Heirloom Rainbow Mix

Plant your heirloom tomatoes in full sun, or at least six hours of direct sunlight a day. Some experts recommend eight hours. There's one caveat: Many gardeners start heirloom tomatoes by seed indoors. 

If that's the case, harden off your seedlings by gradually increasing their time outdoors. Place your transplants in a sheltered spot in bright, indirect light, slowly adding an hour or two of outdoor time a day. Transplant your tomatoes once they are acclimated to full sun. Tomatoes are heavy feeders that benefit from fertilization. The best approach is to have your soil tested so you can receive recommendations specific to your garden. If you don't get your soil tested, you can choose a fertilizer formulated for tomatoes and other vegetables. These fertilizers typically have a lower nitrogen level, as too much nitrogen causes plants to produce lots of leafy, green growth instead of fruit. Commercial tomato fertilizers usually contain calcium as well, which helps prevent blossom-end rot.

Fertilize when first transplanting your tomatoes, mixing the fertilizer well into the soil according to the directions on the label. When the first fruits appear, side-dress the plants with more fertilizer (usually 2-3 Tbsp. per plant). Some gardeners continue fertilizing every four to six weeks during the growing season, but this is weather-dependent—don't fertilize your plants during a heat wave.