Before we experience the ecstacy of vine-ripened tomatoes, we need to acknowledge the agony. It's real and we need to review it.
1. Tomatoes are (probably) natives of Peru where several wild varieties remain. Whatever their history of wandering from culture to culture about the world, the fact remains that they prefer a long growing season and sustained temperatures that range from 65 degrees at night to around 80 in the day. Our growing season (usually without frost) is from about May 15 to September 20th. That would suggest that we look for tomato varieties usually described as "short season". Short season tomatoes are usually beginning to ripen or ready to be picked in 55-60 days.
2. Tomatoes like to have their roots in warm (at least 60 degree) soil. As gardeners we need to remember that for the soil (kept cold by low daytime temperatures and moisture in the soil) to be at least 60 degrees we need not only warm days but also warm nights. The best way to know the soil's temperature is to USE A SOIL THERMOMETER. Fortunately these are available inexpensively ($10 or so) at area greenhouses.
3. Tomatoes are fairly fussy about blossoming in very hot weather. Bill Keck, former Pennington County Extension Horticultural Educator, writing in The Rapid City Weekly News in 2008 stated, "Tomatoes often produce more flowers at high temperatures, but above 85 degrees F. pollen production is impared and fruit set is decreased. Tomatoes will drop blossoms prematurely if temperatures are less than 55 degrees F. or above 95 F." At this same point, 95 F. Keck states, "At temperatures above 95 F. the fruit does not increase in size and will not color properly." On the lower end of the thermometer, the plant freezes (the liquid in the plant cells) at 32 F. and can show signs of frost damage at 40 F.
4. Don't be in a hurry to get the tomatoes into the ground. Most authorities state very clearly: plant into the garden about two weeks after the last frost date. (Do the math: two weeks after May 15 is the first of June. Wait a week longer if the spring is cold.) Always plant in warm soil (which you have determined is 60 F. by using a thermometer!).
5. Tomatoes require carefully prepared soil. Use well-drained soil high in phosphorous with planty of decomposed organic matter (compost, compost, compost.) Dig extra deep holes. Place a handful of organic matter in each hole. If the plants are still short (5-6") position the plant deep in the hole so that their first set of leaves is just above the soil level. New extra roots will grow along the buried stem. If the plant has become "leggy" then pinch off all but the top 3-4 stems of the tomato and lay it in a planting ditch, bending the top ever so gently so it is vertical above the ground. The buried stem will root vigorously.
6. Spoil them a bit. Always use warm water on transplants to reduce shock. Water deeply and frequently until well established then taper off a bit. Keck describes the watering protocol as follows: "On average tomatoes require about 18 inches of water to produce a good crop. Since rain is not evenly distributed throughout the growing season, irrigation (supplemental water) is required. Wetting the soil 8-12 inches deep will require 1 - 1/2 inches of water weekly which is equivalent to 5-7 gallons per week per plant. Avoid overhead watering. Many persons will mulch around tomato plants with old hay or straw to avoid backsplash from the soil reaching the plant foliage, a frequent cause of disease problems.
7. Keep them looking good. Most persons set the tomato cage or other supports into the ground immediately after planting the tomato. You will want to keep the tomato well supported. Remember that a DETERMINATE tomato is one that grows to a specific size, fruits almost all at once and then dies. An INDETERMINATE is one that continues to grow and produces fruit at all stages of maturity until killed by frost. You will also want to remove side shoots in the leaf axils (the 'armpit' of the plant between a main stem and a side branch). When the plants are about 3' tall, remove some of the old, lower leaves to improve air circulation at the base. Pinch back the top of the plants a bit when they reach the top of the supports to encourage flowering and fruit.
8. Pay attention to their nutritional needs. Bill Keck states, "A new transplant should receive a starter fertilizer high in phosphorus to encourage good root development. One tablespoon per gallon of water of a 10-30-10 starter fertilizer is a good solution. Fourty days after transplanting, apply one tablespoon of a nitrogen only fertilizer like ammonium nitrate, 34-0-0- or a lawn fertilizer that does not contain a week killer IF plants appear tight green in color. Then 60 days after transplanting (corresponding to fruit development) apply one tablespoon of ammonium nitrate per plant 6-8 inches from the stem and water well. Repeat the process two weeks later. This will increase the tomato fruit size in later harvest and keep the plant productive.
9. Tomatoes like to choose their friends. Authorities suggest that any of the following be planted next to - or in the pot- with your tomatoes: chives, onions, parsley, asparagus, marigolds, nasturtiums or carrots. DO NOT plant them near pototoes, kohlrabi, fennel or cabbage.