So many herbs are useless when dried, and this is one of the worst!
I have tried many varieties, saying they were "slo-bolt", but to no avail. And many people have told me that it likes cool weather, but this makes no sense, when you consider the regions where this is used the most in their cuisines - Mexico, and other Latin American areas in the tropics, southern India, and SE Asia. These areas don't import all of their cilantro from far away, like we do!
I got some of that Indian coriander seed to plant this season - first season I've seen it in a catalog! Though it's for producing seed, maybe it is also used for leaves over there - I'll find out. Even to produce a large number of seeds, the plant should get large, before bolting. All of mine would be skimpy little things, with a small seed stalk.
I've tried sprouting the Thai coriander seeds (small, reddish, strongly flavored), but none sprouted, so they might be irradiated.
I keep trying, due to my love for cilantro!