Lettuce is a popular cool-season vegetable that offers a fresh, crisp addition to any meal. Its success relies almost entirely on precise planting times, as it thrives only in moderate temperatures. Growers must monitor the calendar and climate closely to avoid periods of intense heat. Since lettuce quickly becomes bitter and inedible when temperatures rise, timing is the most significant factor in achieving a sustained and productive harvest.
Timing Spring Planting
The earliest possible planting in spring is determined by the average date of the last expected frost in your area. Lettuce seedlings are hardy and can tolerate light frosts, which are temperatures just below 32°F (0°C). For an early start, begin seeds indoors approximately four to six weeks before that last frost date. The optimal time to transplant these young plants into the garden is three to four weeks before the final frost, allowing them to handle the residual chill.
Direct sowing seeds into the garden soil can begin as soon as the ground is workable, typically around the same time as the transplanting window. While lettuce withstands a light freeze, it needs protection from a hard freeze that can damage young foliage. Using a row cover or a simple cloche system protects early plantings if a sudden, deep cold snap is forecasted. This early timing ensures the plants mature during the mild spring weather before the intense heat of summer arrives.
Planning for Continuous Harvest
A technique known as “succession planting” ensures a steady supply of fresh leaves by preventing a massive harvest all at once. Instead of planting the entire batch of seeds on a single day, stagger the sowings over time. Planting a small number of seeds or transplants every two to three weeks creates a continuous queue of maturing lettuce plants. This method provides a manageable flow of produce, which is ideal for quick-maturing crops like lettuce.
As the weather warms in late spring, shorten the time between plantings because the plants mature faster in higher temperatures. Pay attention to the variety’s “days to maturity” listed on the seed packet to plan intervals effectively. Starting a new, small batch whenever the previous one is well-established serves as a practical way to schedule sowings.
Timing Fall Planting
The second major window for planting lettuce occurs in late summer for a fall and early winter harvest. This timing requires focusing on the first hard frost date in your region. To determine the final day to plant, count backward from that average first hard frost date. Start with the variety’s listed days to maturity, and then add two additional weeks to that number.
This extra period is factored in because the cooling temperatures and shorter daylight hours of autumn naturally slow the plant’s growth rate. Planting too late means the lettuce will not reach full size before a killing freeze arrives. Fall-harvested lettuce often has a sweeter flavor compared to spring crops because the cold weather causes the plants to store more sugars.
What Causes Lettuce to Bolt
The primary environmental factor that signals the end of the lettuce growing season is a process called bolting. Bolting occurs when the lettuce plant prematurely shifts focus from producing edible leaves to developing a tall central stalk for flowering and seed production. This transition is triggered by two conditions: high temperatures and long daylight hours.
Most lettuce varieties begin to bolt when daytime temperatures consistently exceed 75°F (24°C). Once the plant bolts, the leaves rapidly become bitter and tough due to a surge in a milky, latex-like substance. For the best quality, gardeners must cease planting new batches when the summer heat arrives and focus on the cooler seasons of spring and fall.