Are you a Wasabi fan? Doesn't a dab of that stuff taste delicious in a tuna roll? Don't you wish you could grow the ingredients to make it home?
True wasabi – as in the stuff made from the Wasabia Japonica root — is incredibly hard to find outside of Japan. The plant is also super picky about growing conditions. In fact, to grow it in most areas, you'd need to create the perfect artificial conditions and intensively care for plants for 2 years before harvesting.
Luckily, most of us have not been eating true wasabi. That green-clay like paste that comes on your sushi plate is actually made with horseradish root (Armoracia rusticana).
Homemade wasabi is just one reason you might want to grow horseradish at home. Here are a few more.
Horseradish Plant Info:
- Hardiness Zones: 3, 4, 5, 6, 7, 8, 9
- Soil: Sandy, loam, pH between 6.0 and 7.5, deep, fertile, well-drained, work the soil with 4 to 6 inches of compost and 2 ounces of all-purpose fertilizer per square yard before planting
- Sun Exposure: Full sun to partial shade
- Planting: Plant sets 2 to 3 weeks before the average date of the last frost in spring
- Spacing: 18 to 24 inches between plants and 1 foot between rows
- Depth: 4 to 5 inches, plant at a 45 degrees angle
- Best Companions: Potato, yam, plum, rhubarb, sweet potato, grape, strawberry, asparagus
- Worst Companions: Tomato
- Watering: Water regularly, 1 to 2 inches of water per week
- Fertilizing: Apply fertilizer high in potassium and phosphorus but low in nitrogen 4 to 8 weeks after planting
- Common Problems: Brittle root, bacterial leaf spot, cercospora leaf spot, white rust, ramularia leaf spot, mosaic disease, cabbage looper, flea beetles, crucifer weevil, diamondback moth
- Harvest: Harvest when the tops have been frozen back in the fall, usually 140 to 160 days after planting
Reasons to Grow Horseradish
Horseradish root is exceptionally easy to grow, highly productive, and has a lot of other uses beyond making wasabi. It's great for clearing sinuses. It's the key ingredient in cocktail sauce. I personally couldn't imagine eating roast beef without it.
If you are a fan of the ferments, a little horseradish root adds flare to kimchi. It makes fermented mustard magical. Put a little in your homemade bread and butter pickles for a bit of bite that perfectly compliments the sweet, smooth sour flavor of those old time favorites.
In case we ever have to face another Bubonic plague, including freshly grated horseradish root in your Four Thieves Vinegar Tonic (or fire cider) will make it even more likely to ward off the illness. OK – I might be exaggerating a bit. But, in truth, the medicinal benefits of horseradish are well-known, particularly as a preventative for seasonal illnesses and a treatment for sinus congestion.
Oh, and did I mention that horseradish is one of the best all-around companion plants to ward pests away from your more precious crops?
There are only a few varieties of horseradish available for planting at home. Broadly, they are referenced by their leaf structure. There are smooth or crinkle-leafed varieties.
1. Common Horseradish
Common horseradish, sometimes called Maliner Kren, has crinkled leaves. This variety is prized for its large roots. However, it can be a bit more susceptible to some diseases.
2. Bohemian Horseradish
Bohemian horseradish has smooth leaves. There are two common commercially available strains of this variety called Swiss and Sass. The roots are not as large as common horseradish, but their disease resistance is better.
3. Crossed Horseradish
In order to improve disease resistance for commercial production, there are also some new crossed varieties of horseradish being developed. For example, Big Top Western horseradish, from the University of Illinois, has large roots and good disease resistance. However, they also have a cork-like outer layer around the root that may need to be peeled before use.
How to Plant Horseradish
Horseradish can be started from seeds or from cuttings taken from mature roots.
Method 1: Starting Horseradish from Seed
You can also direct seed, outdoors, when your soil temperature reaches 45ºF.
In either case, press seeds about 1/4 inch into your planting medium. Keep soil moist, but not soggy, until plants are well-established.
Method 2: Starting Horseradish in Pots from Root Cuttings
Seeds take a long time and are not as reliable as starting from root cuttings. Luckily, in areas with short growing seasons, you can also start new plants from root cuttings indoors.
Personally, when starting root cuttings indoors, I like to use one-gallon pots. This saves me from having to re-pot my horseradish multiple times before transplanting outside.
