Can You Grow Hydroponic Lettuce Outside a Greenhouse?

Type of System

• Lettuce grows well using any type of hydroponic system. Commercially, hydroponic lettuce is most often grown using either the nutrient film technique or the floating raft system. For home gardeners, floating raft systems are a good option since they are inexpensive to purchase or build, come in a range of sizes to fit almost any space, and are easy to operate and maintain. This type of system is comprised of a container or tank to hold the nutrient solution, a platform that floats on the solution and holds the net pots in which the individual lettuce plants grow, and a pump to aerate the solution.

Germination and Transplanting

• Loose leaf, butterhead and Romaine or cos lettuce varieties can all be grown hydroponically. Hydroponic lettuce seeds are started indoors by planting them in a soil-less medium such as peat, perlite or rockwool foam cubes, keeping them moist as they germinate and start to grow. Seedlings can be transplanted into the hydroponic garden two to three weeks after germination. By planting a new crop every two weeks, gardeners can ensure a steady supply of fresh lettuce throughout the growing season.

Care and Considerations

• As a cool-season crop, lettuce does best when grown during the spring or late summer. Temperatures above 95 degrees Fahrenheit will cause the plants to bolt and develop a bitter taste. Lettuce also prefers partial sun, so placing the plants under a shade structure made of 50 percent shade cloth is a good idea for full-sun locations. Seedlings should also be protected from the wind as they will easily dry out in windy conditions. Inspect plants regularly for signs of disease and pests so that any issues can be identified and addressed before they become severe.

Harvesting

• Hydroponic gardeners can be enjoying a lettuce harvest as soon as 55 days after planting for head lettuce varieties. Loose leaf varieties are ready approximately 75 days after planting. Generally, heads of hydroponic lettuce are harvested with the roots attached. It’s also possible to harvest individual leaves by breaking them off from the outside edge of the plants, allowing the rest of the head to grow to full maturity. Once harvested, heads of lettuce can be held in the refrigerator for 10 to 14 days in a loose plastic bag. Leaf and butterhead lettuces can last as long as four weeks if separated into individual leaves and are fully dry when bagged.