Horseradish is a perennial plant in hardiness zones 2–9. It can be grown as an annual in other zones. After the first frost in the autumn kills the leaves, the root is dug out and divided. The main root is harvested for use in the kitchen. One or more large offshoots of the main root are replanted to produce next year's crop. Horseradish left undisturbed in the garden spreads via underground shoots. The plant can become invasive. Older roots left in the ground become woody. They are then no longer useful for cooking. Older plants can be dug out and divided to start new plants.