Heirloom tomatoes are varieties older than 50 years that are still in production due to their highly desirable characteristics. Many heirloom varieties maintained longevity due to families saving and passing the seeds through generations. The seeds are now commercially produced and available for purchase as seedling plants or packets of seeds. Heirloom tomatoes differ from hybrid varieties with longer seed-to-harvest dates and lanky, branched plants that produce large clusters of fruit.
Prepare the planting area for heirloom tomatoes by working the soil to a depth of 10 inches with a tiller. Rake the area to remove weeds and other vegetative growth from the soil.
Test the soil pH, as heirloom tomatoes grow best in a pH of 5.5 to 7.0. Add ground rock sulfur to the soil and work it to a depth of 6 inches to lower the pH value or work limestone into the soil raise the pH value. Water the garden area well and let it rest for two weeks before planting heirloom tomato seedlings.
Sprinkle a tomato starter fertilizer across the prepared soil at planting time. Dig planting holes for the heirloom tomatoes that are 2 to 3 inches deeper than the seedling root ball and spaced 15 inches apart.
Set the tomato seedling into the planting hole so the bottom set of leaves are approximately 1 inch above the soil level. Fill the hole with soil and gently tamp to hold in place. Water the heirloom tomato plants at the soil level immediately after planting to stimulate root establishment.
Provide 1 to 2 inches of water each week during the growing season to keep the soil most. Do not allow the soil to dry, as this will reduce plant health and fruit production. Place dry grass mulch around the heirloom tomato plants to prevent weed growth, which competes for moisture and decreases air circulation.
Fertilize heirloom tomato plants with a low-nitrogen tomato fertilizer twice a month, once the blossoms form. Use a water-soluble fertilizer and apply it to the soil around the plants without making stem contact.
Remove non-flowering branches and leaves that touch the ground once the heirloom plant begins to grow. Leaves touching the soil may contract a fungal disease.
Provide support by placing a cage around the plants shortly after planting. Train the branches through the cage as the plant grows. Many heirloom varieties produce long branches that break easily when filled with fruit.