Pre-soak rockwool cubes in water adjusted to a pH of 4.5 for 24 hours, then drain.
Plant your own tomato seeds in your pre-soaked rockwool cubes. Starting your own seeds prevents pests or diseases that may ride in on nursery plants.
Place the planted rockwool cubes in a nursery tray with a plastic dome and set it in a warm, moist environment. A temperature of 68 to 77 degrees Fahrenheit is ideal.
Move seedlings into a light source and remove the dome as soon as they sprout. In your basement, this light source can come from a metal halide or fluorescent grow light.
Provide at least 12 hours of light per day. Seedlings that don't receive light as soon as they sprout may bolt or become leggy in search of light.
Protect the roots from the light in order to prevent damage or root death.
Transplant your seedlings into your hydroponic system once the first true leaves appear and the roots start growing through the bottom of the starter cubes. This usually occurs in 10 to 14 days.
Increase the light levels gradually by moving the grow lights an inch or two closer to the plants every few days.
Provide your basement hydroponic tomatoes 16 to 18 hours of light and 8 hours of total darkness per day to encourage maximum fruit production.
Monitor the pH level of the nutrient solution in your system closely and use adjusters as needed to keep the pH at 5.8 to 6.3. Small fluctuations in pH levels can cause nutrient deficiencies and plant damage.
Maintain a daytime temperature of 72 to 78 degrees Fahrenheit and a night temperature of 60 to 65 degrees. Tomatoes grow best with this temperature differential between day and night.
Prune and stake your tomato plants as needed. When pruning, remove the side shoots and suckers which grow between the main stem and the leaf stems; this will make your plants more efficient by cutting down on unnecessary use of nutrients for the extra shoots.
Pollinate your basement tomatoes manually by gently shaking the flowers or by dabbing a small paintbrush or cotton swab on the stigma of each flower. You'll need to pollinate your tomatoes yourself since they won't have access to bees or birds to perform this task.
Leach the growing medium by rinsing it with twice as much pH-balanced water as the container would hold when empty. Perform this task every time you change the nutrient reservoir in your system to clear the growing medium of toxic salt buildup.
Observe your tomatoes closely for any changes; catching nutritional disorders early is critical to saving your plants.
Leach the growing medium with clean water and change the nutrient solution if any signs of nutrient deficiency appear.
Check the color of the leaves; yellow leaves may indicate that the nutrient solution is too weak or the pH is too high.
Watch for curled-up leaf tips or red stems; these signs may indicate a magnesium deficiency caused by a nutrient solution with a pH that is too low.
Watch for flowers that fall off before setting fruit; this may be caused by a potassium deficiency.
Look for leaf tips that are curling under; this may indicate that the nutrient solution is too strong. If this occurs, add water adjusted to a pH of 6.0 to the nutrient reservoir to dilute.