I grow mine in a large pot. A few years ago I saw a horseradish pot advertised which was two pieces, one with openings top and bottom that fit on top of another normal-shaped pot. They were made of clay and looked very nice, but were much too expensive for my budget. So I took a large 10 gallon plastic pot, filled it with potting soil, planted my horseradish root, then inverted another pot that was slightly smaller in diameter (with the bottom cut out) over the first pot. I then filled the top pot to the top with soil and watered. When I harvest, I simply pull the top pot off and the roots are easily accessible. It works for me. Just be sure to put something under the bottom so the roots can't escape. I use weed barrier.

My understanding is that it is only "invasive" if you disturb the roots greatly. The little broken off root bits grow into new plants.

FataMorgana

If you have the room you will not need to worry about it being invasive. Only if it is planted too close to other plants. It has to be dug up every other year anyway or the roots will get too woody, for best results the newer roots seem to be the best, plenty hot, not like what you buy in the stores.

if you have to worry about something taking over a square yard of space all for itself?

pot it in the biggest fiberglass pot you can, and surround it with nasturtiums if you like - the effect is quite tropical, actually : )

harvest by kicking over the planter.