Starting vegetables indoors is a rewarding experience. The vegetables get a solid and early start to their lives, and gardeners are able to reap the produce much faster than if they planted the tomato seeds directly into the ground. Tomatoes love heat and light, so in a shadier or cooler garden it is important to get a head start on growth by starting seedlings indoors when the ground is still too cold to plant tomato seeds. However, care needs to be taken to keep these tomato plants seedlings safe as they transition into the outdoors.
Plants naturally reach for the light, and if they do not find it they continue to reach, even if this means growing unwieldy stems. This is called getting leggy. Tomato plants are a sun-loving plant and they can get leggy if they are not exposed to intense sunlight when they are indoors. If you are using a grow light, place the plants as close as possible to the light and rotate trays so that all of the plants get equal amounts of light. Encourage tomato plant seedlings to develop strong, tough stems by blowing on or touching the tomato plants as the seedlings grow.
Plant tomato seedlings outdoors at least two weeks after the date of the last frost. This ensures that the ground and air are warm and that the tomato plants are able to access water easily.
Why harden off seedlings? Hardening off is the process of moving plants into the garden environment slowly so that they adjust to the more variable world of the garden. Seedlings are raised in a warm, light, and sheltered indoor environment. In the garden, there is more wind and rain and the temperature changes much more rapidly. This is why it is prudent to give tomato seedlings some time to get used to being outside.
Around the time of the usual last frost, begin to transition your tomato seedlings outdoors. This is the perfect time to use an outdoor but somewhat sheltered area like a deck to get the seedlings adjusted. Every day, bring the tomato seedlings to this sheltered location for a few hours in the early morning or the early evening when it is not too hot and not too cold. Gradually increase the time that the seedlings are outdoors and expose them to the wind, rain, and temperature changes. Watch the reaction of the seedlings, and if they begin to show signs of ill health, keep them indoors for another day or two before bringing them outside again.
When the tomato plants are ready, remove them from their containers and place them in damp, fertilized ground. Support them with tomato cages, stakes, or other support structures to keep them upright. Water the plants regularly and watch them to see whether they survive. If they do not, learn from the experience and next time you can change the way you introduce your tomato seedlings to the outside world.