- Horseradish isn't grown from seed, but from root cuttings.
- Choose a sunny location and allow for at least 18 to 20 inches between plants.
- Best to start in mid-February
- Though horseradish will thrive even when neglected, you can help your plants out with a mid-summer application of a low-nitrogen fertilizer.
- While the plants are growing, you can actually pick a few of the young leaves and add them to salads. They can be kind of spicy, so only try a few. The older leaves will be too tough to eat.
- Later in the season, your plants may go to flower. Horseradish blooms are small, white and not particularly showy. They won’t harm your future root harvest so don’t feel you have to cut them off like with many other herbs.
- Flea Beetles
- Aphids: Curling leaves may mean that the plant's sap is being sucked by insects. Apply soapy water to all sides of leaves whenever you see aphids.
- Downy mildew: Yellow patches on leaves are usually caused by moist weather. Keep leaves as dry as possible with good air circulation. Buy resistant varieties.
- Cabbage loopers: Small holes on the leaves between the veins mean small green caterpillars are present. Look at the undersides of the leaves. Hand pick if the problem is small or control with Bacillus thuringiensis. Use a floating row cover just after planting through harvest to prevent caterpillars.
- Cabbageworms and other worm pests: Treat same as loopers.
- Nitrogen deficiency: If the bottom leaves turn yellow and the problem continues toward the top of the plant, the plants need a high nitrogen (but low phosphorus) fertilizer or bloodmeal. Blood meal is a quick Nitrogen fix for yellowing leaves.
- Clubroot: Quickly wilting plants may be due to this fungus in the soil. The entire plant, including all roots and root tendrils, must be gently dug up and removed. If the roots are gnarled and misshapen, then clubroot is the problem. Act quickly to remove the plants so that the fungus doesn't continue to live in the soil. Do not compost the plants. Raise the pH of your soil to above 7.2. You may need to sterilize your soil, too.
Harvest and Storage
- You can either harvest your horseradish in the fall after the first hard frost has killed back the top portions of the plant, or in the early spring just before new sprouts form.
- Root flavor intensifies quite a bit after a frost but if you prefer milder horseradish, than harvest a bit earlier.
- Dig up your plants and cut away all the thick roots.
- To start new plants for the next year, leave one or two pieces in the soil.