Horseradish is a perennial vegetable or herb that is primarily grown for its pungent roots. This is the same horseradish that most people buy in a jar and use to spice up a variety of dishes, from roast beef to cocktail sauce, and to complete a Passover Seder plate. Horseradish leaves can also be eaten when they are young and tender, but they should not be eaten by animals because they are mildly toxic.
Horseradish (Armoracia rusticana) is a clump-forming perennial plant in the Brassicaceae family. It is grown from root divisions and can be extremely aggressive. If you worry about horseradish spreading and taking over your garden, you can plant it within barriers or you can grow it in a container, where you have the option of growing it as an annual plant with a single large root.
|Botanical Name||Armoracia rusticana|
|Common Name||Horseradish, red cole, German mustard|
|Plant Type||Perennial herb|
|Mature Size||12 to 18 inches tall and 15 to 18 inches wide|
|Exposure||Full sun to part sun|
|Soil Type||Loose, rich soil|
|Soil pH||Neutral (6.0 to 7.5)|
|Hardiness Zones||3 to 9|
|Native Area||Central Europe|
How to Grow Horseradish
Horseradish has long taproots, so well-prepared soil is important. Prepare the garden bed by turning in a couple of inches of organic matter. A prepared bed is very important when growing plants as perennials because you won't be able to correct your mistakes later.
Grow new horseradish plants with pieces of root that are about the diameter of a finger and 12 to 18 inches long. It will spread, so you won't need more than one or two plants to feed the whole family. Dig holes about 6 to 8 inches deep and 12 inches apart. Plant one root per hole at a 45-degree angle with the crown, or large end, toward the top at the soil line, and the small end at the base of the hole. Backfill the hole to cover the crown of the root with 2 to 4 inches of soil, then water the plant well.
Spring-planted horseradish roots will be ready to harvest in October or November. Harvest the roots in the fall, ideally after the first frost. Dig around the base of the plant and lift the large, central root and as many of the smaller roots as possible. In frost-free climates, winter harvest is recommended. If you want to eat some young horseradish greens, harvest them before the bugs eat too many holes in them. They grow back in a week or so.
In general, horseradish is a forgiving plant that can handle a wide range of settings. Ideally, however, horseradish thrives in full sun or partial shade.
Horseradish is not a demanding plant, but you will get better-quality roots if you keep the soil well watered, so the roots do not get woody.
Temperature and Humidity
Horseradish likes cool weather. Its ideal daytime temperatures range from 45 to 75 degrees Fahrenheit.
Feed or side dress your plants every three to four weeks. You can fertilize with compost, compost tea, or a commercial 10-10-10 vegetable fertilizer (following the product instructions).
If you are growing your horseradish as a perennial, you can leave some in the ground and harvest as needed. Just keep in mind that the more broken pieces left in the ground, the more plants you will have the next growing season. Alternatively, you can lift all of the roots and save some for the next year. Saving it is often the preferred method because horseradish can become aggressive.
Varieties of Horseradish
Common horseradish may be the only variety you will find. There is also Armoracia rusticana 'Variegata,' which is more ornamental, with marbled leaves.
Few pests will bother the roots of horseradish, but there are several that will feed on the leaves, including aphids, beet leafhopper, diamondback moth, flea beetles, and imported crucifer weevil. The aphids can be washed off. If the other pests become a nuisance, consider growing your horseradish undercover.
Growing Horseradish in Containers
If you are worried about horseradish taking over your garden, growing it in a container may be a better option for you. You'll need a sizable container, with at least a 30-inch depth for the roots to grow in. Plant the roots the same as if you were planting them in the ground. Container horseradish will need more frequent watering and monthly fertilizing.
Growing Horseradish as an Annual
To get large horseradish roots like the ones you purchase in a store, consider experimenting with growing the plant as an annual, focusing on getting one large root rather than many smaller roots. First-year roots tend to be the most pungent.
Start with a bed prepared with lots of organic matter, and plant the roots as you would in the ground. As the plant starts to grow, it will send up multiple shoots. Each shoot is forming small roots and taking energy from the plant. To get one large root, remove all but one or two of the shoots and allow them to grow larger.