Container Lettuce

A window box of leaf lettuce will grow to maturity in 6-8 weeks and then will produce enough lettuce for a good-sized salad once a week for 6 weeks. I plant a group of boxes (usually 3), wait 6 weeks, and then cut 1 box for 1 salad. (With 3 boxes, I cut 3 times a week–one box on Monday, another box on Wednesday, etc.).

When I start cutting the first set of boxes, I plant the next set of boxes. The second set will be ready for cutting just as the first set is done producing. If you want more lettuce, plant more boxes—just be aware of the six-week rotation. I plan for indoor lettuce for 8 months of the year, or about 32 weeks. That means planting about 5-6 times.

Teri’s steps for container lettuce

  1. Choose a container. I like 28” to 36” window boxes that have drip trays. You can also use wallpaper troughs that don’t allow drainage. Lettuce puts down shallow roots and doesn’t need much drainage. However, don’t ever put a wallpaper trough out in the rain, or it will fill up with water and drown the lettuce.
  2. Fill the containers with potting soil. I use approximately 1 bag (1 cubic foot) of potting soil to plant 2 window boxes. (I buy 9 bags at the end of the summer season for 18 boxes during the winter.)
  3. Plant 2 rows of seed the length of the box. I use approximately 1 package of lettuce seed to plant 2 boxes. (I store 9 packages of seed for 18 plantings.) My very favorite variety of leaf lettuce is Burpee’s Gourmet Blend. Be aware that lettuce seed will store and germinate well for only 3-5 years.
  4. Water gently. (I use a ketchup squirt bottle.)
  5. Cover the box with plastic wrap to keep the soil moist. When seedlings start to appear, remove the plastic wrap. If you have cats, put wood skewers into the soil to keep the cats from using it as a litter box.
  6. Water approximately every other day.
  7. Most potting soils contain sufficient fertilizer for the lettuce life cycle. If not, add fertilizer to your watering.
  8. Leaf lettuce produces well in a south-facing window if it doesn’t get too hot. Alternatively, use long, fluorescent grow lights. Keep the bulbs just barely above the leaves. I use 4-ft. shop light fixtures that hang from chains from the ceiling. The bulbs are sold in hardware stores and Walmart as either plant/aquarium bulbs for old-style fixtures or as blue (~6500K) and red (~3000K) spectrum for new-style fixtures. Lettuce likes cooler temperatures, so it does well in a basement under lights.
  9. Cut leaf lettuce with scissors, carefully choosing the largest leaves and leaving the smaller leaves to continue growing. Be sure to cut above the “v” where the new growth is forming. Baby leaves will emerge from the “v” and continue growing to full size. If you cut next to the soil, the lettuce will not produce any new leaves.
  10. If you want to grow lettuce outside in containers, the same instructions apply. Choose a location that gets 6-8 hours of sunlight. You can grow larger varieties of head lettuce and other varieties of greens outside if you provide good exposure to sunlight and fertilize regularly.