Growing Lettuce Hydroponically
Nutrient pH 5.5-6.5 EC - 0.8-1.2 PPM 560-840
When roots begin to show and seedlings reach 2-3 inches tall, with 3-4 true leaves, Your seedlings are ready to leave the nest and enter into the setup. Note that if you decided to use transplants from soil be absolutely certain any soil clinging to the roots is washed off before placing the plants in a Hydroponic or aquaponic scenario.
5. Lettuce plantings should be staggered -roughly 3 week intervals in order to ensure a continuous harvest.
6. Lettuce requires relatively cool temperatures for germination. The pre-germination stage should be around 40 F. As soon as the seeds show the slightest signs of sprouting place them in temperatures of around 65 F.
For best results Lettuce should be grown rapidly. It requires high amounts of potassium to grow well. Some lettuce varieties are nitrogen sensitive and easily get leaf tip burn when nitrogen levels are too high.
Calcium and Magnesium sulfate are great for lettuce, but unfortunately are not part of the hydroponic nutrient mixes available, so must be added separately to the Hydroponic solution. Calcium and Magnesium deficiencies commonly occur simultaneously it is advisable to supplement your solution with calcium and magnesium [Cal-Mag]
Under warm conditions with high lighting lettuce can be forced to grow faster by using a high nitrogen solution.
Under lower light levels, such as fluorescent lighting, potassium and nitrogen levels should be reduced. Related Article - Hydroponic Nutrients
Hydroponic Crop Profiles