Fill your pot with loose potting mix. Push the root cutting 2 inches into the soil and cover. Place the crown side (usually wider) up for faster sprouting.
Keep the soil moist, but not sopping, until you are ready to plant outside.
If you plan to leave your horseradish in containers for the growing season, use large pots that are at least 18 inches deep and wide. Horseradish can grow in smaller pots, but you'll end up with stunted roots and an unhappy plant.
Method 3: Starting Horseradish in the Ground from Root Cuttings
I live in USDA planting zone 7. Since my soil warms up to about 45ºF in March or early April, I find it easiest to plant horseradish direct in the ground. Here's my procedure for direct planting when soil temperatures are between 45ºF and 75ºF.
- Root cuttings may be somewhat dehydrated after storing. Soak your cuttings in a bowl of water for a few hours before planting.
- Prepare your garden soil down to about 12 inches deep and 18 inches out from the center of your planting area. If your soil is compacted or heavy clay, add organic matter, like well-aged compost, to improve soil texture and drainage for good growth.
- Plant your root cutting at about 2-3 inches deep by laying the cutting across the soil. The head of the cutting is where leaves will emerge. So if you are planting multiple cuttings, you may want to orient the crowns in the same direction so the leaves emerge equally spaced at about three feet apart.
- Cover your root cutting with soil, level with the ground.
- Water deeply to activate growing.
- Keep the soil moist, using deep watering, until plant leaves are about a foot high.
- Weed regularly until plants are established.
Tip 1: When to Plant Horseradish
Horseradish seeds can be started indoors in early winter and planted outside after risk of frost.
Seeds can also be direct-sown in a permanent location when soil temperature is between 45ºF and 75ºF. Depending on your planting zone, this will usually be between March and mid-summer.
Root cuttings are most commonly planted in early spring or fall. This is the best time to harvest roots from existing plants to use to start new plants. Also, cooler temperatures in spring and fall facilitate speedy growth.
Tip 2: Horseradish Zone Hardiness
Horseradish is hardy for USDA planting zones 3 – 9.
As a perennial, it grows better in areas with hard winter freezes to force the plant into dormancy. It also develops better pungency in areas with long, cool growing seasons, particularly in fall.
In warm climates, consider planting in an area that will receive 6+ hours of morning sunlight and partial afternoon shade.
Tip 3: Light Requirements for Horseradish
Horseradish can be grown in full sun to partial shade. Ideally, in cool climates opt for full-sun. In warmer climates aim for morning sun and afternoon partial shade.
When starting indoors, a sunny windowsill can work or it can be grown under daylights.
Tip 4: Soil Requirements for Horseradish
When grown as a perennial, horseradish is not very picky about soil types. It can grow in almost all soil types as long as they are not water-logged. Once established it can even tolerate drought.
For best root production though, growing in deep, prepared garden soil produces bigger roots. It is also much easier to harvest horseradish grown in good soil.
Similar to other root vegetables like beets, too much nitrogen can cause the plant to focus on leaf growth rather than root growth. For best fertilization, use one of these options:
- Fertilize horseradish beds at least 6 months before you plant.
- Plant in moderately fertile soil.
- Plant after nitrogen hogs, like corn, have depleted excess nitrogen.
Tip 5: Ways to Plant Horseradish
Horseradish, for root production, is planted similar to other annual garden vegetables. Plant it in prepared garden beds in fall or early spring, then harvest in late fall.
You can also plant horseradish in a permanent location such as in an edible landscape plot as a pest deterrent and an interesting edible ornamental.
Horseradish also makes a great container plant. Use a deep and wide container to allow plenty of room for the roots to grow.
Tip 6: Expected Germination Time for Horseradish
In ideal conditions, horseradish grown from root cuttings will grow very quickly. Leaves can break ground in just a few days and be a foot tall in a month.
Horseradish grown from seed may take a few weeks to germinate. For best results, allow seedlings to grow in ideal conditions for about 10-12 weeks before hardening off and transplanting outdoors.
Tip 7: Horseradish Spacing
When grown as an annual, plant on 3-foot centers (e.g. allow 1.5 feet of space in all directions around the plant).
