my little horseradish plant

I've got a little horseradish plant in the back corner of my garden. It's the first time I've tried growing this. I looked up information on horseradish culture and it sounds like I should let it grow another year before I harvest some of the offshoots.

When grown as an annual, it requires a long growing season. It needs warm temperatures during the summer growing season and cooler temperatures in the late summer and fall to enhance root development. In the annual system, the crop is usually planted in the early spring, and the entire root mass is harvested after the first killing frost in the fall. In the perennial system, upright, thickened, underground shoots arising from a deeply planted “mother” root are harvested every other year, with the original plant left in the field for regeneration. Perennial fields may stay in production for 10 to 20 years. Perennial culture generally requires more labor and growing skill. It is still practiced in some areas, particularly where there is a short growing season. Once introduced to a farm, horseradish can be difficult to eradicate completely as any size root or piece can readily begin a new plant. from Virginia Coop Ext