People have been grinding the peppery roots of horseradish into a condiment for more than 3,000 years. This tradition should be kept by more gardeners, because few plants are as easy to grow as horseradish (Amoracia rusticiana). A distant cabbage cousin, horseradish is a hardy perennial capable of surviving winter temperatures to -20°F (-28°C).
But no plant is perfect, and horseradish is a hopelessly aggressive spreader. However, as long as you never forget its invasive nature, horseradish can be a happy garden resident. Placed at the end of a row, a clump of horseradish makes a useful barrier to weeds and foot traffic.
You can make a new planting from horseradish roots purchased from a nursery, or simply use healthy roots from the produce market. Planted in fall or late winter, horseradish roots sprout leaves in spring. Plants need at least one season, and preferably two, before they are ready to dig. Established plants often develop sprays of white summer flowers, which should be removed to keep plants from wasting energy, and to prevent unwanted reseeding. Horseradish always returns the next year no matter how carefully you harvest, so you will have plenty of plants to dig and move to a new spot in spring. Weedy seedlings would only be a nuisance.
How to Harvest Horseradish
Cool soil promotes the formation of compounds that give horseradish roots their pungency, so it's best to harvest horseradish in fall, winter, and early spring. I'm ready to dig a plant or two by early October, mostly to have the warming effects of horseradish on the autumn table. I dig more horseradish in late November, just before the ground starts to freeze. I harvest horseradish roots again in spring, when I finish digging up older plants and dig out or move new plants that appear in bad places.
I suggest using a digging fork to harvest horseradish, and to begin by loosening the soil in a wide circle around the plant. Next, poke around with your fingers to locate the direction in which the taproot has grown. Rather than going straight down, the main horseradish root will be found running nearly horizontal in an unpredictable direction. Follow this root with your digging fork, gently excavating surrounding soil. This is the best way to make sure you get the largest roots, which easily break off if you pull plants rather than digging them out.
The easiest horseradish roots to work with are the same diameter as your fingers -- some thumb and some pinkie size, but you get the idea. I wash off the roots, pat them dry, and place them in a plastic bag or other airtight container in the refrigerator. Unpeeled horseradish gives off hardly any aroma, and will store in the refrigerator for several weeks.
How to Make Prepared Horseradish
The compounds in horseradish are activated by a few minutes of exposure to air, but destroyed by high heat. There are many ways to preserve horseradish, but the most versatile is to make "prepared horseradish," which can then be added to other ingredients to form various horseradish sauces. Add a teaspoon of prepared horseradish to a half cup of ketchup and you have shrimp cocktail sauce. Add prepared horseradish to sour cream and you have a creamy horseradish sauce for meats, potatoes, or roasted vegetables. Enrich a sweet mayonnaise with prepared horseradish and you have Arby's Horsey Sauce, familiar to most Americans. The list could go on, but I must note that coarse mustard kicked with prepared horseradish is a favourite at my house.
Many sources suggest using a food processor to pulverise peeled horseradish root, but in my experience this produces a lumpy puree, thick with little shreds of woody root. The shreds are acceptable in Russian khren, a beetroot/horseradish condiment served with meat or potatoes, but to get a smooth consistency for creamy horseradish sauces you will need a Microplane zester/grater, which shaves horseradish root into tiny threads. Grating horseradish root with a Microplane grater is slow work, but sometimes the slow way is the best way.
Before I start grating , I clean a small jar and stir together 1 tablespoon white vinegar, 1 tablespoon water, and a quarter teaspoon each of sugar and salt. This is the brine for the prepared horseradish.
Working outdoors where the fumes won't burn your eyes, grate peeled roots as finely as possible. As the flesh is exposed to air, enzymes cause substances in the roots to change to spicy mustard oil. This process stops when the grated root is submerged in vinegar. For this reason, it's best to pause every three to four minutes to move the little mountains of shaved horseradish root into the brine mixture. Mix up more brine if needed to cover the grated horseradish with liquid.
Prepared horseradish will keep in the refrigerator for a month, but it seldom lasts that long in my house. Especially in autumn, the warming effects of horseradish linger long after you enjoy a roasted winter squash slathered in creamy horseradish sauce, or a lively dollop of horseradish mayo on your favourite hot sandwich.
By Barbara Pleasant