Lettuce is a garden favorite and one of the first vegetables that can be planted in the spring. As a cool-season crop, its growth is highly dependent on timing, which dictates whether you will harvest sweet, crisp leaves or bitter, bolted plants. Successfully growing lettuce outside requires carefully planning the planting dates around local weather patterns. The goal is to ensure the plant matures before summer heat triggers bolting, where a flower stalk emerges and the leaves become unpalatable.
Determining the Ideal Spring Planting Window
The best time to start planting lettuce is not when the air feels warm, but when the soil is ready. Lettuce seeds are cold-tolerant, capable of germinating in soil temperatures as low as 40°F, although they sprout fastest when the soil is ideally between 55°F and 65°F. This cold tolerance means you can begin sowing seeds earlier than most other vegetables. A reliable guideline is to aim for planting approximately two to four weeks before the average last spring frost date in your region. This early start capitalizes on the cool, moist conditions that lettuce thrives in. While young seedlings are more sensitive, mature lettuce plants can often tolerate a light frost, surviving brief dips down to 25°F to 32°F if they have been gradually acclimated to the cold. The biggest threat to a spring crop is not the cold, but the premature arrival of high temperatures. Lettuce grows best when air temperatures are between 60°F and 65°F, and prolonged exposure to temperatures above 75°F can quickly cause the plant to bolt.
Timing Differences: Direct Sowing vs. Transplants
The method you choose for planting—direct sowing or transplanting—affects your precise timing. Direct sowing involves planting seeds directly into the garden bed, which can be done as soon as the soil is workable in early spring. This method is straightforward and allows the plant to develop an undisturbed root system. Starting with transplants means growing seedlings indoors for four to six weeks before moving them outside. These young plants are more sensitive to temperature swings than seeds, so they should be planted out slightly later, typically three to four weeks before the last expected frost. Transplants must undergo hardening off, where they are gradually exposed to outdoor conditions over a week or two, helping them survive the shock of being moved to the garden. Using transplants offers the advantage of a head start, yielding a harvest up to two weeks earlier than direct-sown seeds. However, the initial shock of transplanting can slow the plant’s growth if the soil is still too cold.
Extending the Harvest Through Succession and Fall Planting
Succession Planting
To avoid having a single, overwhelming harvest, employ succession planting. This technique involves staggering small plantings of lettuce every ten to fourteen days during the spring season. By sowing new seeds or planting new transplants regularly, you ensure a continuous supply of fresh, tender leaves. This staggered planting should continue only as long as the weather remains cool, typically stopping when daytime temperatures begin to consistently exceed 70°F. Once the heat of summer arrives, the risk of bolting becomes too high, and the quality of the harvest diminishes. Starting small batches is the key to managing the supply and preventing waste.
Fall Planting
The second major planting window for lettuce occurs in late summer for a fall harvest, which often produces the sweetest leaves. The cooling temperatures and shorter days of autumn are ideal for lettuce growth, as they slow the plant’s metabolism and prevent bolting. To time this harvest correctly, sow seeds directly into the garden approximately six to eight weeks before the average first fall frost date. This timing allows the plants enough time to reach a mature size before freezing temperatures arrive. If planting a variety with a long maturity period, you may need to start the seeds indoors during the heat of late summer, as high soil temperatures can inhibit germination. Fall-grown lettuce benefits from the lack of summer heat stress, resulting in a milder and sweeter flavor.