When growing a large number of bedding plants, space is at a premium. It is often easier to start small, fine flower seeds in large trays, or flats, then later transplant them into individual pots. Instead of a separate pot for each plant, using cell packs saves space and money. Cell packs are thin pots attached to each other. Several cell packs easily fits inside a planting tray, which is used to catch excess water run-off. Plantable peat cell packs are also available for seedlings that don't do well with root disturbance.
Sterilize the cell packs before transplanting if they have been used before. Mix 1 part bleach with 10 parts water. Rinse each cell pack in the bleach solution then rinse with clear water.
Fill each cell with moist potting mix. Use a commercial soil-less mix or make your own by mixing 1 part peat moss, 1 part compost and 1 part vermiculite.
Transplant into the cell packs once the seedlings have produced their second set of leaves, known as true leaves. Scoop the seedling out of the soil with a spoon, taking care to scoop under the root. Steady the seedling by lightly grasping the leaves, not the stem.
Set the seedling into a cell. Plant it to the same depth it was at in the tray. Water around it lightly to push out any air pockets around the roots.
Keep the soil moist at all times. Use a quarter-strength liquid fertilizer with one watering weekly.
Keep the cell packs under grow lights for 12 hours a day until ready to transplant outside. Adjust the grow lights so they sit 3 to 4 inches above the top of the seedlings.