At a glance
- You propagate horseradish from thongs, that is pencil-thick side roots, which you plant at an angle in spring from March to April (CW 10 to 16).
- It runs. Every root fragment left in the ground sprouts anew, so it belongs in a root barrier or a large tub.
- The spot should be deep, loose and rich in humus, plus full sun. The taproot will not tolerate waterlogging.
- Harvest comes after the first frost, from late October (CW 44) into winter. Cold makes the root milder and better for storage.
- A single clump feeds a family for years. Two plants are already too many for most gardens.
There are few garden plants where the hardest part is not getting them to grow, but getting them to stop. Horseradish (Armoracia rusticana) is one of them. Plant a thumb-length piece of root into a loosened bed in spring, and by autumn you have an arm-thick taproot and foliage that rivals a small rhubarb. Plant it in the wrong place, and you will still have it three years later, even though you were sure you had long dug it out. That very vigour makes it one of the most rewarding and at the same time most headstrong plants in the vegetable garden. Plan for it from the start, and you harvest pungent roots for years without the horseradish taking over half the bed.
Why horseradish is both treasure and menace
Horseradish is a perennial from the cabbage family (Brassicaceae), related to cabbage, mustard and radish. Its heat comes from mustard oil glycosides that are only released when the cells are damaged during grating. In the kitchen it has been at home for generations: with boiled beef, with smoked fish, as creamed horseradish for the Sunday roast. In Bavaria and Austria it is simply called Kren, and everyone there knows that a single bed of it is enough to supply the whole extended family.
The problem is the very reason it is so reliable. Horseradish spreads through root runners, and every fragment in the soil is a new plant. Dig out a root in autumn and leave even a finger-length remnant behind, and it sprouts again the next spring. That is why it is treated as half a nuisance in many old gardens. Yet it is not a weed but a crop plant that simply needs to be firmly contained. The trick lies not in fighting it, but in the right place.
Because it is a true brassica, the same crop-rotation rule applies to horseradish as to cabbage: keep about a four-year break and do not plant it directly after potatoes, radishes or mustard. The large, juicy leaves also draw cabbage whites and flea beetles. For the root that is usually harmless, since a sturdy clump easily shrugs off a bit of feeding on the foliage.
Planting thongs: how to propagate horseradish
The classic route to your own horseradish is thongs, that is root cuttings. You get them from an existing plant, from the allotment club, or as ready cuttings from a specialist supplier. Planting happens from early April to early May (CW 10 to 16), as soon as the soil has dried out and is easy to work.
Cut the thong
Cut pencil-thick side roots from a mother root, ideally 20 to 30 cm long and 1 to 2 cm thick. Cut the top end straight and the bottom end at an angle. That way you will not mix up the direction when planting.
Loosen the bed deeply
Loosen the soil 40 to 50 cm deep. Only in truly loose earth does the root grow straight and thick. If it hits stone or compaction it branches out and turns crooked.
Set it at an angle
Lay the thong at roughly a 45 degree angle: the straight top end just 5 cm below the surface, the angled bottom end around 15 cm deep. This slant drives the plant's energy into the thickness of the taproot.
Keep your spacing
Set the thongs at least 50 cm apart. Horseradish needs room, and crowded rows give only thin roots. For home use one or two plants are plenty.
Water in and be patient
Water thoroughly once and keep the soil evenly moist for the first few weeks. The first leaf often does not appear until three to four weeks later. Until then the root is working unseen below the soil.
If you want especially smooth, thick roots, carefully expose the clump once in midsummer and strip off the fine side rootlets on the upper third (this is called lifting). The plant then puts its energy into the single main root rather than into many thin offshoots. Earth it up again afterwards and water in.
What horseradish needs from its spot
Horseradish is a heavy feeder, but no diva. It thrives on almost any soil; only the quality of the root is decided by the location. The deeper and looser the earth, the straighter and thicker the harvest.
- Deep, loose soil
Sandy loam is best, loosened 40 to 50 cm deep. Break up heavy clay soils before planting with coarse sand and mature compost. A pH of 6.0 to 7.5 suits it well.
- Full sun
At least six hours of direct sun a day. It will grow in part shade, but stays weaker and forms less root mass.
- Evenly moist, never wet
Its water need is moderate. The soil should stay moist but drain well. Waterlogging rots the taproot, a real risk on heavy soils in particular.
- Feed sparingly
Work mature compost in shallowly in spring, top up in early summer if needed. Too much nitrogen drives the foliage at the expense of the root, and the root is what you want to harvest.
The root barrier: keeping horseradish in check
This is where it is decided whether horseradish becomes a blessing or a years-long battle. Because every root fragment sprouts anew, you need a physical boundary. The principle is the same as with mint or bamboo: the root zone is sealed off downwards and sideways so the runners cannot eat their way into the rest of the bed.
