Can Lettuce Be Grown Indoors?

Pots and Containers

• Lettuce maintains compact, predictable growth, with shallow root systems and short seasons, and so thrives in planters, pots and containers. The Ohio State University Extension suggests broad, flat containers for multiple lettuce plantings, although traditional 3-gallon pots work as well. Use containers with drainage holes to promote quick drainage and circulation.

Potting Soil

• Container soils must provide quick drainage, nutrition, moisture retention and a loose consistency for growing success. Lettuce requires a particularly moist foundation and fares best with high-quality potting soil. Use a mix of 1 part peat-based potting soil to 1 part organic compost and add vermiculite for better moisture retention. Turn 10-10-10, 13-13-13 or 14-14-14 granular fertilizer into the soil for long-lasting nutrition.

Light and Temperature

• Keep lettuce in appropriate sites for light and temperature. The Ohio State University Extension recommends temperatures of 45 to 65 degrees F for best lettuce production, while the University of Illinois Extension warns that lettuce experiences stunted growth and inferior quality at temperatures over 70 degrees F. As a cool-season plant, lettuce thrives with 4 to 5 hours of sunshine or artificial light every day.

Care and Harvest

• Water lettuce deeply every 4 to 5 days to keep the top 2 inches of soil moist. Lettuce crops fail in dry soil, but thrive with consistent moisture. Give the lettuce water-soluble 20-20-20 or 15-30-15 fertilizer in mid-season, per the manufacturer's directions, to promote best growth. Harvest lettuce heads when they reach desired size and become firm and round. Young, tender lettuce produces the best harvest while older lettuce produces tough, bitter and woody foliage.