Beetroot Care: Watering, Feeding and Keeping Roots Tender

Steady water is the whole job

Beetroot swells its root in response to consistent moisture, and it records every interruption. A dry fortnight followed by a soaking produces roots with tough concentric rings, a woody core, or a lengthways split. Unlike a leaf crop, the damage is permanent: you cannot water a woody beetroot back into tenderness.

In practice that means about an inch (25 mm) of water a week, delivered in one or two goes rather than a daily sprinkle. A light daily watering keeps only the top inch of soil damp and encourages shallow roots. Push a finger in to the second knuckle: if it is dry at that depth, water thoroughly.

The most sensitive period is from the point the roots begin to swell, roughly six weeks after sowing, through to harvest. Before that the plant is making leaves and is fairly forgiving. After swelling starts, a dry spell costs you quality that you will taste.

A mulch of straw or compost an inch deep between the rows does more for beetroot quality than any amount of extra watering. It narrows the swing between wet and dry, which is exactly what the crop is reacting to.

Feed for roots, not leaves

The classic beetroot failure is a magnificent stand of dark glossy leaves sitting over roots the size of a marble. That is nitrogen. Beetroot on freshly manured ground, or given a high nitrogen feed, will put everything into foliage and delay swelling until it runs out of season.

Grow it on ground that was manured for a previous crop instead. If the bed genuinely needs feeding, use something with more potassium than nitrogen, worked in before sowing rather than dribbled on later. A dressing of wood ash or a general fertilizer at half the recommended rate is usually plenty.

Beetroot is one of the few garden vegetables that actively likes a little salt, being descended from a coastal plant. It also tolerates a higher pH than most roots and does poorly on acid soil. If the bed is below pH 6.0, lime it in the season before you sow, not on the day.

Boron and the hollow black center

If you cut a beetroot open and find black, corky patches in the center, or the crown has sunken brown pits on the surface, that is boron deficiency and not a disease. Beetroot is unusually hungry for boron and shows it first among garden crops. It appears most on light sandy soils, on ground that has been heavily limed, and in dry seasons, because boron only moves to the roots dissolved in water.

The fix in a dry season is often just water rather than boron: keep the soil evenly damp and the boron already present becomes available. If it recurs year after year on the same ground, a very dilute borax solution watered on before sowing corrects it, but the margin between enough and toxic is narrow, so measure rather than guess.

1. Check the pH before you blame boron Over-liming locks boron up. If you have limed heavily in the last two seasons, that is the more likely cause than a shortage in the soil.
2. Keep the bed evenly moist Boron reaches the root in the soil water. A crop that dries out repeatedly can show deficiency in soil that has plenty of it.
3. Correct at a measured rate, once If it is a genuine deficiency, apply a dilute borax drench to the bed before sowing, once in the season. Never top it up mid season and never apply it twice to the same ground in a year.
4. Add organic matter over time Compost holds boron and releases it steadily. On light sandy ground this is the durable answer rather than a chemical correction each year.

Weeding, and why you do it by hand

Beetroot roots sit shallow, with the top third of the root actually above soil level and the feeding roots spreading sideways just under the surface. A hoe run close to the row cuts them. Weed within four inches (10 cm) of the plants by hand, and reserve the hoe for the middle of the paths.

Weed competition matters most in the first six weeks. After that the leaf canopy closes over and shades the ground for itself. Getting the bed clean early, then mulching, means you can more or less leave it alone through the swelling period, which is also when you least want to be disturbing the soil.

Do not draw soil up over the shoulders of beetroot the way you would with carrots. The exposed shoulder is normal and harmless, and burying it encourages rot at the crown.

Do not strip the leaves

Beetroot leaves are genuinely worth eating, and it is tempting to keep cutting from the plants while the roots grow. Within limits this works, but the root swells on what the leaves make, so every leaf you take is size you do not get.

The working rule is to take no more than a third of the foliage from any plant, always the outer leaves, and never the small cluster at the center of the crown. Cut cleanly at the base with scissors rather than tearing, because a torn leaf stalk leaves an open wound at the crown that rots. If you want a serious quantity of leaves, grow a few plants at close spacing purely for cutting and let the rest make roots undisturbed.

1. Take the outer leaves only Work from the outside in. The center of the crown is the growing point and stripping it stops the plant for a fortnight.
2. Stop at a third Leave at least two thirds of the foliage on the plant at any time. Beyond that you are trading root size for salad.
3. Cut, do not tear Snip the stalk an inch above the crown with scissors. Tearing pulls a strip of skin off the crown and lets in rot.
4. Give heavily picked plants a rest If you have cut hard for a meal, leave that plant alone for two to three weeks. Repeated cutting from the same few plants is what produces tiny roots.

What to record while it grows

Note the date the roots first became visible at the surface, and the dates of any dry spell longer than ten days. When you eventually cut a root open and find hard rings, those two entries tell you exactly which week caused it. Record what you fed the bed and when, alongside the eventual root size, and after two seasons you will know your own ground's nitrogen level better than any general guidance can tell you.