Last April I cut the top from a horseradish, put it into water until it rooted and then planted it in my garden. It has lovely long leaves (12" high.). May I leave it in the ground to be dug up next spring? Can I repeat the process and can the side roots be planted separately at that time? Thank you!
Yes, you can leave it. Hopefully, you will also be taking care to keep the plant under control as well. Once the plant starts growing well, it can quickly become invasive. This article will help with its care: https://www.gardeningknowhow.com/edible/herbs/horseradish/growing-horseradish-how-to-grow-horseradish.htm