Plant Starter Tray With Drainage Can Be Planted In Or Used To Hold Cell Packs. Drainage slots allow water to pass through. For best results always use a new tray when planting seeds to avoid spreading plant disease. Always use sterile seed starting mix. These trays work fine planted directly when rooting plant cuttings. If you are planting seeds, it is really much better to start with cell packs. The best way is probubly to start with cell packs 003128, transplant to peat pots, place the peat pots in 003099 so the water will drain away from them, place that in 41234 so the drainage will not run all over the place. When starting seeds and seedlings use a mister to water, do not pour water on the baby seedlings. 21" x 10.5" x 2.25".