You may be eating less salad these days. Everyone’s making fewer trips to the supermarket, and lettuce and other tender greens are easily perishable. But growing your own lettuce is a great solution—now and going forward. Lettuce is fast growing and ideal for backyard gardens. You can pick individual leaves each day or harvest whole heads at once. By starting a new set of seeds or transplants every few weeks, you can create succession plantings to ensure a continuous salad bar!
Temperature and Varieties
Lettuce does best in cool climates or during cool seasons. At higher temperatures, lettuce can bolt (flower), become bitter, and form loose heads.
No problem! Just make sure you select the right lettuce. Varieties with tolerance to high temperatures can be grown in warmer areas year-round.
The variety commonly called ‘Mānoa’ lettuce, identified by CTAHR researchers as ideal for Hawai‘i conditions, has always been a local favorite. It has a buttery flavor and crisp texture—my family loves to eat it with a little mayonnaise and shoyu as dressing.
However, in recent years, ‘Mānoa’ lettuce has become extremely sensitive to heat. It may prematurely bolt and develop “tip burn” on the leaf edges. So CTAHR has identified ‘Ānuenue’ as a more heat-tolerant variety. Similar to ‘Mānoa’, it’s another local favorite that can be grown at low elevations. Both can be grown year round in Hawai‘i, and the seeds are available from the UH Seed Laboratory (which offers mail ordering).
There are plenty of other lettuce varieties you can try—just look for types that say they’re heat tolerant. Plant several for a rainbow of colors and tastes!
Nip Problems in the Bud
Besides heat, tip burn can be caused by not enough water, too much fertilizer, or not enough calcium in the soil—but these conditions are easy to fix. First, try watering your lettuce more, then ease up on the fertilizer. As a last resort, add a soil supplement containing calcium.
Thrips, birds, and spotted-wilt virus can also affect your backyard lettuce crop. Consult the UH Cooperative Extension service for the latest pest-control techniques.
Be sure to wash lettuce and other produce thoroughly before serving, to remove any tiny snails or slugs that might be on it.
Feed Your Heads
Lettuce grows best in soils rich in organic matter with a neutral pH. Add organic compost, properly composted chicken manure, and a sprinkle of triple superphosphate fertilizer (0-45-0) to the planting hole for a healthy start. If you can’t find superphosphate, a general-use fertilizer such as 16-16-16 is fine.
After planting, apply a dry general-use fertilizer every three to four weeks or fertilize every two weeks with a water-soluble fertilizer. Because lettuce is eaten raw, use clean, potable water for overhead irrigation and when fertilizing.
Jari Sugano, O‘ahu County Administrator, College of Tropical Agriculture and Human Resources