Growing lettuce from seed is a rewarding and cost-effective way to ensure a consistent supply of crisp, flavorful greens. This cool-season vegetable is relatively simple to cultivate, making it an excellent choice for new gardeners. Understanding the specific needs of the seeds and plants allows you to easily transform a packet of tiny seeds into a thriving salad garden.
Selecting Varieties and Optimal Timing
Choosing the right type of lettuce is the first step toward a successful harvest. Varieties generally fall into loose-leaf, butterhead, or romaine categories. Loose-leaf types, such as ‘Black Seeded Simpson,’ are the easiest for beginners, offering a fast harvest and a long production window. Butterhead varieties, like ‘Buttercrunch,’ form a loose head and are known for their sweet, buttery texture.
Lettuce is a cool-weather crop that thrives in temperatures between 60°F and 70°F. It will quickly become bitter and “bolt” (send up a flower stalk) when temperatures consistently climb above 80°F. Therefore, it is best planted in early spring and again in late summer for a fall harvest.
To ensure a continuous supply of fresh greens, succession planting is highly effective. This involves sowing a small batch of seeds every two to three weeks rather than planting the entire packet at once. This practice staggers the maturity dates, preventing a temporary glut followed by a gap in your harvest.
Sowing the Seeds
Lettuce seeds require careful attention to the planting environment for successful germination. Whether starting seeds indoors or sowing directly into the garden, a light, well-draining soil medium is necessary. Lettuce seeds can germinate at soil temperatures as low as 40°F, but they perform optimally between 55°F and 65°F.
For direct sowing outdoors, the soil should be finely raked and free of large clods or stones that could impede the tiny seedlings. Lettuce seeds require light to germinate, so they should be sown very shallowly, covered with no more than one-eighth to one-quarter of an inch of soil. Sowing them too deep can significantly reduce the germination rate.
After sowing, the area must be kept consistently moist with gentle watering, such as a fine mist, to prevent the seeds from being washed away or drying out. For head-forming varieties like romaine, aim for a final spacing of 8 to 12 inches between plants. If starting indoors, use shallow containers and ensure seedlings receive adequate light as soon as they emerge to prevent them from becoming leggy.
Essential Care for Healthy Growth
Once lettuce seedlings have developed their first set of true leaves, the most important step is thinning. Thinning is necessary because overcrowded plants compete for light, water, and nutrients, leading to stunted growth and increased susceptibility to disease.
Carefully remove the weaker seedlings by plucking them out or snipping them at the soil line, leaving the strongest plants at the recommended final spacing. For loose-leaf varieties, a spacing of 4 to 6 inches is adequate, while larger heading types require more space. The removed seedlings are edible and can be used as fresh microgreens.
Lettuce is a shallow-rooted plant, requiring consistent and uniform moisture to produce tender, non-bitter leaves. Inconsistent watering stresses the plant and can lead to premature bolting. Water deeply when the top inch of soil begins to feel dry. While lettuce prefers full sun, providing partial shade during the hottest part of the day can help delay bolting and extend the harvest season.
A moderate feeding regimen is sufficient, as lettuce grows quickly and does not require heavy fertilization. A balanced, water-soluble fertilizer applied every two to three weeks provides the necessary boost for vigorous leaf production. Monitoring for common pests like aphids and slugs is also important. A strong spray of water can often dislodge aphids, while physical removal or simple traps are effective against slugs.
Harvesting for Maximum Yield
The way you harvest lettuce directly impacts the total yield and the longevity of the plant. Loose-leaf and butterhead varieties are well-suited to the “cut-and-come-again” method, which allows for multiple harvests from a single plant.
To use this method, harvest only the outer, mature leaves, leaving the central growing point (crown) intact. Use clean scissors or a sharp knife to snip the leaves one to two inches above the soil line. This technique encourages the plant to continue producing new leaves from the center, allowing you to harvest fresh greens every two to three weeks until the plant bolts.
For head-forming varieties, such as romaine, the entire head is harvested at once when the center feels firm when gently squeezed. Cut the plant at the base just above the soil line. Harvesting is best done in the morning after the dew has dried, as the leaves are at their crispest. Store the unwashed leaves in a loose plastic bag in the refrigerator to maintain freshness.