Many of us get a good feeling from planting seeds and watching them grow when outside it is still dark and cold. But inside, we are planning for spring planting. We can start the varieties we want—perhaps a favorite is not available locally as a transplant or as seed; we can raise it ourselves from seed!
Most everyone I know has good luck starting seeds in a sterilized seedling mix. It may be difficult to find an organic seedling mix; and it must be sterile or seedlings might dampen off from fungi present in the air and abundant in unpasteurized soil mixes. A mix I make is soil free: 6 parts sterile (pasteurized)peat moss + 3 parts fine perlite + 1 part washed coarse sand. If you are unsure if your mixture is sterile or not the mix may be heated in an oven at 160 degrees for one hour. Do not allow the mix to heat above 180 degrees. A mixture including compost would need to be sterilized by heating to use for seedlings.
Several types of containers might be used to start your seedlings. In the first picture above, I used a milk carton cut laterally, providing two useful containers. Shown are pepper seedlings. Peat pots work well for plants that are difficult to transplant, because they minimize transplant shock and biodegrade into the soil. Be sure to keep them quite moist once planted, because if the peat pots become too dry, roots will not penetrate the container. Some plants that benefit from being raised in peat pots and are difficult to transplant are: portulaca, nasturtiums, sunflowers, poppies, eggplant, squash, cucumbers, melons and pumpkins. Peat pellets also work, but they sometimes are so hard that roots have difficulty growing in them.
Timing is another important factor in raising seedlings. Your transplants should be big enough to mature and produce in your season, but not too big, or they will not take off well and will take up a lot of room in the house. Here is a basic seed planting guide, categorized month-by-month, of which seeds to plant at what time for success in northern climates of 100 to 170 days. (Adjust timings to your local climate):
In January plant impatiens, begonias, geraniums and salvias. Late January or early February is a good time to start eggplant, peppers, onions, petunias and pansies. March is probably the best month to start cole crops (brassica family). April is a good time to start tomatoes and balsam; late April or early May for pumpkins, squash, melons, cucumbers, and nasturtiums.
Florescent grow lights with an adjustable chain are a great help in starting nice seedlings; the lights can be lowered with the chain to keep the newly emerged seedlings in bright light. This will prevent your plants from getting “leggy”. Temperatures vary for germination: cole crops about 65 degrees, onions about 70, tomatoes about 75 and eggplant, peppers, squash, melons, cucumbers and nasturtiums about 80 degrees.
Make sure your seedling mix is not too wet. Some seeds like to germinate on the dry side, such as tomatoes and peppers. I cover my newly-planted seeds with plastic wrap, but check them twice daily for moisture and rotate them if necessary. Once the seeds are just up, I loosen the wrap (a little more each day) to harden the babies off to the air. Grow your plants on in cooler conditions than you germinated them and they will grow stockier. A cold frame is just about the best place you can put them if it is not too cold outside. In a south-facing cold frame the soil will remain warm at night, and daytime venting will give the plants fresh air. Keep shade cloth handy if it tends to get too hot during the day in your area. This is a common occurrence in dry, sunny climates with warm days and frosty nights. The second picture above shows newly transplanted seedlings in a cold frame vented for the day. A cold frame will harden-off your plants before planting out. Don’t forget to place open-ended containers around plants as you place them in the garden to deter cutworms. Good luck!