Iceberg Lettuce (Lactuca sativa) is a temperate annual or biennial plant of the aster or sunflower family Asteraceae. It is most often grown as a leaf vegetable, but also sometimes for its stem and seeds. Heading varieties of lettuces are commonly started in flats, then transplanted to individual spots, usually 8 to 14 inches (20) to 36 cm) apart, in the garden after developing several leaves. It is best transplanted. Plants thrive well with temperature ranges from 10-15°C. Plants mature at 70-90 days after sowing.