Vegetable · Brassicaceae
Horseradish
Armoracia rusticana
Tuck one root into deep, loose soil and this forgiving perennial gives back fiery harvests every fall.
Full sun
Every 7–10 days
140–180 days
USDA 3–9
Overview
Horseradish earns its spot in the garden for one wonderful reason: the pungent root you grate into sauces and dressings. It sits in the mustard family right beside cabbage and kale, so it carries those same lively mustard oils. Leave it in the ground and it returns faithfully each year as a hardy perennial, shaking off cold that would finish off most crops.
If you're new to growing, this is a kind plant to start with. Press a piece of root into good soil come spring, offer it sun and water, and it takes off fast without asking much of you. Your real job isn't keeping it alive, it's keeping it where you planted it, since horseradish loves to wander.
Bite into the raw root and at first there's almost nothing, then comes a warm rush of heat that clears the sinuses. That fire waits quietly in the cells until you grate or chew the root, which is just why a sauce you make fresh tastes so much livelier than one from a jar.
Care
The short version: give it full sun and deep, loose, fertile soil, with about an inch of water a week for the smoothest roots. Go easy on the nitrogen, pull off the flower stalks, and settle the plant into its own bed so it can't roam, and you'll do just fine.
Light
Horseradish is happiest in full sun, which drives the strongest root growth. It will take a little afternoon shade and still give you something, just a milder, smaller root, so don't fret if your spot isn't perfect.
Water
Offer about 1 inch of water a week and your roots come up larger and smoother. Once it has settled in, the plant handles dry spells with ease, so steady moisture is a bonus for a good crop rather than a demand you have to meet.
Soil
The root grows straightest in deep, loose, fertile loam with plenty of organic matter. Aim for a pH between 6.0 and 7.5, and loosen the bed deeply before planting so the taproot has a clear, easy path down.
Temperature
This is a truly cold-hardy plant, taking winter lows all the way down to about -31°F (-35°C) and brushing off frost. It grows through the warm months up to roughly 86°F (30°C), and a hard fall freeze only makes the flavor sharper.
Humidity
Everyday outdoor air suits it perfectly, somewhere around 40% to 70% humidity, with nothing for you to adjust. Horseradish is far too tough to ever fuss over the moisture in the air.
Feeding
Work a balanced fertilizer or a little compost into the bed at planting and that's usually all it needs. A light hand pays off, since too much nitrogen pushes leafy top growth and leaves you with forked, branchy roots.
Pruning
Snap off the flower stalks as they show up so the plant pours its energy into the root instead of blooming. In late spring some growers also rub off the upper side shoots, a friendly trick called suckering that coaxes one fat taproot instead of a cluster of thin ones.
Repotting
Horseradish isn't really a container plant, so no need to worry about pots. If you keep it in a confined bed, lift and replant fresh root sets each year to keep the crop vigorous and nicely in bounds.
Size & spacing
Plants reach 24 to 35 inches (60 to 90 cm) tall with a leafy spread of 12 to 24 inches (30 to 60 cm). Give each one a little room and a bed of its own, and it can grow happily without crowding its neighbors.
When to plant
Horseradish loves the cold, and that works in your favor. Set the root sets out in early spring the moment the ground can be worked, let them fill out all season, and dig the roots in late fall after the first frosts, when the flavor turns its sharpest.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Plant root cuttings (sets) at a 45-degree angle in early spring, 4 to 6 weeks before the last frost as soon as soil can be worked.
- Harvest: Harvest roots in late fall after the first frosts; flavor is sharpest after cold weather. Roots can also be dug in early spring before new growth.
Hardiness
USDA hardiness zones: 3–9
Temperature: down to -40°C
Troubleshooting
Horseradish asks very little of you, and the few things that go sideways almost always show up in the root or in where the plant chooses to grow. Find what matches below and step in early, and take heart, because a little care at planting quietly heads off most of it.
Fresh shoots popping up where you already harvested
This one catches every new grower off guard, so you're in good company: horseradish resprouts from the tiniest scrap of root, and one harvest can quietly become a bed-wide comeback. Dig out every piece you can find, keep gently pulling the regrowth, and the buried root will run out of steam in time. If you plant it inside a buried barrier from the start, you skip the whole struggle.
Fix:
- Dig out as much root as possible
- Repeatedly remove regrowth to exhaust the root reserves
- Confine plantings to a contained bed or buried barrier
Roots come up forked or knobby instead of one clean taproot
Don't take a lumpy root personally. It usually means the soil was compacted, rocky, or shallow, so the taproot split as it pushed down, and too much nitrogen or a skipped side-shoot rub can do the same. Loosen the bed deeply next time, go lighter on the nitrogen, and strip those upper side roots once in early summer, and you'll be rewarded with straighter roots.
