Begin with Bonnie Plants
Bonnie plants leave our greenhouses with healthy foliage and well-developed roots. Water the plants well a few minutes before planting to be sure roots are moist.
Prepare the Ground
Loosen the ground to create a welcoming bed for roots to grow. Add agricultural lime according to the results of your soil test and add 3 or 4 inches of compost or other organic matter, especially in clay or sandy soils. For more about liming, see "Why does pH Matter?" THEN DIG A HOLE THAT IS AS DEEP AS THE PLANT IS TALL BECAUSE YOU ARE GOING TO BURY 80% OF THE PLANT.
Slip Plant from Pot if in Plastic
Gently remove the plant by slipping the plastic container from the root-ball. Don’t tug on the plant stem; this can sever it from the roots. If the roots are growing out of holes in the bottom of the pot, tear or cut them away and squeeze and twist the pot as necessary to work it from the roots. IF YOUR PLANT IS IN A PEAT POT, DON'T REMOVE IT. THE PEAT POT IS DESIGNED TO BE PLANTED AND WILL SOON BIODEGRADE INTO THE SOIL. Just tear off the bottom half of the peat pot to make sure that roots are in instant contact with the soil.
Untangle Roots (plastic pots only)
If roots at the bottom of the root-ball are growing in matted circles, gently break them out of the mat in two or three places, but don't tear them completely away from the root-ball. They should be dangling. This may seem harmful, but it helps direct overgrown roots into their new garden location. If the roots are not matted at the bottom of the pot, or if your plant is in a peat pot, skip this step.
Bury 80% of the Plant
Set the plant in the hole deeply enough so that 80% of it is buried. Laying the plant on its side is okay, so long as you angle it so that very top remains above ground. Roots will sprout all along the buried stem to make a stronger plant. You can pinch off the lower leaves if you prefer, but it is not necessary.
Fertilize
Sprinkle fertilizer on the pile of soil that will go back into the hole. Use a balanced fertilizer such as 10-10-10, or a timed-release product, which is more expensive but lasts longer and doesn't leach. It is best to fertilize according to recommendations from a soil test, but if you don't have that, apply about 1/4 cup of 10-10-10 or 2 tablespoons of timed-release 17-17-17 per plant. Or, use an organic fertilizer at the rate recommended on the label.
Work Fertilizer into the Soil
Work the fertilizer into the soil as you backfill the hole.
Bravo! Your Plant Is Almost Ready to Grow
When you’re done, 80% of the entire plant will be buried; only the top of the tomato plant remains above ground.
Water Well
Water thoroughly. This is very important to help settle the soil and start the plant. This is a good time to use a liquid starter fertilizer such as fish emulsion (a popular organic food) or a soluble plant food such as 20-20-20 (a popular conventional formula).
Consider a Soaker Hose or Drip System
This step is optional but recommended. Place a soaker hose or drip irrigation system in place for watering. This conserves water, and very importantly, helps keep the foliage dry. Wet foliage encourages diseases, which are the biggest challenge to growing tomatoes in many areas, especially in humid climates.
Mulch
Mulch with pine needles, straw, or compost to help keep moisture in the soil and prevent weeds. Mulch should be 2 to 3 inches deep for effective weed control. This photo shows the soaker hose just for demonstration purposes, but in your garden the hose will be completely covered with 2 to 3 inches of mulch.