Plant Societies Botanical Gardens Hort. I'll try to help you. For additional info, there's my Cyber Sites for Herbs - if you find one that doesn't connect, please email me.
Propagation is by root division.
It needs cold weather to develop its characteristic flavor. The root may be dug and one-inch of the top replanted to ensure a future plant. May be dried, but loses some potency in the process. When preparing horseradish, be sure to have windows open to allow ventilation. When the vinegar is added, the horseradish is activated.