Planting tomatoes in your garden is easy. You've probably done it before and will again. The process is basic, but there are a few things you can do to get the most out of your plants.
The most important aspect of planting tomatoes is doing it at the appropriate time of year. Tomatoes are a warm-season plant originally from tropical regions and therefore can't handle cold weather at all. Waiting to plant until two weeks after your Last Frost Date is very important. The warmer the conditions, the better for the tomatoes.
Air temperature should be consistently above 50F (10C) degrees; that includes night time too. Soil temperature should be at least 60F degrees and ideally around 70F; roots will not grow below 50F soil temperature. If you plant with the air or soil temperature too low, you can expect issues with your plants. Growth and fruit may be sparse, they may become more susceptible to disease and pests, and they may be stunted and small. Waiting just one extra week until conditions are right can make the difference between success and failure. If unexpected cold temperatures hit after planting, it's important to cover the plants with a blanket, tarp, or plastic sheet to retain warmth.
The location of your planting is the next most important component. Tomatoes need sun. Full sun, for the whole day. Seven hours of full sun is a minimum. Even a little shade can make the difference between abundant fruit production and a sparse harvest so put tomatoes in the sunniest spot in your garden.
Plant selection is important, but not critical. There are two different types of tomatoes, determinate and indeterminate. Determinate tomatoes are often called "bush" tomatoes. They grow until they begin to put on their flower clusters and then they stop growing taller. Determinate tomatoes tend to mature earlier, set fruit earlier, and produce all of the fruit at about the same time for harvest. Indeterminate tomatoes will continue to grow throughout the season and are what we think of as tomato vines. They grow longer, mature later, and will continue to produce flowers and fruit until the first frost in fall.
The cultivars of tomatoes are numerous. You can get tomatoes that mature in as early as 45 days to as many as 80 days; that's the time it takes to produce fruit after planting outside. "Early Girl" is a popular cultivar that produces fruit close to the 45-day point, "Better Boy" and "Celebrity" produce fruit mid season at about the 60-day point, and many heirloom tomatoes like "Brandywine" or "Mortgage Lifter" take a full season of 80 days to bear fruit. When you select tomato plants, look at the plant tag or ask a nursery worker to find out how many days it will take for tomatoes to ripen. Compare that to your growing season length and select one that gives you plenty of time to enjoy your harvest.
With the plant in the ground, water it well. Don't allow the soil to dry out after you place it in the hole. If you're planting a number of plants, this means watering each one after it's in the ground. Expect to use between a quart and a gallon of water per plant, depending on its size. Until the root system is fully established the soil should remain moist. Moist, not saturated. A primary reason for tomato plant failure is overwatering. Even though they have a tropical origin, tomatoes don't like to be waterlogged.
At some point you'll need a stake or cage to help support the plant. You don't need to worry about that at planting; I usually do that a few weeks after planting. You'll also want to mulch the area with straw, grass, or pine needles, but that can wait a week or two as well.
The last step, if you didn't do it earlier, is to mark the plant. Use some type of tag, stick, flag, or marker to allow you to identify the plant. Especially when planting a number of different cultivars of tomatoes, it's nice to know which ones are which. At the end of the season you'll know which plants did the best. This allows you to grow the successful ones again.
That's all there is to it. Your plants are in the garden and on their way to producing a bumper crop. There are still many more things to do until harvest and I'll cover those in the months ahead.