When grown as a perennial, due to the invasive nature of horseradish, leave a buffer between horseradish and other plants. When your horseradish begins to grow into your buffer zone, dig up new roots around the perimeter to control for size.
How to Care for Horseradish
Horseradish is fairly easy to grow. Depending on whether you are growing for annual root harvests or as a perennial companion plant, there are a few minor differences in the plant care.
Method 1: Growing Horseradish as an Annual
Technically, horseradish is a perennial. However, because the root is the edible part, many growers dig up most of the root in the fall of each year.
To replant in the same location, simply leave a section of the root behind in the soil to start next year's horseradish.
If you plan to rotate your horseradish annually for pest and disease prevention, then you can store some of your root cuttings to use to plant next year. Make sure to save roots from healthy plants that are free from defects like dark spots or streaks.
Using this method, you are technically replanting new horseradish plants each year. Similar to planting crops like garlic and winter wheat, make sure that the soil remains moist until the plant is dormant (e.g. due to winter cold). In spring, make soil is moist until the plant is growing vigorously.
Similar to growing other garden vegetables, this method depletes the soil or organic matter and minerals quickly. Apply compost annually in fall. Also, unless your soil is mineral heavy, consider applying a sprinkle of rock phosphate each year to supplement depleted minerals.
Weed regularly for best production.
Method 2: Growing Horseradish as a Perennial
Horseradish grown as a perennial is mostly used as a companion plant to deter pests away from more valuable crops such as fruit trees. However, every couple years, you will need to uproot any side growth around the main roots.
These side roots can branch off and become new plants. In time, without harvesting these runners, the plant can become invasive and hard to eradicate.
Perennial horseradish places fewer demands on the soil. Allowing the leaves to die back to the ground, and remain in place in winter, acts as a natural mulch. Adding a couple inches of mulch in fall, every other year will add back nutrients to the soil without creating nitrogen overload.
Rather than weed around perennial horseradish, consider chopping weeds down and leaving them to decompose in place under the horseradish. This adds organic matter and helps smother new weeds. Also, make sure to remove any flowering weeds or seed heads to reduce weed pressure in future years.
Possible Problems Growing Horseradish
Horseradish is relatively easy to grow with few problems. When grouping mass plantings together the risks for pest and other problems are higher.
Most home growers only need a few plants for a sufficient supply of horseradish. So, pest and disease risks are minimal on the homestead.
Those of us growing horseradish at home often grow much tastier options for the pests that might eat our horseradish leaves. Cabbage, turnip, radish, mustard, and other members of the brassica family are all preferred options for potential horseradish pests.
That being said, you may want to be on the lookout for these pests just in case.
1. Imported Cabbage Moth Larva
Those small white moths with tiny black spots on their wings, who flit around, pollinating plants with pleasure are also one of the peskiest pests for anyone growing cabbage. They lay eggs that become cabbage moth larva (aka caterpillars). The larva devours the leaves of brassicas and does severe damage to crops.
Though they aren't super likely to favor your horseradish, you may occasionally find them on your plants.
Manually picking off those larvae and feeding them to your chickens or drowning them in water is usually sufficient for control. At worst, spraying your horseradish leaves with neem oil during the mating season for those pests might be necessary.
2. Imported Crucifer Weevil
The adult Imported Crucifer Weevil is metallic blue-black and about 1/10 inch long. Their white grub-like larva bore into the horseradish roots. They impact the quantity and quality of the roots harvested.
You can use insecticides to treat for this pest. Alternatively, by growing horseradish as an annual in different locations each year, you can break up this pest's life cycle and control the pest population.
3. Horseradish Flea Beetle
Flea beetles are very small and tend to make buckeye holes in plant leaves. Except in extreme cases, they don't have much impact on the plant's productiveness. However, they do make the leaves less attractive.
If flea beetle damage covers more than 20% of the plant, insecticides may be necessary. Diatomaceous Earth, sprinkled on the leaves, can be an effective deterrent.
Alternatively, planting trap plants like radishes and turnips nearby and then using a vacuum to suck up flea beetles can work well to control populations and limit the damage.
There are a few diseases that can do severe damage to horseradish plants.
1. Turnip Mosaic Virus
Turnip Mosaic is a disease that can limit the productivity of your horseradish plant. It appears as mosaic mottling and yellow rings on the leaf.
