Horseradish

About Horseradish

Horseradish is a hardy perennial grown for its thick, fiery root, grated into sauces and condiments. It is almost too easy to grow: small bits of root left in the soil sprout again, so give it a spot where it can't take over.

A hardy perennial (NC State lists zones 4-9) that prefers cool summers; roots are dug after frost.

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

Plant root cuttings at a slant in early spring as soon as the soil can be worked. To keep it from spreading, dig the roots every year or grow it in a large buried pot or pipe.

Soil

Deep, rich, moist but well-drained loam; hard, shallow or stony soil gives poor roots.

Loosen soil 8 to 10 inches deep, mix in plenty of well-decayed compost, keep pH about 6.0 to 7.0, and follow a soil test; without one, about 1 lb of balanced fertilizer such as 10-10-10 per 100 sq ft.

Feeding

• 4 weeks after planting root cuttings: nitrogen fertilizer such as 21-0-0. Use about 1 tsp per plant beside it and water it in.
• 8 weeks after planting: nitrogen fertilizer such as 21-0-0. Repeat about 1 tsp per plant and water it in.

Fresh manure, too much nitrogen or late-season nitrogen gives lots of leaves and forked, branched roots.

Harvest

Dig roots from late fall, after a hard frost, until new growth starts in spring. Trim off the tops and side roots and scrub the main root clean.

Dig roots once a year in late October or November, before the ground freezes, and save pieces 8 inches or longer to replant in spring. Roots left in the ground two seasons turn stringy and woody.

Varieties (10)

Wisconsin Extension notes that named varieties are rarely available to home gardeners other than the ornamental Variegata. Commercial types fall into two groups: Common (broad, crinkled leaves; top root quality) and Bohemian (narrow, smooth leaves; somewhat lower quality but better disease resistance). Numbered Illinois breeding clones are grown commercially and are left out.

Pests to watch for

Flea beetles

Diseases and problems

Root and crown rot, Turnip mosaic

In the kitchen

Freshly grated root is mixed with vinegar for prepared horseradish, or into cocktail sauce, dressings and sauces for meat.

Keeping it: Store whole roots in a plastic bag with moist sand in the fridge, or in moist sand in a dark root cellar, for up to about 3 months. Keep them dark so they don't turn green.

Safety: The heat comes from mustard oils released when the root is cut or grated; grinding releases them into the air, so fresh-grated horseradish gives off very pungent fumes (Arkansas and NC State Extension).

Pets: Not listed as toxic by the ASPCA, but USU Extension warns not to feed horseradish to animals, because its volatile oils cause acute inflammation of the stomach that can be fatal.