Choose among leaf, butterhead, romaine (cos) and crisphead (also known as “iceberg”) lettuces. Start seeds in flats indoors about 4 weeks before planting time; or buy transplants. Set out transplants (or sow seed directly in the garden) in early spring; make successive plantings or sowings until daytime temperatures reach 75 degrees to 80 degrees F/24 degrees to 27 degrees C. Plant again in late summer and early autumn for fall crops.