|Preparing and Planting in Seed Flats|
Choose your sowing medium carefully. It should be porous and well drained, but absorbent and soft as well. Textured humus or compost is fine. You definitely should not use dirt from the garden, as it can bring in disease and weed problems, and seldom provides the best consistency or drainage for starting seed indoors. Please see "What is the Best Planting Medium to Use?" for more detailed information.
1. For each 5-1/2 X 7-1/2 inch flat to be filled, dip out four cups of growing mix and place in a plastic bag. Add 1-1/2 cups of water at room temperature.
2. Close the top of the plastic bag tightly and gently squeeze the moistened growing mix to help it absorb the water thoroughly.
3. Put the moistened growing mix into a seed flat and run a flat piece of wood (a ruler is good) over the top to level off the mix even with the top edge of the flat. Pat it down gently, but add more mix if the level goes lower than 1/4 inch lower than the brim of the flat.
4. Make shallow furrows one inch apart in the surface of the growing mix, using a pencil, your fingers, or a wooden label cut to fit the flat. Make the furrows 1/4 inch deep for small seed, 1/8 inch deep for tiny seed. Large seed can simply be poked into the medium without making a furrow, though you will want to keep them in lines for ease of transplanting. For extremely tiny seed like Begonia and Calceolaria, which are almost like dust, it is best to evenly broadcast them over the surface of the growing mix, since their size makes planting in rows impractical. If your seed are hairy or cottony, plant them as they are, hair and all.
5. Make labels for each kind of seed you plant, and be sure to include the sowing date. No matter how good your memory, it will most likely not be up to retaining all the information about every seed you’ve planted, and you will need the name and date of sowing to determine when and where to plant your seedlings out in the garden.
6. The size of the seed will make a difference in how you plant them, so please see Preparing and Planting in Seed Flats, pgs 2 & 3, to read about the treatment of tiny, medium, and large seed.
7. Water the flat from the bottom. Place the flat in a pan of water at room temperature (cold water can slow germination) until the top of the medium is very moist. Bottom watering in this manner helps to prevent seed being washed away by the force of sprayed water, helps minimize disease, and is one of the best ways to keep the planting medium evenly moist, but not overly wet.
8. Cover the flat with a clear plastic sheet, or place in a clear plastic bag. The plastic should not touch the surface of the growing medium, so you can use toothpicks, labels, wooden dowels, or other small supports to hold it above your tray.
9. Place where the seed are to germinate. Most seed require good light for proper seedling growth, but do not place in direct sunlight. A waterproof seedling heat mat will greatly improve the performance of your seed, and I really recommend having a thermostat to control the heat so you don’t inadvertently burn or stunt your seedlings.
10. As soon as you see the seed begin to sprout, remove the plastic covering and move to higher light – filtered sun light on a windowsill, or under a grow-lamp is ideal. Your little seedlings might benefit from a short transition to the brighter light conditions. Start with three hours a day in the brighter area for a couple of days and then add three more hours every two days until, at the end of 5 to 6 days, you have them acclimated to the brighter area.
Tiny Seed (Impatiens, Begonia, Petunia)
Medium Sized Seed (Salvia, Pansy, Cabbage)
Large Seed (Morning Glory, Sweet Pea, Zinnia)
NASA Seeds in Space
"Plants vary in their heat stress tolerance, not only from species to species, but also from cultivar to cultivar. In addition, unusual seasons-fewer or more hot days than normal-will invariably affect results in your garden, as will extremely dry or humid conditions," Dr. H. Marc Cathey, with Linda Bellamy, Heat-zone Gardening, How to choose plants that thrive in your region’s warmest weather.