Black tomatoes, heirloom tomatoes originally from the area around the Crimean Peninsula, are not really black. The skin is often dark red, with mottled dark patches, and the interior ranges in color from maroon to purple. These tomatoes, along with other heirloom tomatoes, have been increasing in popularity because of their sweet flavor and unusual, striking markings.
Hybrid tomatoes, bred for uniformity and appearance, have lost many of the genetic resistances that heirlooms have developed to the many blights that plague tomato growers. For this reason, many gardeners are turning to heirloom tomatoes. Unlike hybrid tomatoes, which may be attractice yet flavorless, heirlooms are hearty and flavorful. Heirloom tomatoes are genetically robust and have been handed down through generations of gardeners who save the seeds.
Heirloom tomatoes, as a general rule, are not available in commercial nurseries, so gardeners need to start the plants from seeds. The seeds are available from many online sources. Start the seeds indoors about six to eight weeks before the frost free date for your area. Plan to set the plants in the garden two weeks after the last frost date.
Start with commercially prepared seed planting mix for best results. Moisten the planting mix thoroughly and put in peat pots or large trays with individual cells for each plant. If you are reusing containers, make sure to sterilize them first with a 5 percent bleach solution.
Pack the moist soil into each pot or cell and plant one seed in each, about 1/4 inch deep. Tamp the mix down lightly and water gently. Put your pots in a large plastic bag, leaving one end open for air circulation. Do not let the plants dry out as dry seeds won't germinate. Place your plants in a warm area (70 to 80 degrees is ideal). When seedlings appear, usually after a week or two, remove the plastic and set the seedlings in a sunny window or under grow lights. When plants develop their first true leaves, transplant them to larger pots if necessary.
About two weeks before you plan to plant the seedlings, move them outside for an hour or two each day, gradually increasing their exposure until they can tolerate being out all day and night. Now is the time to plant them in the garden. For best results, stagger your plantings by a few days to extend the harvest season. If possible, plant on a cloudy day to prevent plants from drying out.
Amend the soil with plenty of compost and pinch off the bottom leaves. Tomato plants should be planted so that only the top cluster of leaves is above the soil. Space plants about 2 to 3 feet apart and set stakes or cages around the plants for support as they grow. Water well.
Tomato plants require lots of water so keep the soil moist. Watering six to eight inches deep, twice a week, will provide enough water. Do not let the plants dry out. During the hottest parts of the summer, mulching with straw, grass clippings, or plastic will help keep the moisture in. Fertilize regularly using a commercial fertilizer made for tomatoes, following the instructions on the packaging. Commercial fertilizers are available in both organic and non-organic formulae.
Wait until your black tomatoes are fully ripe before harvesting. Wash and dry the fruit, then store on a kitchen counter until ready to eat or preserve.