(Horseradish) Horseradish Crowns are adapted to the north and are not suited for southern planting except in high altitudes. One plant is quite large and will need a big area in the garden. Not much is needed for the average family, and a few plants will provide roots for an ample supply of grated or ground horseradish. To prepare horseradish, clean and grate the roots into white wine vinegar or distilled vinegar of 4 1/2 to 5 per cent acid content, bottle and seal at once. Horseradish makes its best growth in the cool autumn, steadily improving after September and not injured by early frost. Harvest late fall with a spade.