We planted three different beets this year, Golden, Detroit Red and Lutz.
I've been looking for a long season beet for a couple of years now and finally found the Lutz variety for sale on Ebay. You can let them grow really big and they won't get woody. As you can see from the photo, the Lutz grew the biggest. I'm going to pot up a couple of beets for replanting in the spring. Hopefully then I'll get a nice harvest of seeds from them. Lutz are the only beets I'll be growing from now on.