Start tomato plants from seeds indoors 6 to 8 weeks before your last frost. Starting your seedlings indoors while it is still cold outside extends your season for a crop that does not like the cold. Cool temperatures in early spring can stunt growth or even kill young seedlings. Start your seedlings indoors to improve your production chances and length of fruiting season.
Fill your chosen seedling containers with your favorite seed starting mix. Sow 2 to 3 seeds ¼” deep in each pot. Cover with soil and pat down lightly. Water well. Place the containers on a seedling heat mat or in room of 70 to 80 °F until germination occurs. When the seeds germinate, move them under grow lights. In our experience, this time of year there is rarely enough light to grow healthy seedlings even in the sunniest of South facing windows. Use a humidity dome, or mist the seeds daily for the first 7 to 10 days. When you start to see sprouts, remove the humidity dome. Check that your seedlings stay moist for the first couple weeks after sprouting. They have not developed many roots yet and will dry out quickly without your help. Water from the top down in the beginning, and then you can switch to soaking the seed flats in water, so the roots are watered from the bottom up, which helps develop strong roots. Check your pots every day.
When your plants are about 6” tall and your grow zone is out of danger of frost, you are ready to start hardening off your plants. About a week before you plan to transfer your plants outdoors, you need to gradually adjust them to outdoor temperatures. Gradually expose the plants to the sun, starting in a partially shaded area and slowly extend the number of hours the plants stay outside each day. Start with an hour or less per day and gradually increase from there.
Prepare your garden space. You want to use well-drained soil with a good amount of organic matter present. Mix in leaf mold or compost if you need to improve your soil consistency or drainage. Dig a hole about twice as deep as the height of your plants. It needs to be deep enough that you can plant your seedlings and only the top 1/4 of the plant will be sticking out of the ground. Place a scoop of organic matter such as compost or worm castings into the bottom of the hole. This will give your plant an extra boost, and also help keep the plant from going into shock from transplanting.
Take the plants out of their pots carefully and place them in the ground. Try not to disturb the roots during the transplanting process. Set the transplants deep enough so that the soil touches the first set of new leaves when you cover the plant with soil. Pat the planted area lightly. Be sure to remove all of the leaves that are at or below soil level. Tomatoes can catch diseases from their leaves making contact with the soil. Placing a layer of organic mulch around your plants will help keep soil from splashing up onto the leaves during rains which can help keep disease at bay.
Place stakes or trellises next to the plants at the time of planting. This will give the plants a support to latch onto as they grow and makes it easier to pick the fruit from the vines. Doing this early will keep you from accidentally damaging the roots later on, and once you plant outside, tomatoes can grow quite quickly. Trying to trellis a tomato plant after it’s already gotten big is a challenge.
You can fertilize the plants with fishmeal, chicken manure, or a premixed low-nitrogen, or a high-phosphorus organic fertilizer for the first time a couple weeks after planting outside. Your plant will have had a chance to put on some good new root growth at that point and a feeding can be helpful.
Water at the base of the plant to avoid developing mildew on the leaves. Sprinkle your plants with liquid seaweed and layer the compost directly on the soil around the plant. Depending on your soil quality, you can do this weekly to monthly for increase fruit production.
If you want to promote better growth and a higher fruit yield, pluck the suckers off of your tomato plant using your fingers when they appear. Suckers grow in the crotch between a side stem and the main stalk. Leave a few near the top of the plant to avoid sunscald.
Fruit should appear about 60 days after transplanting. Check the plants daily once they begin to ripen to ensure peak flavor. Gently twist the fruits and avoid pulling at the vine.