The plant is propagated from root cuttings made from the laterals removed when the roots are trimmed or prepared for market. The longest pieces produce the largest roots. They generally range from 4 to 6 inches in length and average about ¬ inch in diameter. As these roots are nearly uniform in girth, they are cut square at the top to denote which end is to be planted up; the lower end is always cut obliquely. They should be tied into bundles of convenient size, packed in sand and stored in a cool, moist place until wanted for planting. Some growers prefer to bury in a well-drained soil. Crowns may be planted, but they produce a large number of small, branched roots which are unsatisfactory for grating or grinding.
Rotten stable manure is often employed in the culture of horse-radish. It should be plowed under rather than used as a top-dressing, because surface applications are thought to encourage branching on the upper portion of the roots. High-grade commercial fertilizers can also be profitably used. The soil preparation should be early, deep and thorough. The roots are generally planted obliquely or perpendicularly, with the tops 3 to 5 inches below the surface, although some growers prefer to place them horizontally. Furrows of the proper depth should first be made if the crop is to be planted alone, and the roots then placed 15 to 18 inches apart, with space enough between rows to operate a horse cultivator. Horse-radish is often used as a companion crop, when the roots may be planted with a spade, dibber or crowbar. (See Chapter XXIII (Succession And Companion Cropping).) Thorough tillage should be given throughout the season. The conditions are most favorable for rapid root growth during the cool weather of early fall.
As the roots are perfectly hardy, they may be left in the ground all winter if desired. Extensive growers dig a portion of the crop late in the fall, burying it in the ground or storing in root cellars or pits until sold. It is customary to harvest the remainder of the crop as early in the spring as the roots can be dug. When stored, precautions should be taken to prevent the roots from shriveling and drying out.
The reports on yields and returns vary considerably. Peter Henderson regarded five tons an acre a good average yield, although many growers do not succeed so well. Professor L. H. Bailey states that yields vary from 2 to 4 tons to the acre.