The simplest approach is to plant horseradish in a bottomless tub or an old mortar bucket with holes, which you sink into the earth up to the rim. A diameter of 40 cm and 40 cm of depth are enough for a strong root. Alternatively, install a rhizome barrier from the bamboo trade: a tear-proof band that you sink vertically 60 cm deep around the planting spot. It is important that the rim sticks up a few centimetres above the soil, otherwise the runners simply travel over the top.
The third and most honest method is the annual full harvest. In autumn you simply dig out the whole plant, take the thick main root for the kitchen, and plant a thong as the next generation. That way no old stock stays in the ground to spread. This is exactly how many old allotments have done it for generations, entirely without a plastic barrier.
Horseradish you plant once and harvest for a lifetime. You just have to know where.
Allotment gardener's wisdom
Care through the year
Once the horseradish has settled in, it asks for little. In spring it reliably sprouts anew from the overwintering root; the foliage dies back in autumn. Keep the area weed-free while the leaves are still small. Later the large leaves shade the soil themselves and keep weeds in check.
Watch out in early summer for flea beetles and cabbage white caterpillars, which tear round holes and ragged feeding damage into the leaves. A healthy, well-watered clump tolerates this. But if the foliage is stripped bare over large areas, a fine-mesh insect net helps, laid directly after sprouting, before the butterflies lay their eggs.
Runners that appear despite the barrier should be dug out deeply the moment you see them. The earlier the easier, because a young shoot has not yet formed a thick root. Do this a few times a year and you will keep the horseradish in check with ease.
Harvesting after the frost
Horseradish is harvested when the foliage has died back, that is after the first hard frost from late October (CW 44) into winter. This is no coincidence: the cold converts starch into sugar and makes the root milder and more aromatic. Harvested too early it often tastes coarse and harshly biting.
For horseradish, frost is a friend, not a foe. The plant is fully hardy down to about minus 20 degrees and stays in the ground without trouble. You can dig up the roots as needed all winter, as long as the soil is not frozen rock-hard. A bale of leaves or straw over the bed keeps it diggable for longer.
To harvest, cut in deeply all around with the spade and lever out the taproot carefully, as whole as possible. Every piece that breaks off and stays in the soil is the start of the next plant. For propagation, cut off the pencil-thick side roots as thongs right away, bed them down lying in moist sand, and store them cool and frost-free in the cellar until spring.
Armoracia rusticana
- Familie
- Cabbage family (Brassicaceae)
- Standort
- Full sun, deep and loose
- Saison
- Plant thongs CW 10 to 16 · harvest from CW 44
- Wasserbedarf
- Moderate, no waterlogging
- Frosthärte
- Fully hardy to about -20 °C
Processing and storing
Freshly grated horseradish develops its full heat within seconds and fades just as quickly. So grate it only just before serving, ideally by an open window, because the fumes bring tears to your eyes. A splash of vinegar or lemon right afterwards fixes the heat and keeps the grated mass from turning brown.
Whole roots keep for several weeks in the vegetable drawer of the fridge, wrapped in a damp cloth. For a winter store, bed them down like the thongs in moist sand in a box in the cool cellar, much the way you would keep carrots and beets in the classic sand box or earth clamp. Grated horseradish also freezes well in portions and keeps a good part of its heat that way.
Frequently asked questions about horseradish
Frequently asked questions about horseradish
How do I get rid of horseradish once it has spread?
It takes patience rather than chemicals. Dig the area over as deeply as possible in autumn or spring and pick out every root fragment, even the fine ones. Because every remnant produces a new shoot, you then have to dig out each emerging sprout deeply in the following months. After one or two seasons of consistently removing every sprout, the root exhausts itself and the stand gives up.
Can I grow horseradish in a tub or pot?
Yes, and for small gardens or the balcony it is even the smartest solution, because the pot limits the runners by itself. Take a tall container at least 40 cm deep and wide so the taproot has room. Drainage holes against waterlogging are essential. In winter place the tub sheltered against the house wall and wrap it against freezing through.
Why is my horseradish root thin and branched instead of thick?
Usually it comes down to the soil or the spot. A thick, straight taproot only forms in deeply loosened, stone-free earth. If the root hits compaction or stones, it branches. Crowded spacing, too much nitrogen or too little sun also drive the plant into foliage rather than root. Setting the thongs at an angle and the midsummer lifting also help towards a smooth main root.
When do you plant thongs and when do you harvest horseradish?
Planting happens in spring, from roughly early April to early May (CW 10 to 16), as soon as the soil has dried out. Harvest comes after the first frost, from late October (CW 44) into winter, because the cold makes the root milder and more aromatic. Hardy as it is, you can dig it up as needed throughout the cold half of the year.
Is horseradish perennial and how often do I need to replant?
Horseradish is a perennial and sprouts each spring from the same root. So you do not need to replant every year. Many gardeners nonetheless harvest the whole plant in autumn and set a fresh thong: that keeps the root young and thick, and no old stock stays in the ground to spread uncontrolled.
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