Salads are a favorite meal in our home, which made growing lettuce a priority when space was carved out for a vegetable garden. It quickly became a favorite vegetable to grow, too. Homegrown lettuce, harvested and eaten straight away, is much more flavorful than greens from the grocery store. It is also a quick crop, with some varieties ready for harvest only weeks after sowing. It’s the fast food of the edible garden.
With a bit of planning, you can grow lettuce to be harvested throughout the season, even during those hot summer months when lettuce tends to bolt. To keep the lettuce coming, you need to adjust your planting schedule, carefully select varieties and keep seedlings on hand for transplant. With these techniques, you’ll be able to harvest fresh lettuce for most of the growing season—even in cold weather with extra protection.
To grow healthy plants, give your lettuce well-drained soil that is rich in nitrogen. Lettuces like temperatures cool, too, which is why they bolt during hot, dry weather. Head lettuces also need space to mature because overcrowding increases the risk of bolting.
For a long season of lettuce, you’ll want a mix of cold-tolerant and warm-weather varieties, as well as a few all-around winners that do well across all seasons. Select some lettuce mixes that produce a quick harvest of small leaves as well as varieties that produce heads, which take much longer to reach maturity.
I grow mostly butterhead varieties with some leaf and romaine types mixed in for quick harvests. I also have a small patch of mesclun growing all season to augment the main lettuce crop.
Sow Early But Not Too Often
Gardeners are often advised to seed lettuce every 10 days to two weeks for a continual harvest. I have found that this is much too often and results in plants maturing at the same time instead of in succession. In my cold-climate garden, I seed every three to four weeks, which produces a true succession and reduces my workload. I also plant twice as much lettuce as I think I will need. This allows for the inevitable plant failure and pest damage. Since lettuce can be harvested at most stages of growth, even with planting less frequently, you’ll have plenty of small leaves and small immature heads to eat before heading varieties fully mature.
Seeding indoors and transplanting seedlings provides more consistent results and increases yield from a small garden. Lettuce directly seeded into the garden is also much more likely to be ravaged by pests or be washed away by heavy rains. Having seedlings ready to replace harvested crops will make it easier to maintain a regular crop for harvesting by reducing windows of waiting for plants to mature by two or three weeks, which is important for those of us who have short growing seasons. Indoor seeding also protects seedlings from temperature extremes in both spring and summer, which makes plants last longer in the garden. I sometimes thin the flats of seedlings to provide a salad or two to augment the garden harvest.
Once plants have reached a certain size, outer leaves may be harvested sparingly. My rule is: when plants have 10 leaves, the outer three or four leaves may be harvested without too much effect on plants. Allow a few prize heading plants to fully mature without harvesting any outer leaves.
Even with the best varieties and a careful seeding schedule, lettuce is most susceptible to bolting when the weather is hot and dry. Lettuce that has experienced the cold weather of spring is more likely to bolt when the weather turns warm than young plants that were started indoors and are accustomed to warm weather. To reduce the risk of bolting, be sure to water plants well and regularly. Protect plants from the sun on the hottest summer days (high 80s and 90s F). Something as simple as a cardboard tent over the lettuce patch during the hottest part of the day can keep plants from bolting; shade cloth over hoops also works well. Consider planting lettuce in the shade of taller plants, like peppers and tomatoes, for shelter. If you do plant lettuce close to other plants, remember the plants will need more water and fertilizer.
Lettuce that has started to bolt can be bitter—how bitter depends on the variety. Keep a close eye on plants as weather warms. When you notice the telltale signs of bolting, harvest immediately. Taste a leaf or two to see if it is bitter. If it is, pull the plants and replant with seedlings. If the leaves aren’t bitter, harvest and eat, then replant with seedlings. This is where having a flat of seedlings in waiting will maximize harvest as two- to three-week-old seedlings may be ready to harvest in two or three weeks, depending on the variety.
Extending the Season
Plants in the shoulder seasons mature at a slower rate than they do during the height of summer, so having more plants during these times is a good idea. Be sure to grow lettuce varieties that are cold-tolerant and mature when they hit fall as they won’t grow much after the end of September.
Some lettuce varieties can take light frosts, but even those appreciate some cover when the temperature dips. Lettuce can be protected with cloches, floating row covers (like agribon/remay), cold frames and greenhouse plastic, if you want to keep them in the ground in the fall.
To keep your plate overflowing with leafy greens throughout the growing season, choose a mix of varieties, keep the plants coming and be ready to harvest by the head or the leaf. Under the right conditions, you can grow lettuce for most of the season, keeping you in nutritious salads for months.
Susy Morris is a garden photographer and writer based in Maine. Her blog is chiotsrun.com.