Write down the date you did the final thinning and the date the shoulders first showed above the soil. The gap between those two dates, on your soil, tells you how much longer a later sowing needs.