The horseradish plant may not be the most attractive member of the garden but, thanks to the distinctive flavor of its peppery root, it is a popular addition. Grown for over 3000 years the horseradish plant (Amoracia rusticiana) is part of the cruciferous vegetable family, meaning that it is distantly related to the cabbage.
A hardy perennial, these edible roots are typically defined as a vegetable. However, because of its culinary uses and medicinal benefits, it is rich in nutrients such as calcium and Vitamin C, many view the horseradish plant as a herb.
If you want to add a horseradish plant to your garden or allotment, this is your complete growing guide.
Horseradish Plant can be Invasive
Many consider the horseradish plant to be an aggressive spreader. Placed at the end of row it is a good weed barrier. Just remember to regularly curtail its growth. Growing in pots or bottomless buckets sunk into soil helps to control the root spread.
When harvesting, be sure that you remove the entire root system. Even small branches left in soil can return the following year as large roots.
Don’t place cut flowers or harvested roots on the compost heap.
Horseradish Plant Varieties
Unlike other herbs and vegetables that come in a wide range of shapes, colors and flavors there are only two types of horseradish plant: the common horseradish plant and the bohemian variety.
The common variety has broad crinkled leaves. It is considered by many to be a superior root to the bohemian type.
Bohemian varieties have narrow, smooth leaves. They are more resistant to diseases such as white rust than common varieties.
Wasabi is sometimes referred to as Japanese horseradish. While it shares the same name it is a completely different specimen, Wasabi japonica.
How to Source a Healthy Root
The horseradish plant is typically grown from root cuttings. You can also grow a new horseradish plant from fresh, healthy roots purchased from an organic food or farmers market.
If you have sourced your root from a farmers market, cut the top third of the root away, to use in the kitchen before planting the lower section.
Finally, you can grow the roots from seed but this is a slow process. Starting new specimens from roots is quicker and a lot more reliable.
Unless you are really keen on these spicy roots, one per household is plenty.
Plant your roots as soon as possible after acquiring them.
Where to Grow
A versatile specimen, these roots grow in USDA Zones 2 to 9. A durable specimen they do best in cool, moist regions. Preferring an average temperature of between 45 and 75 ℉ the roots can survive in conditions as cold as 20 ℉.
Roots are best started in the spring 4 to 6 weeks before your last predicted frost date. In warmer climates, plant in the fall. If you are growing the roots in containers, start the roots undercover in the fall before moving them outside in the spring, once all danger of frost has passed.
The horseradish plant grows best in a sunny position but they also tolerate shady positions. These specimens set long taproots, so well draining soil is ideal.
Before planting, prepare your growing site by thoroughly digging it over, removing any stones and breaking up the clumps of soil. Work in lots of organic matter or well rotted manure. In heavy soils add an ample amount of sand or compost to lighten the soil. While the horseradish plant prefers soil with a pH level of between 5.5 and 6.8 they readily grow in profiles outside this. If you are unsure what type of soil you have, a soil test kit is a quick and easy way to find out.
Dig a hole in the soil large enough to stand the root upright in. The exact depth varies depending on the size of the root, but it should be at least 2 inches deep. Hold the root upright as you fill in the hole.
Once the hole is filled in, only the top of the crown should be visible. Water well.
If you are growing more than one root, space them 18 to 20 inches apart.
You can also grow the roots in containers. This is an ideal way to control their sometimes invasive growth habit. Fill a large pot with well draining potting soil. The pot should be large enough to hold the root system, at least 2 to 3 ft deep and with drainage holes in the bottom.
Fill pots with well draining potting soil. Plant a section of root roughly 2 inches long at a 45° angle. Mulch or top dress with a multi purpose fertilizer. When applying mulches keep the crown uncovered.
After planting, sprouts emerge in the spring. The horseradish plant needs at least 1 year of continuous growth before it is ready to harvest. However, the flavor and size is better if you wait for 2 years before harvesting.
Caring for a Horseradish Plant
Once established these are low maintenance specimens that need barely any attention.
Horseradishes are believed to repel a number of common pests such as aphids, potato beetles, whiteflies, and some types of caterpillar. They also attract a number of beneficial insects such as hoverflies. This means that the horseradish plant makes a good companion for a number of fruit and vegetables, in particular yams and potatoes. Rhubarb, strawberries and asparagus also enjoy growing alongside horseradish.
Root vegetables such as potatoes benefit from being grown in close proximity to horseradish plant roots.
Once established, you need only water the soil during dry spells to help keep the foliage looking healthy. A layer of mulch around the root also helps to conserve moisture, reducing the frequency with which you need to water.
Roots growing in pots require more frequent watering than those growing in the ground.
A low maintenance addition to the garden, these roots happily grow without any amendments. If your specimens do require a little boost, add some compost to the growing bed once a month. Alternatively, you can add one cup of complete organic fertilizer per row.
Plants Setting Flowers
Sometimes established specimens set out white flowers. These are of little ornamental interest and many gardeners like to remove them to prevent the plant from wasting energy in flowering. However you can, if you wish, leave the flowers in place to attract bees and pollinators to the garden. Just remember to cut the flowers before they go to seed to prevent unwanted reseeding.
Largely insignificant, the flowers have little ornamental interest.
Dividing Established Roots
As roots mature and age they become woody. Lifting and dividing older roots helps to rejuvenate the horseradish plant. It also gives you a number of new roots to either grow on as new specimens or give away to green fingered friends.
Use a fork to loosen the soil before lifting the root from the ground. You may need to use a shovel to lift larger roots. Brush any remaining soil from the root and rinse with a hose. Allow the root to dry in the sun before preparing your cuttings.
