In most climate zones winter arrives before tomato plants can finish their fruiting cycle. To provide longer period of vegetation for your plants you can start the tomatoes from seed adding a few weeks to their season of growth.
You could buy the seedlings started by someone else, but you would miss some of the benefits. When growing tomatoes from seed yourself you save money and you can cultivate your favorite heirloom variety, saving tomato seeds every year and starting them in spring.
First of all you need viable tomato seeds. The seeds you obtained this year or these collected last season should be fine. If you have doubts about their quality, perform the seed viability test. When less than 50% of your seeds sprout in time either use the fresh ones or sow them more thickly.
You need the planting substrate, preferably a special potting mix. If you use garden soil, add compost and sterilize it to kill pathogens.
What about containers? Special seed starting kit with a cover and heater is a convenient choice. Any plastic pots can work, as long as you provide the proper drainage. Making holes in the bottom of the containers to let the water out does the trick. Then prepare the piece of plastic foil for a cover.
Tomato seeds require warmth to germinate. When your home is cool consider using a heat mat with a thermostat to provide correct temperature for sprouting. The last item helpful with starting tomato plants is a spray bottle for watering the seeds.
The perfect moment for transplanting tomatoes to your garden comes two weeks after an average last frost date in your area and the seedlings after germination should grow an eight weeks in the pots. Therefore, start growing tomatoes from seed about six weeks before the last frost date in your area.
Fill the pots with the soil or potting mix and pour water into the bowl letting the soil soak. When you use the potting mix, work it with water till it's moist but not soggy. If you plan to transplant the seedlings to the larger container, sow the seeds thickly.
Do you sow in the final container before transplanting outside? Then make sure to provide enough space between the plants. Sow thinly or the shoots will compete with each other. Approppriate space between seeds is about 1 inch.
Cover the seeds with a thin layer of soil and cover with the transparent foil or plastic dome. Optimal temperature for growing tomatoes from seed is 21-27C (70-80F) , so keep them in the warm place or use the heat mat.
You will notice germination in about a week. When you can see the sprouts, partially remove the cover and let the air circulate.
Make sure to keep the sprouts in a warm place - if you were using a heat mat, continue. Young tomato seedlings need a lot of light, so the best place for them is a heated greenhouse or a glass room.
When you keep them at home, choose the lightest spot. However, avoid direct sunlight. If the seedlings keep bending towards light, room is to dark for the plants. Consider obtaining the Grow Light System to provide enough light, as elongated seedlings are weak and may die.
Keep the soil moist, but not waterlogged. Let the it soak from the bottom or use the spray bottle to avoid damaging tiny plants. After a few days remove the cover, as too much humidity leads to fungal diseases.
In case you were sowing seeds thickly, transplant the seedlings to the larger containers when they develop the first pair of true leaves.
You can avoid any problems with growing tomatoes from seed if you provide correct moisture of the soil, enough light, warmth and air circulation.
Place the pots with growing tomato plants outside in the shade for a few hours every day. After a few days you can leave them overnight. Then start putting them in the sunlight. For transplanting dig holes 1,5 - 2 feet apart. Mix in some compost and plant the seedlings. Water afterwards.
Growing tomatoes from seed is easy if you start the plants at the right time and keep light, temperature, moisture and air circulation at correct levels. See these tips for more information on growing tomatoes after replanting them outside.