There is no current treatment for this virus. Plant resistant varieties of horseradish if this disease is common in your area or known to be in your soil.
White rust is a fungal disease that is more likely to impact plants that are water-logged or planted too closely together. It causes discoloration in the infected parts and forms white powder pustules on the plant.
White rust can be treated with fungicides. Additionally, good soil drainage, good air circulation, and planting disease-resistant type of horseradish are good prevention measures.
3. Bacterial Leaf Spot
Bacterial Leaf Spot begins as dark green spots on leaves that eventually turn brown.
This can be controlled with fungicides and copper solutions. This disease is most common in cooler weather between 50° to 75°F. Check leaves often during cooler periods and address quickly to keep your plants productive.
Companion Planting with Horseradish
Horseradish does just fine on its own. It's one of the few plants that can be a hermit, loner-type and not shrivel up and die from loneliness. That tendency makes it a great guard plant to protect others. As such, you may want to consider planting it close to almost anything that suffers heavy pest pressure.
Best Companions for Horseradish
Here are a few ideas to get you thinking about how to use horseradish as a general pest preventative.
Horseradish is reputed for deterring the dreaded Colorado Potato Beetle. Since these are both root vegetables and benefit from similar soil types, they make good companions in terms of bed preparation too. Give horseradish plenty of root space though so it doesn't out-compete your potatoes for nutrients.
2. Plants Aphids Love
That would be any plant not in the Brassica Family that is susceptible to Aphid attacks.
Aphids are not the most destructive pest in the garden, but they can be really irritating since so many plants are susceptible hosts. Thank goodness there's horseradish to help!
Plant some horseradish in pots and move those pots near plants under aphid attack as needed. Start by using soapy water to eliminate the aphid-offenders from the infested plant. Then, let the horseradish stave off any other would-be attackers to give the affected plant time to heal.
3. Perennial Crops
Horseradish is awesome near fruit trees, with berry bushes, in strawberry patches, alongside rhubarb or asparagus. Its roots are pretty offensive to voles, moles, mice, and airborne pests. As long as it is kept in check through the regular harvesting of the roots, it makes a great general pest-preventative for long-lived perennials.
4. Long-Standing Annual Crops
Crops like sweet potatoes and pumpkins that have long growing seasons are subject to a number of different pest attacks. Planting horseradish around these plants can help deter potential pests. Also, setting container plantings of horseradish in the midst of these vining machines can deter aerial pest pressure.
Worst Companions for Horseradish
Avoid planting horseradish with any plants in the brassica family. Cabbage, turnips, kale, radish, mustard, etc. are all bad news for horseradish. Those crops stay in the ground for a few months. When they are harvested, pests may move over to your long-standing horseradish and wreak havoc.
Now for the fun part! Dig those roots up and use them for good health and delicious eating.
1. Harvesting Annual Horseradish
Horseradish tastes best after a long cool, growing period. This is why most people harvest in mid to late fall.
If you are growing horseradish as an annual, dig up the entire root. Make sure you get every last bit since even a tiny fraction of the root can return as a plant.
If you want to regrow in the same area next year, cut off a few inches of the root and leave it in the soil at 2-3 inches deep. Or, go plant it somewhere else for next year.
2. Harvesting Perennial Horseradish
OK – so you don't exactly harvest from perennial horseradish. But you do want to occasionally dig up and chop off those side shoots that give the plant the mistaken reputation for being invasive. They aren't usually so big, but you can eat those too.
When the plant is dormant but the soil is still workable, I use a spade to turn up the soil all around the main plant root. I start digging about a foot away from the crown in all directions. Then I pick out all the little root bits that my spade separated from the parent plant.
I dig down and out as far as necessary to make sure I have all those side roots. When I am satisfied, I put the soil back in place, top it off with some mulch and go have some roast beef with my horseradish tidbits!
For best long-term storage, harvest when the soil is mostly dry. Do not wash your harvested roots.
You can put them in your refrigerator crisper or store them in your appropriately humid root cellar for months.
Or, even better, you can use them fresh to make all your favorite ferments and horseradish based concoctions like wasabi, cocktail sauce, and more.
I hope this information helps you achieve that fabulous nose-clearing, horseradish happiness in your home-grown garden!