Don, that's exactly what happened to me when I tried starting this plant in the spring; when I grew it in the past for a fall crop, however, it headed up very nicely. I started seeds about 5 weeks ago and have just put them out in the garden, so with the zone difference (I'm really more like zone 4b than 5a) I think you might be okay yet. They're pretty cold hardy but you could always give it a little protection with floating row cover or something toward the end if you needed to.
