Turnip

Light and exposure

The turnip likes sun without needing to be baked all day long. A sunny to lightly shaded spot suits it, which is handy for summer sowings where a bit of shade during the hottest hours keeps the soil from drying out. In spring, give it full sun instead for brisk growth.

Since it grows fast and holds the ground only briefly, the turnip slips easily between two longer crops or after an early harvest of peas or lettuce. It benefits from an open position with good air flow, which limits standing moisture on the foliage and therefore disease.

Watering

Regular watering is the key to a good turnip. Soil that stays cool gives tender, sweet, juicy roots. As soon as the ground dries out, the plant is stressed, which makes the turnip pungent, fibrous, sometimes hollow at the core. Sudden swings are the worst of all: a dry spell followed by heavy watering causes the roots to split.

So aim for steady moisture, with regular watering during dry spells, especially for the late-summer sowings, when the soil is still warm. A light mulch between the rows helps keep things cool. In soil kept cool, the turnip’s fast growth does the rest and the root stays sweet.

Soil and repotting

The turnip prefers loose, cool soil that has not been manured too recently. Light ground, worked deeply, lets the root form without obstacle and without distortion. Heavy, compact soils give twisted turnips, so it is better to lighten them with well rotted compost and good digging.

Avoid fresh manure just before sowing, as it encourages forked roots and lush foliage at the expense of the turnip itself. A neutral to slightly acid pH suits it. Like all brassicas, the turnip appreciates soil that is not short of calcium, which calcareous and clay-limestone ground supplies naturally; on acid soil a liming amendment fills the gap and hampers clubroot along the way.

Temperature and humidity

The turnip is a cool-climate vegetable, and it is heat, not cold, that limits it. It germinates and grows best between 10 and 20 degrees. The strong heat of high summer does not suit it: it makes the roots pungent and sometimes pushes the plant to run to seed instead of forming its turnip.

It is a vegetable that tolerates cold, and even seeks it out for the autumn varieties. Winter turnips hold in the ground until the frosts, and a light frost even sweetens their taste by turning part of the starch into sugars. Late summer sowings take advantage of the cool nights of the late season to form firm, sweet roots.

Pruning and upkeep

The turnip is not pruned, but one action is crucial: thinning. After emergence, when the seedlings have two or three true leaves, remove the weakest to keep only one turnip every 10 to 15 centimetres. Without this room, the roots stay tiny and compete with one another, each no bigger than a radish.

Thinning in two stages is better still: a first pass fairly early, a second one or two weeks later, eating the young plants you pull out, leaves included, which cook like spinach. Hoe regularly between the rows to keep weeds at bay, as the turnip dislikes competition.

Pests and diseases

The turnip’s main enemy in the garden is the flea beetle, that small black jumping beetle that riddles young leaves with many little round holes. On plants that have just emerged, a heavy attack can seriously slow the crop. It strikes mostly in hot, dry weather, hence the value of keeping the soil cool and putting an insect-proof mesh over young sowings.

The cabbage root fly lays at the collar and its larvae attack the root, making it maggoty. A protective net laid at sowing is the most effective defence. Like all brassicas, the turnip is also prone to clubroot in acid, wet soils: avoid growing cabbages and turnips in the same spot year after year, as rotation is your best ally.

Propagation

The turnip is grown from seed, and always directly in place, because its root does not tolerate transplanting. Sow thinly in rows 25 to 30 centimetres apart, one centimetre deep, in fine, cool soil. Emergence is fast, often within a few days in mild weather, which makes the turnip an excellent vegetable for reassurance when you are starting out.

Stagger the sowings every two to three weeks to spread the harvest rather than picking everything at once. To produce your own seed, you would need to let a few plants overwinter and flower the following year, but the turnip crosses easily with other brassicas, which makes selection tricky in the amateur garden.

Month-by-month care calendar

Green Hub tips

• Always sow in place and thin without regret: a crowded turnip stays no bigger than a radish.
• Never stop watering. A thirsty turnip turns pungent, tough or hollow, so keep the soil cool, above all during the late-summer sowings.
• The real window is late summer. Sowings made ten to twelve weeks before the first frosts give the autumn and winter turnips that keep.
• Lay an insect-proof mesh at sowing: it heads off the flea beetles that hole the leaves and the cabbage root fly.
• A light autumn frost sweetens winter turnips: do not rush to pull everything up before the first cold snaps.