(originally posted Feb. 28, 2012)
Getting a head start on your garden can be a fun and easy project. Starting seeds early gives you more time to enjoy flowering plants, and lets you harvest your first vegetables sooner.
Many seeds can be started indoors-the seed packet should tell you the right time to sow, usually noted as how many weeks before the last expected frost. As a rule of thumb, tomatoes are started 6-8 weeks before the last frost, peppers 8-10 weeks, onions 8-12 weeks. Flowers vary widely from 4-12 weeks.
Use a good quality seed starting mix. Regular bagged potting soils often contain added fertilizer, which is detrimental to seeds starting, supplying too much food for the young plants that they cannot handle. Seedling soil also needs to drain well, yet retain enough moisture for delicate seedlings. Digging soil from your garden to start seeds should be avoided as it often contains diseases and pests that can proliferate to the point of harming young seedlings. Won’t those same problems be present once you transplant seedlings into the garden you may ask? Yes, but the seedlings will have grown stronger, and the natural balance of “wild” soils keeps harmful diseases and bugs in check.
You can use any clean container to start seeds; recycling egg cartons and yoghurt containers as seed starters is popular and fun when you’re growing seeds with kids. (And here's another great idea we just found.) You can also get pellets of peat moss that expand into plantable mini seed pots or pots formed from (deodorized!) cow manure, both of which can be planted directly into the garden when the seedlings are ready. If you start in small containers it may be necessary to transplant seedlings into a larger container before they’re ready to go into the garden. In that case, choose a container about twice the size of the original and handle the seedlings gently. If you reuse containers previously used for plants, sterilize with a 1:9 bleach/water solution to kill any pathogens clinging to the container.
Supplying additional light by using fluorescent fixtures can help the problem of skinny, stretchy seedlings that eventually topple over and die. For maximum effectiveness, they should be placed 1-2” above the seedlings once they germinate, and raised as seedlings grow to keep a 1-2” distance from the leaves. Lights should be on for 14-16 hours per day.
One step often forgotten is “hardening off” the seedlings for at least a week by moving them outdoors during the day to a sheltered location that gets filtered sun and little wind. Gradually increase the time spent outdoors. This reduces shock when transitioning from indoor conditions to outdoor conditions.
A final note-sometimes seeds will indicate that they are best sown directly in the ground. Often this is because they transplant poorly, or grow poorly in indoor conditions, resulting in a weaker plant overall. As tempting as it may be, resist the urge to start these seeds early-you’ll probably have to re-sow anyway to get a quality plant.