1. Don’t plant too early. Some seeds sprout and grow quickly, and they can get leggy and weak if they have to wait too long to go outside. So, how do you know when to plant? Read the seed packet. It will tell you whether indoor sowing is recommended, and if it is, it will say how many weeks before the last frost date you should plant. Here is a great resource from the Old Farmer’s Almanac for determining planting dates: 2012 Best Planting Dates. Just enter your city or zip code for personalized results.
2. Label your flats. I know, you think you’ll remember, or recognize what comes up, but 6 weeks from now, I assure you there will be some confusion. Use a Sharpie on Popsicle sticks or tape to mark what went in where. Sometimes I tape a piece of the seed packet to the tray.
3. Cover your seeds. Many seed trays come with a clear plastic top. If you don’t have that, use plastic wrap. Covering your trays after planting helps keep moisture in, and it keeps the seeds a little warmer too. Mist or water very gently when needed.
4. Fight Disease. Once most seeds have sprouted, uncover the flat to let air circulate. Seedlings with too little air circulation are susceptible to damping off, a fungal disease that strikes quickly and rots stems at the soil line. It happens will little warning, and can wipe out your baby crop over night, so make sure you’ve got some air flow. It’s not a bad idea to run a fan gently in the room, just to keep the air moving. Thinning seedlings and watering properly will also help prevent damping-off disease.
5. Don’t crowd seedlings. Thin them ruthlessly, so they don’t have to compete for water and nutrients. It’s better to have one strong plant than 3 weak ones.
6. Add light. To grow straight, strong stems, your seedlings need 12-16 hours of daylight. That’s impossible at this time of year, without adding artificial light. There are lots of economical grow lights, and it will make a tremendous difference in the quality of your little plants.
7. Water gently. Preferably from the bottom, or mist the soil surface. This one can be a little tricky. Over-watering is another invitation to damping-off disease, but tiny plants can also dry out quickly if they aren’t watered. Check daily and add enough water to keep the soil moist, not water-logged.
8. Harden Off. Tender seedlings won’t tolerate an abrupt change to outdoor sunlight and wind. Put them out in a shady, sheltered spot, for a few hours, then bring them in. Slowly increase exposure over a week. That gives your little plants time to acclimate to sunlight, and grow stronger to withstand an all-day breeze. Then, if the weather forecast co-operates, move them to their permanent home.