Horseradish

Horseradish: how do you recognise it?

Habit

Clump of large, upright leaves, with flower stems up to 80 cm tall and 50 cm wide.

Leaves

Large, oblong and glossy green with a wavy, toothed edge, up to 60 cm long. The first leaves in spring are sometimes deeply cut.

Flower

Small white four-petalled flowers in loose sprays, in May–June.

Root

Thick, white, fleshy taproot with light brown skin, 20–30 cm long and 2–5 cm thick, with many side roots.

Flavour

Hot and pungent when grated raw; the heat only develops when the root is damaged and fades with long cooking.

Flowering: May–June · Harvest and fruit: October–March · Plants: March–April

Why grow it?

• Fresh, fiery root to grate yourself, far hotter than anything from a jar.
• Undemanding: grows in sun or partial shade in almost any soil.
• Harvest from autumn to spring, just when the garden has little fresh to offer.
• The white flowers in May–June attract bees.
• One or two plants give enough root for a family.

Horseradish: where does it grow best?

• Sun or partial shade; the roots grow thickest in sun.
• Deeply dug, fertile soil: sand, loam or clay, slightly acid to chalky. In hard, stony soil the roots fork and twist.
• Ordinary to moist soil; in long droughts the roots turn woody.
• Give it a permanent corner of the vegetable garden or a large sunken container, with 40–50 cm between plants.

Light

Sun and partial shade

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Normal or wet

Size

0.8 m tall, 0.5 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Rhubarb: Another stayer for a permanent corner of the vegetable garden.
• Lovage: A second large kitchen herb that stays in the same spot for years.
• Pot marigold: Brightens the corner and attracts pollinators.
• Chives: Small and perennial, for the edge of the same corner.

Horseradish: when and how to plant it?

Plant in March–April.

1. In March–April, plant a piece of root (a thong) 20–30 cm long and about as thick as a pencil.
2. Dig the soil deeply and work in compost or well-rotted manure.
3. To stop it spreading, plant it in a large container at least 50 cm deep, sunk into the ground up to its rim.
4. Set the thong in at an angle, thick end up, with the top about 5 cm below the surface.
5. Leave 40–50 cm between thongs and mark the spot.
6. Water in and keep the soil moist until the first leaves appear.

Care

Watering

Water thoroughly in long dry spells, or the root becomes woody.

Feeding

A layer of compost in spring. Too much nitrogen mainly gives leaves.

Harvesting

From October–November, when the leaves die down: lift the roots completely. Small amounts can be dug all winter whenever the ground is not frozen.

Storing

Lifted roots keep for months in damp sand in a cool place, or for a few weeks in a bag in the fridge.

In the kitchen

Grate the root just before use and mix it straight away with a little vinegar or lemon juice to keep it white and hot. Delicious with smoked fish, beef, sausages and in sauces.

Tip: Replant fresh, straight thongs every spring and lift everything in autumn: you will get thick, clean roots instead of a tangle of thin ones. Grate it outdoors or by an open window, as the fumes sting the eyes and nose.

Horseradish: when to prune it?

When: Horseradish is not pruned. Simply clear away the dead leaves in autumn.

How:

• Remove yellow and dead leaves in autumn; they can go on the compost heap.
• Leave the flower stems for the bees, or cut them off after flowering if you want a tidier plant.
• Dig out any new shoots outside the container or their corner straight away, roots and all.

Caution: Do not chop up an unwanted plant with a spade: every piece of root will regrow. Dig everything out carefully.

Pruning calendar and basic rules

Propagation

Root cuttings

When harvesting in autumn or winter: keep straight side roots 20–30 cm long in damp sand and plant them in March–April. Cut the top straight and the bottom at a slant so you know which way up they go.

Division

In spring, slice off a piece of the clump with root and bud using a spade and replant it elsewhere.

Horseradish: how does it get through the winter?

Hardy to −30 °C.

• Very hardy, to about −30 °C: it never needs protection.
• The leaves die back in autumn; the roots can simply stay in the ground.
• In hard frost the ground is too firm to dig: lift a supply in advance and keep it in damp sand.

Diseases and pests

• Flea beetles: Small holes in young leaves in spring. Keeping the soil moist and covering young plants with insect mesh helps.
• Caterpillars: Cabbage white caterpillars eat the leaves in summer. Pick them off; a healthy plant recovers by itself.
• White blister: White pustules on the undersides of the leaves. Remove affected leaves and clear dead foliage in autumn.
• Forked roots: Thin, twisted roots in hard or stony soil. Dig deeply and replant fresh, straight thongs every spring.
• Spreading: New plants everywhere after digging or rotavating. Dig them out roots and all, and plant in a sunken container from now on.

Through the year

• January: Harvest when the ground is not frozen.
• February: Harvest. Keep side roots as cuttings in damp sand.
• March: Plant root cuttings.
• April: Planting. Add compost.
• May: Flowering. Watch for flea beetles.
• June: Flowering. Water in dry weather.
• July: Water in dry weather. Remove shoots outside the container.
• August: Water in dry weather.
• October: The leaves die back. First roots to harvest.
• November: Harvest. Clear away dead leaves.
• December: Harvest as needed.

Edible and useful

Roots (October–March)

Lift the roots from October to March, once the leaves have died down, when they are at their hottest. Dig up a piece of root and leave the rest, or replant a piece with a crown. Raw and grated, horseradish is fiercely hot because of a mustard oil that is only released when it is grated; heat makes it mild. With roast beef, smoked fish, sausages, in sauces and in a beetroot salad.

Storing

Unpeeled roots keep for weeks in the fridge in a plastic bag, or all winter in a box of damp sand in a cool cellar. Grated horseradish keeps for a few weeks in the fridge in a closed jar with a little vinegar and salt; without vinegar it quickly turns brown and bitter.

Caution: Grate horseradish outdoors or by an open window: the fumes sting the eyes and nose sharply. Do not give it to young children, and do not eat too much with stomach ulcers or kidney problems. Horseradish spreads: every bit of root left in the ground grows again. Grow it in a large pot or a contained corner.

Eating and using is at your own risk: see the terms of use.

Recipes

• Creamy horseradish sauce (Other · ± 250 ml · 15 min)
• Beetroot salad with horseradish (Dish · 4 people · 15 min + 1 hr)

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• The heat only develops when you grate or cut the root: substances from the cells then turn into a pungent mustard oil.
• Outside Japan, what is sold as wasabi is often mostly horseradish with green colouring.
• In our climate horseradish rarely sets viable seed: it is almost always propagated from pieces of root.