Start tomato seeds indoors 6 to 8 weeks before your last frost date. Use a seedling heat mat or start your seedlings in a room kept at 70 to 80 degrees F, to ensure that the soil is warm enough for good germination. Make sure to place grow lights over your seedlings as soon as they emerge. Tomatoes are sun-loving, warmth-loving plants, and in our experience, even a sunny south-facing window won’t give these plants enough heat or light to thrive during the late winter-early spring months. Once your tomato seedlings are at least 6 inches tall, and the danger of frost has passed, begin hardening off your plants by bringing them outside for increasing periods of time each day. Allow at least a week for hardening off before transplanting outside.
Choose a location with full sun for your tomato plants, and prepare the soil by mixing in plenty of compost. It’s also a good idea to add a scoop of compost to the bottom of each hole as you transplant the seedlings. Plant your tomato seedlings deep - at least up to the bottom branches. All of the stem that is underground will sprout roots, strengthening the plant. Remove all of the leaves that are at or below soil level, so that no leaves touch the ground. Leaves in contact with soil is the most common way for tomatoes to catch diseases. Mulching around your plants also helps prevent leaf to soil contact. Place stakes or cages around your tomatoes at the time of planting, to make trellising easy as they grow.
Make sure your tomato plants get about an inch of water per week, but don’t water every day, and always water from the base of the plant. About two weeks after transplanting, your tomato plants will benefit from a high-phosphorus, low-nitrogen organic fertilizer. As the vines grow, pinch off the “suckers,” the smaller branches that sprout from where each larger branch meets the stem. This promotes an open growth habit for good airflow. About 60 days after transplanting, start checking your tomato plants daily for ripe fruit. Always harvest by gently twisting the fruit, to avoid damaging the stem as you pull them off.
Tomatoes (Solanum lycopersicum) are primarily self-pollinating because of the structure of their flowers, making them a good choice for a beginning seed saver. Tomatoes of different varieties typically need to be separated by just 20 feet to ensure pure seed. To harvest your own tomato seeds, just scoop the seeds out of a few fully ripe fruits. Try to choose fruit from plants that have desired characteristics - vigor, early production, etc. Put the seeds along with the gel-like substance that surrounds them in a jar with enough water for the seeds to float. Attach a coffee filter or paper towel over the top with a rubber band to keep out insects and allow the container to breathe. Then leave the jar out on the counter at room temperature for 2 to 3 days to ferment. Fermentation is complete when the seeds have sunk to the bottom of the jar, and there is a light layer of white mold on top of the water. Decant off the floating mold, then pour the seeds out into a fine mesh strainer and give them a thorough rinse. Lay the clean seeds out in a single layer on a paper towel to dry. Once dry, store them in a sealed container in a dark, dry, and cool location. Note: the fermentation process may sound a little gross, but it’s necessary! In addition to physically breaking down the jelly coat around each seed, it also breaks down chemicals found in the fruit that inhibit germination.