Crisp, sweet head lettuce is a mainstay for those first barbequed burgers and spring salads. Head lettuces like iceberg and romaine require cool temperatures and grow well in spring or fall in most zones. Gardeners in warmer climates with shorter cold periods may find they get no head on lettuce crops. If you ask why my lettuce is not forming heads, you’ll need to know the reasons for no lettuce heads. Head lettuce problems can be prevented by using transplants or planting in fall in most regions.
Help, My Lettuce is Not Forming Heads
Lettuce is a cool season crop that will bolt or fail to fix heads when daytime temperatures are higher than 70 degrees F. (21 C.) Although relatively easy to grow, head lettuce problems may range from slug and snail damage to loose heads. Pest problems are easy to deal with, but only climactic conditions can ensure head formation. Fixing no head formation on your lettuce crop means providing temperatures and site conditions that encourage formation.
Reasons for No Lettuce Heads
Lettuce grows well in organically rich soil with superior drainage. Sow the seeds in early spring after working in a layer of organic matter and tilling to a depth of at least 6 inches (15 cm.). Direct sow seeds in prepared soil where the plants will receive indirect light and are protected from the hottest rays of the sun. Spread a thin, 1/8 inch (3 mm.) layer of fine soil over the seeds and keep lightly moist.
Thin plants that are sown outdoors to at least 10 inches (25 cm.) apart. Failure to thin the plants will prevent them from having the room to form adequate heads.
Plants that are grown late into the season will face warmer temperatures, which prevent the formation of tight heads. If you find no head on lettuce a consistent problem, try sowing in late summer. The cooler temperatures of fall provide the ideal conditions for maturing seedlings to produce crisp heads.
Fixing No Head Formation
Lettuce is very sensitive to heat and exposure to summer temperatures or a warm spell can keep them from forming correctly. Head lettuce is more suited for northern climates, but gardeners in warmer zones can successfully produce the green.
Start seeds indoors in flats and transplant at least a month before high temperatures are expected. Head lettuce problems that prevent tight forming leaves also include spacing. Transplant the seedlings 10 to 12 inches (25-31 cm.) apart in rows 12 to 18 inches (31-46 cm.) apart.
Other Head Lettuce Problems
Head lettuce needs cool temperatures and shorter day lengths for best head formation. When planted too late in the season, the plant will bolt (form seed heads). The greens also get bitter when temperatures are higher than 70 degrees F. (21 C.).