How to Build Your Own Hydroponic Seed Starter

Fill the tray loosely with perlite. This serves to keep the seedlings stable and moist. Leave enough room that you will be able to add the rock wool cubes to the tray.

Place the rock wool cubes in the perlite, leaving an inch of space on all sides of each cube. Fit the cubes down into the perlite but do not allow the top of the rock wool to be covered.

Pour a small amount of the half-strength hydroponic nutrient solution into the tray. It should be approximately ½-inch deep. This will keep the environment moist, essential for germinating seeds.

Plant one to three seeds in the concave area of each rock wool cube. Cover the seeds with some of the rock wool. You don’t need to use much. This will protect the seeds and help to keep them in place. When the seeds sprout they should be thinned so that the single strongest seedling is left in each cube.

Cover the tray with a sheet of dark plastic. Many seeds do best when started in a dark environment; plus, the plastic will help to keep the environment humid.

Set the seed tray in a warm place, about 70 to 75 degrees F. On top of the refrigerator works well, or any other location where they will get enough warmth to germinate without becoming overly hot.

Mist the seeds every day, using half-strength nutrient solution. The rock wool cubes should be damp but not overly wet, since too much moisture can cause the seeds to rot.

Remove the plastic once the seeds have germinated, and place the tray in a well-lighted location. Leave them there, continuing to water them with the nutrient solution, until they grow big enough to be transplanted, and then move them to their final location.