Growth Cycle of Red Lettuce

Germination

A cold season crop, lettuce germinates best at a temperature below 70 F; higher temperatures could cause seeds to go dormant. Germination occurs in about two days at that temperature and in about a week at 50 F. Plant in early spring or late summer, avoiding the hottest summer temperatures, which will reduce leaf size and turn the flavor bitter. Leaves are harvestable in as little as 30 days, but reach full maturity in 45 to 60 days or more, depending on variety.

For the first couple of weeks after emergence, young lettuce seedlings begin their vegetative stage of growth. During this period, the lettuce plant will begin to form a head and an arrangement of surrounding leaves. Many red lettuce varieties are of the loose-leaf type and will produce a loose arrangement of leaves that can be harvested continuously. These lettuce types mature sooner than other types of lettuce, in 45 to 60 days. Romaine varieties of red lettuce are more upright in their growth habit, with close-knit leaves usually harvested in about 60 days. When it comes to lettuce, harvest time is up to the grower and is dependent on the size of leaf desired.

After about two months of growing or in response to heat or stress, red lettuce will begin bolting. The stem of the plant shoots up quickly and leaves diminish in size. Lettuce should be harvested before bolting occurs since the leaves will turn bitter during this time. The bolting stage continues for 30 days as plant prepares to go to seed. To prevent bolting, provide shade or cover for lettuce, move to a cooler location or simply plant bolt-resistant varieties.

Depending on the variety, lettuce begins to flower after two to three months, continuing for three to four weeks. The stem and branches extend and produce flower heads at their ends. The lettuce reaches a significantly greater height than is seen during edible stages. Once flower heads open, the seeds within start ripening and are ready in 11 to 13 days.

Red Sails is the slowest bolting variety of red leaf lettuce and is ideal for late sowing or late harvest. Red Fire is a ruffled variety that is also slow to bolt. While most red lettuces are loose-leaf type, Cimmaron is a Romaine lettuce with dark red leaves and is likely to take about 70 days to reach maturity. Red Rosie is another Romaine variety with bright red color that is tasty whether eaten young or full-grown.