Heirloom tomatoes, representing family favorite varieties swamped by the agribusiness switch to hybrid tomatoes in the 1960s, have been making a comeback since the 1990s as a result of the sustainable agriculture movement. Still, few nurseries will have heirloom plants, so you'll need to grow your own heirloom tomatoes from seed starting four weeks before the last frost. Organic gardeners will find that heirloom varieties fit well with the traditional, chemical-free natural techniques of vegetable raising.
Purchase seeds at health-food stores, garden centers and via online specialty purveyors. Buy seeds of varieties known for resistance to foliage diseases, especially important in humid climates, including Eva Purple Ball, Cherokee Purple, Druzba, Red Brandywine and Zogola, recommends heirloom tomato specialist and author Carolyn J. Male.
Plant the seeds 1/4 inch deep in growing flats containing sterile growing mix on a heat mat. Water the seeds. Remove the heat mat when they germinate and place the sprouted plants 2 inches under a fluorescent light.
Prepare the soil in the sunniest part of your garden for the heirloom tomatoes. Mix compost in the soil before planting by placing a layer 1 or 2 inches deep on top of the soil and raking it in or by mixing compost into the planting hole.
Mulch the surface before planting to prevent or delay disease spores in the soil from splashing up and infecting young plants, recommends gardening author Annette Welsford. Most horticulturalists, and even the editors of Organic Gardening magazine, recommend red or black plastic mulch, but you can also use leaves or other organic materials.
Plant the heirlooms outdoors about a week after the last frost date. Space plants well apart, 2 feet or more, to fight the problem of foliage diseases before they start by providing air circulation between plants.
Slit Xs in the plastic mulch, make a hole with a trowel, and place the tomato's root ball and stem and lowest leaves in a hole, then backfill and firm the soil.
Cage the plants using concrete reinforcing wire bent into 3-foot rounds. Many heirlooms grow tall and wide and need the support of a strong homemade cage.
Place additional shovelfuls of compost around the tomatoes during the growing season, to provide "almost every nutrient tomatoes need," recommends Cornell University horticultural professor Stephen Reiners.
Water heirloom tomatoes deeply, using regular or soaker hoses once a week, or more often for heirlooms in containers, whenever the top inch of growing mix dries out.
Harvest fruits as soon as they start to turn color and allow them to finish ripening in your kitchen.