In the past few decades, hydroponics has become a popular way to increase the yield of commercially grown vegetables and fruit. The idea of hydroponics is not new, however. In the Hanging Gardens of Babylon, plants were grown in a steady stream of water. Modern hydroponics got its start when Leonardo DaVinci noted that plants needed nutrients to thrive. Experiments in hydroponics advanced through the 17th century into the modern era. Today hydroponics isn't just for scientists and commercial growers. You can start a hydroponics garden right on your kitchen counter for winter basil, or in your greenhouse for hothouse tomatoes.
Fill a seeding tray with a soil-less mix such as perlite, peat moss or rockwool.
Soak the seedling tray uniformly with water mixed with a nutrient solution. The solution will contain all of the nutrients that the seedling would normally obtain from soil, including nitrogen,potassium and phosphorous. Pre-mixed solutions are low in nitrogen and high in potassium and phosphorous. A typical ratio for pre-mixed solutions is 4-18-38.
Sow the seedlings into the seeding tray by sprinkling them on top of the soilless mix.
Cover the seeding bed with ¼ to 3/8 inches of soil-less mix.
Water from above thoroughly with a watering can and a water and nutrient mix. The soill-ess mix should be as damp as a saturated sponge when you have finished watering. Water evenly to promote consistent sprouting and growth.
Cover the seeding tray with enough plastic polyethylene sheeting to completely envelop the tray and overlap the edges. The sheeting will hold in moisture. Place the tray under a grow light.
Check the seeding tray frequently to ensure that seeds do not dry out by lifting the corner of the sheeting and touching the soil. The soil should remain as damp as a wrung-out sponge.
Remove the plastic sheeting once seeds have sprouted to ensure that seedlings don't overheat.
Thin seedlings by pulling up the weaker ones as they grow larger. The stronger and more vigorous plants should be spaced far enough apart that they do not crowd one another. The spacing will vary depending on the type of plant. For example, vegetables such as lettuce can be spaced more closely than vines such as tomatoes.
Cut the dirt in the seedling tray into squares with a trowel and transplant the squares with seedlings into a rockwool cube as seedlings grow.