Fix:
- Loosen and deeply till soil before planting
- Remove side shoots from the upper portion of the root in early summer
- Reduce high-nitrogen feeding
Little holes dotting the leaves
Try not to worry when you spot those tiny shot-holes, because they are almost always flea beetles at work, with cabbageworms and diamondback caterpillars taking the bigger bites. A floating row cover over young plants, a quick handpick of any caterpillars, and a little Bt if things slip past you will settle it. Best of all, the leaves can look chewed and the roots will still come in just fine.
Fix:
- Use floating row covers on young plants
- Handpick caterpillars
- Apply Bacillus thuringiensis for caterpillars if needed
Toxicity
People enjoy the grated root with no trouble at all, and that pleasure is the whole reason to grow it. For animals the picture changes: the very same sharp mustard oils that give horseradish its kick will irritate the mouth and gut of cats, dogs, horses, and other pets. It won't poison them, but a mouthful brings real discomfort, so keep roots and trimmings tucked out of their reach and everyone stays happy.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Mild
A cat that takes a bite of the pungent root may start to drool, paw at its mouth, and turn away from food for a little while. Those sharp mustard oils sting the mouth and can leave the tummy unsettled, but it settles on its own.
Dogs Mild
A dog is the pet most likely to unearth and chew a root, and the mustard-oil burn tends to bring on drooling, vomiting, or loose stools. It usually clears up by itself, though a big mouthful is worth a quick call to your vet just for peace of mind.
Horses Mild
Horses hardly ever bother with the harsh leaves, but one curious bite can irritate the mouth and gut and leave a horse off its feed. Keeping the plant out of a grazing animal's reach spares them the discomfort.
Rabbits Mild
The fiery isothiocyanates are simply too harsh for a rabbit's delicate digestion, so even a small nibble can upset its gut. This is one green you'll want to keep off the menu for them.
Livestock Mild
Cattle, sheep, and goats almost always graze right around the peppery foliage, but any that do take a mouthful may show mouth and stomach irritation. Fencing horseradish off from pasture keeps everyone comfortable.
Birds Mild
Backyard poultry usually leave the sharp leaves well alone, and a stray peck mostly just irritates the crop and gut. It helps to keep trimmings away from where birds forage.
People Edible root safe
The grated root is a beloved kitchen staple, safe to eat and prized for its bright bite. The fumes can sting the eyes and nose while you work, so grate in a well-aired spot and keep it away from your face.
Grating or processing the fresh root releases sharp volatile mustard oils that irritate the eyes, skin, nose, and mouth; work in a ventilated area and avoid touching the face. The plant is not on ASPCA headline toxic lists but is an irritant.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
United Kingdom
Animal PoisonLine: 01202 509000 (fee applies)
Australia
Animal Poisons Helpline: 1300 869 738
Varieties
Only a handful of horseradish types are grown, split between the ones raised for the kitchen and one grown purely for its leaves. These are the names you're likely to meet.
Common (Bohemian)
You'll find this narrow, smooth-leaved type shrugs off most disease with ease, and it simply gives you a little less than the broad-leaved kinds.
Maliner Kren (Big Top)
Broad, dark, crinkled leaves rise above strong, high-quality roots, and this reliable one holds its own against disease.
Variegata
Chosen for its pretty white-marbled, variegated foliage, this one earns its place for looks rather than the kitchen.
How to propagate
You won't be starting horseradish from seed, and that's part of the fun. It multiplies from pieces of its own root, which is one reason a single planting can keep you supplied for years.
DivisionEasy
Early spring (or fall lifting for spring planting) · One growing season; roots are usually harvestable the first autumn after spring planting.
Good news for a first try: horseradish grows from root cuttings, not seed, so there's nothing finicky to nurse along. Take pencil-thick sets 8 to 14 inches long, set them in early spring at a 45-degree angle with the wide crown end pointing up, or just divide a crown you already have. Plant in spring and you can dig your very first roots that same autumn.
Myths
Horseradish is just a milder relative of the radish.
The sharp bite is really all these two share. Horseradish is a perennial in the mustard family, and its heat only wakes up as isothiocyanates when the cells are crushed. It is a completely different plant from the radish.
Once you plant horseradish you can easily pull it out later.
Pulling it out is the tricky part, so plan ahead and you'll be glad you did. Any scrap of root left behind will sprout again, which means the plant settles in and spreads for years. Grow it inside a buried barrier and you can reclaim that bed whenever you like.