Tall tomato plants often seem to produce fewer tomatoes than their shorter counterparts, usually because tall tomato plants need a stronger root system to become healthy and strong. One strategy for planting tall tomato plants is to plant them at a slight angle and bury the lower part of the stem to help form a more extensive root system. Trench planting is one of the best ways to plant your tall tomato plants. With the right soil amendments and water, you can have healthy, fruitful tall tomato plants in your garden.
Select a planting site for your tall tomato plants that has well-draining soil with an ideal pH of 6.5 to 7.0 and full to partial sunlight. Wait until the soil is warmer than 50 degrees F in the springtime before planting.
Loosen the soil to a depth of at least 6 inches using a pitchfork or rototiller. Work the soil when it's slightly dry and not wet, sticky or clumping.
Spread a 2-inch layer of organic compost, aged manure or peat moss onto the soil bed, and mix it into the soil down about 6 inches. Also mix into the soil a 6-24-24 or 8-32-16 NPK (nitrogen-phosphorous-potassium) granular fertilizer.
Place your tall tomato plants still in their pots on the planting bed to help them acclimate to the environment before planting. Allow the tall tomato plants to sit out at the planting site for one or two days and water them each day to keep them moist.
Dig a small trench for each tall tomato plant that descends into the ground at a 30-degree angle. Make the lower end of the trench as deep as the height of the tomato plant's root ball and lower stem, leaving only about 5 inches of the plant's top above the ground.
Trim all the leaves from the lower part of the stem that will be planted underground using sharp scissors or garden shears. Set the tall tomato plant root-first down into the lower end of the trench and back fill around the plant with the displaced soil.
Plant any additional tall tomato plants in the same fashion, spacing the plants 3 feet apart in rows that are 4 to 5 feet apart.
Water the soil around the tall tomato plants thoroughly to soak the soil down to the root balls. Apply a liquid 10-52-17 or 15-30-15 NPK fertilizer to the plants during the watering, at a rate of 2 tbsp. per gallon of water.
Stake your tall tomato plants by inserting a wooden stake beside each plant and tying the plant's stem to the stake with string or soft twine. Allow at least ½-inch of slack in the string or twine to allow for stem growth. Or place tomato cages around your plants instead of staking them.