Hydroponic Lettuce Farm

 I'm growing lettuce indoors hydroponically as an experiment of actual food production.

Materials:

• 48" LED shop light.  $19 at WalMart
• Electric timer.
  
• 12 32oz mason jars, regular mouth, with rings and lids. $30 at Amazon
• 2" net cups.  Pack of 50.  $10 Amazon
• Rock wool growing cubes
• Grow Big nutrient solution
  
• 2 one-gallon water jugs for mixing nutrient solution
• Paper sleeves to cover the mason jars
• Clear plastic storage container with lid, shoe box size.
• Lettuce seed, Basil seed
  

Week One:

1.  Begin by mixing up a 1/2 gal of nutrient solution at half strength.  Soak 12 rock wool cubes in this weak solution in the plastic storage container, which is now serving as your germination chamber.  When the starter cubes are fully saturated, leave the cubes standing with their feet in the water, just the lower 1/8th inch.  Make sure the solution does not come up higher and flood the seed.

2. Place 1-2 seeds in each cube. The last two cubes will have basil instead of lettuce.  (Keep your unused seeds in a zipper bag in the refrigerator).  Replace the lid of the container to maintain humidity around the seeds.  Lettuce seeds germinate at cooler temperatures so try to place your box in a cooler location out of direct sunlight until the seedlings emerge.  

Germination will take roughly 7 days. Check your germination chamber regularly to make sure there is adequate nutrient solution, so that your seeds and seedlings do not dry out.

Week Two

3.  Once the seedlings emerge, continue to grow them in the storage box until the first true leaves emerge.  This will usually take an additional week, leaving our timeline at 14 days.  During this time continue to add the weakened nutrient solution so that the cubes stay moist, but not flooded.

4.  During this week prepare the materials for the next stage:

• Suspend the 4' LED light over your growing area on its adjustable chain.  Set the electric timer for 18 hours on and 6 hours off.
  
• Arrange 12 mason jars with 12 net cup lids in the growing area
• Mix up additional full strength nutrient solution and fill each jar so that it barely touches the bottom of the net cup.
• Prepare the paper sleeves that will cover the jars and exclude the light, preventing algae from growing in the water below.  Fold the sleeve so that it has four distinct sides as it wraps around the jar.
  
• On each sleeve, Number each of the four sides (Week 1, Week 2, Week 3, Week 4)
• On the first side, write the date of transfer from the germination chamber to the jar.
• Then, determine what the date will be 3 months later and write that under the transplant date.  This is the expected productive life of this plant, after which we will need to replace it with a new one.
• The seedlings will remain in the plastic box until you see roots emerge from the cube.
  

Week Three

5. Transfer each young plant from the germination chamber to the net cup in the mason jar.  Pack a little filling material around each rockwool cube so that it fits securely into the net cup. (This could be additional rock wool, or hydroton balls, or glass pebbles or pool noodle bites.)  The tips of the emerging roots should reach into the nutrient solution.

Continue to grow in their new mason jars for an additional week.

Week Four

6.  The lettuce and basil plants are beginning to reach a mature size.  Let them grow an additional week undisturbed.

Week Five

7.  This marks the beginning of the harvest period.  Arrange all the jars so that "Week 1" is facing you.  To harvest, use scissors and snip off one leaf on the side facing you. Start with the bottom and outer-most leaves.  Initially, these first leaves will be on the small side, but the plant will continue to grow as the harvest continues.

Week Six through Eight

8.  At the start of the week, turn all the jars one quarter turn so that "Week 2" is now facing you. Then, harvest a leaf from each jar from this new side.  You will gather 10 or so lettuce leaves and 2 basil leaves for your salad.

Each subsequent week, you will turn the jar and harvest a new side.  This gives each trimmed side 4 weeks to recover and put out new leaves.

Remember that it took 4 weeks to bring a new lettuce plant into production.  We marked the end of production date on each jar.  So 4 weeks before that end date, you will need to get out the germination chamber and start a new set of seeds in rock wool

9. When the time comes, instead of snipping only one leaf, harvest the entire plant and clean out the net cup.  Replace the rock wool with a new transplant from the germination chamber.  Replace the nutrient solution with a fresh batch and update the sleeve with the new dates.

At that point, you will be able to continue the weekly harvest rotation.