I tried Romanesco last year from seed and even though the plant grew to 4 ft high by 4 ft wide, it never grew a head!?? Tried again this year. Planted first week in May and it's now August and larger than 3'x3' with no sign of a head. Both plants in full sun in a raised bed in Zone 6a. Does anyone have an idea of what is wrong? Did I start it too late?
Is it too late for another try at a midsummer planting?

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.

Don they do seem to do better as a fall crop but I've gotten heads in early summer by spring planting. That said I'm in SC so our daylight hrs are shorter then CT in summer and more hrs of light than dark keeps some plants in vegetative growth. I'm not sure if this applies to Romanesco but it seems plausible if you both are in the northern part of the US and having the same problems.