Growing cilantro / coriander in zone 7a

Last frost in zone 7a typically falls between late March and mid-April; first fall frost arrives in late October to early November. Cilantro seedlings tolerate light frost, so direct sowing can begin 3 to 4 weeks before last frost, roughly late February to mid-March. A sowing made in early March can yield harvestable leaves by mid-April. As daytime temperatures climb past 80°F in late May, plants will bolt and flower; the bolt-to-seed cycle runs roughly 6 to 8 weeks from emergence. A fall succession sown in late August to September matures before the first hard frost and typically produces through early November. Plants that bolt in summer often self-sow, and that seed germinates reliably into the fall crop without replanting.

The main adaptation in zone 7a is succession planting to outrun the heat. A single spring sowing bolts by late May; staggered sowings every 2 to 3 weeks from late February through April extend the leaf harvest into early summer. Slow Bolt and Calypso varieties add a week or two before bolting under heat stress, which helps in zone 7a's rapid spring warm-up. Summer cilantro production for leaf harvest is not practical here; a more useful approach is letting a few spring plants bolt and set seed, which replenishes the soil seed bank and often produces a fall stand with no direct effort. Zone 7a's 0 to 5°F winter minimum will kill any remaining aboveground growth, but seed in the soil overwinters without issue. The high humidity common in zone 7a can encourage damping off in seedlings; spacing plants 6 inches apart and avoiding overhead watering in the evening reduces that risk.