How to Start Tomato Plants from Seed

Tomatoes are the most popular vegetable garden crop. Most gardeners buy seedlings for transplant, which works just swell. Starting your own tomato plants from seed involves a tad more diligence, but is more cost effective and in my opinion more rewarding. By growing your own seedlings you also have a much wider range of varieties to choose from, rather than the handful available from your local nursery or garden center.

Basics of Planting Tomato Seeds

With rare exceptions tomato seeds should be started 6-8 weeks before the last winter freeze date and transplanted into the garden 1 to 2 weeks after last spring frost. Germination time averages are 6-14 days, but of course this sometimes varies slightly depending on variety and growing conditions.

They are heat-loving plants that require a fairly long growing season. Optimal Germination temperature is 70 to 85 F. Once the seedlings emerge, slightly cooler temps of around 65F are acceptable. They are not tolerant of frost.

To get started you’ll of course need viable seed. Seed packaged for the current growing season is advisable as the older seeds get the lower your chances of achieving lift off / germination.

Planting Requirements

1. A warm location – prior to germination a warm location is needed to place your seed trays. After germination, once sprouts start breaking the soil you will also need sufficient sunlight such as under a sky light or on a sunny window. If this is not feasible than Grow Lights become necessary.

2. Light – The best results re achieved with grow lights. Early spring and Winter sunlight is not as strong as summer sunlight, there are fewer daylight hours. Insufficient lights early in the plants life cycle easily leads to less robust, scraggly plants. Grow Lights for seed starting are not all that expensive and a worthwhile investment for the avid gardener.

3. Suitable containers, such as cell pack starter trays, peat pots, or even old milk containers, even egg cartons and soda bottles so long as you have cut drainage holes into their bottoms. Do not use metallic containers such as old cans as the metal will interact with the soil and create undesirable effects. See: Unusual Seed Starters from Household Items.

4. Sterile potting soil for seed starting. It is not a good idea to use soil from your yard as you run the risk of introducing soil borne pathogens into your seedlings and insects into your home, they also drain poorly. Commercially produced potting mixes are sterilized soil. Many “potting soils” are actually soil-less mediums, but its best to choose one labeled specifically for seed starting.

Seed Starting Procedure

I. Fill your containers with your sterile soil, leave roughly 1/2 of head space at the containers top. The soil should be firmed down but not overly compacted.

II. Moisten the soil, do not saturate it just moisten it.

III. Place up to 3 seeds in each container on the soils surface. Anticipate that some seeds will not germinate, also be aware that you may need to thin out weaker specimens later on. Cover the seeds with roughly 1/4″ of potting soil – so you should still have 1/4 inch head space in your containers.

IV. Water lightly once the seeds have bee sown to ensure good seed-to-soil contact. Once again do not saturate the soil just dampen it.

V. Place the pots in a warm location, some people use heat mats which are helpful in some situations but not absolutely necessary.

VI. Keep the soil uniformly and persistently moist. Using a mister is a nifty idea as other methods can displace soil and seeds. I like to put plastic wrap over the pot tops to retain moisture.

VII. As soon as sprouts emerge remove any covering and place the pots under grow lights or in a sunny window.

VIII. If using a sunny window, the pots should be rotated on a regular basis in order to produce an upright plant rather than a lopsided one that grows into the sunlight. Grow lights should be adjusted to the appropriate heights and adjusted as the plants grow.

IX. Continue to keep the soil moistened until transplant day. hardening the seedlings a tad before transplanting is also a good idea. [See: Hardening Off Seedlings]. You also might want to consider leaving a fan blowing on the seedlings for at least several hours daily. Good air circulation reduces disease issues and acclimates the plants to the outdoor environment. See Part Two: Seedlings and Transplants