If you only have a short growing season, plant crown cuttings. These can be made by slicing the lifted root into equal sections. Each section should have a healthy amount of roots and foliage.
In areas with a longer growing season, lift as described above before preparing root cuttings. Root cuttings are easily created by slicing the slender roots into sections, 6 to 8 inches long. Each section should have a diameter of about a quarter of an inch.
However you prepare the cuttings, plant as described above.
Growing From Seed
As I mentioned earlier you can also grow a horseradish plant from seed. A long, time consuming process many gardeners prefer to start from cuttings or by purchasing already growing roots. Either of these methods are a lot easier and more reliable than growing from seed. But if you do want to try growing from seed, this is how.
Start your seeds in position, in prepared soil. Sow the seeds half an inch deep. You can also start the seeds in biodegradable peat pots filled with fresh potting soil. As the seedling develops the pot breaks down allowing the root system to spread out. This is ideal for specimens such as the horseradish plant which develops a long taproot.
Moisten the soil and lightly cover the seeds. Place pots in a light position in a greenhouse or on a windowsill. Germination usually occurs within 15 days.
After germination, allow the seedlings to grow and develop at least one true set of leaves before thinning them out to a spacing of about 8 inches. Transplant seedlings started in pots in cultivated soil once the last frost date has passed and the seedlings have been hardened off. Starting seedlings in peat pots such as ANGTUO Peat Pots which are biodegradable means that you can transplant the seeds still in the pots into their final position.
How to Identify and Solve Common Problems
A low maintenance vegetable, horseradish is surprisingly easy to grow. A member of the brassica or cruciferous vegetable family it can suffer from common brassica issues such as cabbage white butterfly caterpillar infestations.
Flea beetles and beet leafhoppers can also target the foliage. Mulching the soil around the roots helps to prevent the pests from reaching the soil. Should you notice any signs of infestation, treat affected areas with neem oil or an insecticidal soap. Infestations of beet leafhoppers can also be treated with pesticides to prevent brittle root from developing. One of the most destructive diseases, brittle root causes leaves to shrivel and dry out.
Another common issue is bacterial leaf spot. Causing translucent spots to form on the surface of the leaf, if allowed to develop the foliage curls up and dies away. Thriving in hot conditions, keep the area around the specimen neat and tidy to help prevent the problem from developing.
Check the foliage for signs of disease or infestation.
Cercospora leaf spot causes tan colored spots with a light center to form on foliage. Affecting a number of members of the vegetable garden such as spinach and beets as the disease develops, leaves fade and fall. Lift infected specimens and destroy them to prevent the disease from spreading to other crops.
Finally, try not to overwater your roots. These specimens dislike sitting in water or wet soil. Allowing them to do so can cause root rot to develop. I find a moisture meter a really easy way to gauge how wet the soil is and whether I need to water my vegetables.The Gouevn Soil Moisture Meter provides an easy to use way to monitor the moisture content of your soil.
How to Harvest Horseradish
Young leaves can be cut as they develop. Use them in a salad for a spicy kick.
Root harvest is best done from the fall to early spring. Allowing the roots to sit in cool soil encourages the formation of the compounds that give the roots their pungent flavor. Cut back any remaining foliage to make harvesting a little easier.
Use a digging fork to make a wide circle around the plant, loosening the soil as you dig. Once the circle is complete, stick your fingers down into soil to locate the direction of the taproot.
Unlike other root vegetables horseradish taproots do not go vertically down into the soil. Instead they run horizontally below the soil surface. Follow the direction of the taproot, gently excavating the soil and exposing the root. This enables you to lift a large section of root. Simply pulling the root from soil can damage the root.
Ensure that you remove the entire root or it will probably return again next year.
Lift the root and wash any soil or dirt from it. Pat the root dry and place it in a plastic bag or an airtight container until you are ready to use. In this condition they can be stored in a refrigerator for several weeks.
Unpeeled, the roots give off little aroma. This changes as soon as you start to handle or prepare them.
Prepare your roots in a well ventilated area. The fumes they emit can irritate your eyes and make your nose run.
Peel a 3 to 4 inch section of root as you would a carrot. Cut the root into chunks and blend or dice in a food processor. Add a quarter of a cup of cold water and some crushed ice before grinding the roots into a fine texture.
Take protective measures when preparing the roots.
To make a horseradish sauce add white wine or rice-wine vinegar. For a mild flavor add vinegar either during or immediately after grinding. If you want a stronger flavor, wait a few minutes before adding the vinegar. Add 2 to 3 tablespoons of vinegar and half a teaspoon of salt per cup of grated root. Pulse the processor to finely blend your mixture. If the sauce is too wet, don’t be afraid to put it through a strainer.
Store the sauce in a clean, airtight jar such as a Kilner Jar. Stored in this condition, the sauce keeps in the refrigerator for 4 to 6 weeks.
Primarily grown for the pungent root the horseradish plant is ideal for colder climates where the cold weather enforces dormancy. Best grown in containers, where its aggressive growth habit is kept in check, this is an easy to grow, flavorsome root with numerous health benefits. When all of this is considered, it is easy to see why the horseradish plant is an increasingly popular addition to the garden.
Jen is a master gardener, interior designer and home improvement expert. She has completed many home improvement, decor and remodeling projects with her family over the past 10 years on their 4,500 sf Victorian house. She is also a passionate farmer who keeps goats, chickens, turkeys cows and pigs on her farm, and an instructor for her community’s Organic and Sustainable Farming project.