I buy my cilantro at the Farmers Markets, the Asians seem to be able to grow it for a long spring
and early summer crop. Mine seems to bolt as soon as the sun shines. The rest of the year I have to buy it at the grocery store. It is one of those crops that are still pretty good even from the store. The Asian growers here bring it to the market, with roots attached. It lasts for a very long time in my fridge stored in water with a baggie loosely over the top. Maybe a greenhouse would work in the summer, if it had a/c