Fresh, crisp salad greens start as small lettuce seeds. Lettuce comes in multiple varieties that range from tight, crisp heads to loose, tender leaves. However, whether you're growing iceberg or butter lettuce, all types follow the same growth stages -- from seedling to harvest.
Once a lettuce seed has been planted in the appropriate conditions, it takes approximately five days to appear through the surface of the soil. Germination refers to the process of the first shoot of the lettuce plant appearing from the seed.
Young lettuce plants, characterised by their small stature and immaturity, are in the seedling stage for approximately one to two weeks. While in the seedling stage, lettuce plants should be protected from birds and other threats by covering seedlings with a layer of netting. This stage is considered a part of the vegetative stage.
Also considered part of the vegetative stage, head formation refers to the time frame during which the head of the lettuce is formed. The head, in turn, is the portion of the plant typically consumed. Maturity is reached when the head is fully formed and ripe for harvest. The exact amount of time required, however, for the head formation stage to take place varies from 45 to 90 days from germination, based on the variety of lettuce.
The final aspect of the vegetative stage of lettuce is called "bolting." Bolting occurs about 30 days after the head of the lettuce has matured, and is characterised by a sudden growth of the plant's stem. Typically, lettuce is harvested before it bolts, as heads left on during the bolting stage will be inedible.
After the vegetative stage has subsided, the lettuce plant begins the process of producing seeds for reproduction. Approximately 60 to 90 days after lettuce plants burst through the soil, they will begin to display small dandelion-like flowers. One to two weeks after the flowers of the lettuce have opened, the lettuce seeds will begin to mature.