Hi Linda,
You've asked a question that I know very little about. Although I love them, I have never grown them. So I must disqualify myself right here.
I will leave this open to others who might see this question. Meanwhile I've run across a couple links that look very promising. Hope this helps! And maybe someone with experience will jump in here too.
http://garden.org/ideas/view/S...
http://garden.org/ideas/view/d...