Dill and Cilantro

So, even though Cilantro was a pain in the ass to grow in Texas because it was too hot, I've had some success getting them started here in PA.  What I don't know, is how long the weather can keep them from bolting.  Given that the strain is an heirloom, I can select for late bolting (bolting is where the plant rapidly moves from the vegetative to the flowering state) but we do love some cilantro and dill.  The dill will be awesomes for canning later on.