About Tomatoes
With an estimated 25,000 varieties, it's no wonder tomatoes are a top source of vitamins for Americans. Tomatoes come in a spectrum of colors—yellow, pink, purple, green, orange, rainbow, and the classic red—each offering unique ways to enjoy them. We often grow tomatoes for sauces and soups, but nothing beats the taste of a fresh, sun-ripened tomato to signal the arrival of summer. Part of the nightshade family, successful tomato cultivation relies more on maintaining night temperatures of at least 55°F than on daytime warmth.
When to Plant Tomato Seeds
Before planting, decide whether you prefer determinate or indeterminate tomato varieties. If you want a single, bountiful harvest for making sauces or preserving, choose determinate varieties like Roma or Ace 55. For a continuous harvest throughout the season, opt for indeterminate types such as heirloom tomatoes like Cherokee Purple, Black Krim, or Green Zebra.
Tomatoes thrive in warmth, so most gardeners don't have long enough growing seasons to start them from seed outdoors. Instead, start seeds indoors six to eight weeks before you plan to transplant them outside. Tomato seeds typically germinate within 10 days. The plants grow quickly, especially if kept warm and well-lit.
Be cautious when it comes to transplanting outdoors. If the plants are planted out too early, frost or a cold spell could easily hinder their growth or kill them. Tomatoes planted a little later in the season will quickly catch up to earlier transplants that have been stunted by cold.
While tomatoes are indeed heat-loving plants, nighttime temperatures are crucial for their successful growth. When nighttime temperatures remain steadily above 50°F, it's safe to begin hardening off your seedlings. By this time, your plants should be several inches tall with some branching.
To harden off your seedlings, start exposing them to the outdoors for gradually increasing periods each day, about seven to ten days before you plan to transplant them into the garden. Begin with a few hours in a sheltered location and gradually increase the duration and exposure to direct sunlight. After this transition period, your plants should be ready to thrive in your garden.
Where to Plant Tomato Seeds
To determine the best location for planting tomato seeds, consider the mature size of the plant. Generally, determinate tomato plants tend to be smaller than indeterminate varieties. For container gardening, consider smaller plants like Tiny Tim or Early Girl.
When your seedlings are two to three inches tall and have a couple sets of true leaves, it's time to transplant them into your garden or larger containers. Plant the seedlings deeper than they were in their pots, burying them up to the top couple sets of leaves. This encourages new roots to form along the buried stem, making the plants stockier and stronger—especially helpful if they have grown too tall indoors.
For optimal growth, space your tomato seedlings two to three feet apart in an area that receives full sun all day and has well-draining soil. Using a drip system is the best way to provide steady, consistent water to the soil without wetting the leaves, which helps prevent disease.
How to Plant Tomato Seeds
It's often more efficient to dampen the potting mix before placing it in the containers. Add water gradually and work it through the soil until the mix stays compressed in your hand without dripping but breaks apart when poked with a finger. Fill your containers with this pre-moistened potting soil, gently firming it until it's about an inch from the top.
Place two to three seeds per container and lightly cover them with soil. Keep the soil moist but not waterlogged. Once the plants start forming, you can increase the water slightly. Ensure they get plenty of sunlight and rotate them regularly to encourage even growth.
When it's time to transplant the seedlings outside, add stakes or tomato cages early. This will help the plants grow upright with support as they need it. Trying to fit a mature tomato plant into a cage later can be challenging and may result in broken branches.