Grew them last year, and loved them. Very productive, good flavor and texture. Going to grow more this year.

Here's a good source, where I got mine from:

Here is a link that might be useful: Nichols Garden Nursery

I grow them too. They are really neat.

I also bought mine from Nichols. I wasn't terribly impressed with the taste and thought they were quite bland but they did become sweeter after being stored for a short time. I do like the texture and they are a good addition to stir fry and salads. Make sure you give them plenty of space as they get huge!