- Nutrient pH 5.5-6.5
- EC – 0.8-1.2
- PPM 560-840
Lettuce and other green leafy vegetables are among the easiest crops to produce hydroponically.
They thrive and produce abundantly in almost any setup and do not require meticulous care.
Lettuce can also be harvested in an ongoing basis, a few outer leaves at a time as it grows. When the outer leaves are removed, the lettuce head will rapidly produce more leaves to replace them. This practice is similar to “dead-heading” in flowers and herbs.
One “drawback” to growing hydroponic lettuce is that it matures so quickly, generally within a matter of weeks. That you will usually have more than you can possibly use – hope you enjoy a lot of salads. In hydroponic setups lettuce furnishes more edible produce per square foot than any other vegetable.
Lighting
Lettuce will grow vigorously with simple flourescent lighting. It would of course grow better with the more costly lighting designed specifically for hydroponics – such as HID and some of the new LED lights – but so far as cost effectiveness is concerned, from the point of view of the small scale grower – flourescent lighting will suffice. Related Article – Hydroponic Lighting
Lettuce has been known to bolt to seed with insufficient lighting, this causes it to be bitter and inedible. However, too much light will encourage algae growth in the water. You need a happy medium,if your lettuce bolts to seed throw it away and start again. If you get some algae growing in the solution, that’s not a good thing- but it can be treated. See – Hydroponic Algae Buildup.
Grow media and suitable Substrates include Oasis cubes and rockwool cubes, cell packs with a vermiculite-perlite medium.
Planting
It is best to start your seeds in cubes of inorganic material such as rockwool or even coco coir, not soil.
When they are ready to play with the big plants, place the entire plug into the hydroponic media bed. The roots will grow right on through. You can also start seeds directly in the setup. Seedlings are generally grown 14 to 21 days before transplanting to the hydroponic setup.
Seed Starting
Lettuce seeds become less viable as they age, germination rates decline incredibly. Be sure to use seed that is packaged for the current growing season.
1. Moisten the starter cubes.
2. Insert the seeds into the cubes holes. You.ll need roughly 5 seeds per cube, anticipating that some will not germinate and weaker ones can be weeded out later.
3. They should be placed on a tray and watered daily with straight water and no nutrient solution till the seeds germinate and sprout, which should only be a few days. After sprouting use 1/2 strength solution.
4. Once the seedlings are growing thin out the extra seedlings leaving only one of the fittest looking lettuce seedling in each cube. Some of the thinned out lettuce plants may be suitable for transplant elsewhere.
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.
Nutrients
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