My hybrid tomatoes usually grow well enough, but every time I try to grow an heirloom variety, the plants turn yellow and die. My neighbor says they fail because of diseases in the soil. What can I do to prevent these problems? I would love to be able to grow ‘Brandywine’ at least once!
Tomatoes that grow well for a while and then show noticeable yellow color as they wilt are usually infected with one or more strains of fusarium fungi, a common and persistent problem in soils in warm climates. Other soilborne pathogens, such as verticillium wilt or root knot nematodes, may also be involved.
Whatever the specific problems, your hybrid tomatoes probably grow well because they provide genetic resistance, while most heirloom varieties are susceptible. There are two solutions: Grow heirlooms in containers filled with bagged potting soil, or graft tomatoes to combine the flavor of heirloom varieties with the disease-resistance of hybrids.
Containers are an easy solution if you are working with purchased seedlings, but if you start your own seeds, you may be surprised at how simple it is to graft tomato seedlings when they are about 6 inches tall. With a successful tomato graft, you get the disease resistance and vigor of a hybrid root system, but with fruit characteristics of great-tasting heirlooms. Even first-timers can expect at least half of their first tomato grafts to succeed. With practice, you will seldom lose a plant.
Your rootstock can be any hybrid that provides good resistance to the disease problems at hand. In your case, I would choose a variety with VFFN after the variety name for rootstock. This means the variety is resistant to verticillium, two races of fusarium, and rootknot nematodes. Exemplary varieties include ‘Bella Rosa’ VFFNA, ‘First Prize’ VFFNT, and ‘Goliath’ VFFNT.
To prepare to graft tomatoes, start seeds of your chosen rootstock and heirloom varieties on the same day, and give the seedlings plenty of light and excellent care for about three weeks. Meanwhile, study various grafting techniques, which are surprisingly simple to do. Online, be sure to review North Carolina State University’s overview of tomato grafting, and watch the video on grafting greenhouse tomatoes that was produced by the University of Vermont.
You don’t need to invest in special equipment to graft tomatoes for a home garden. Child-size, spring-type hair clips do a good job of holding cleft grafts together, and top grafts can be stabilized with a short piece of drinking straw slit down the side. The critical details are to graft tomato plants of exactly the same age and size, and to shield them from light for up to five days after the grafting operation is done. After the grafted tomato plants are hardened off and show vigorous new growth, it is important to set them high, so that the graft union is above the soil line.
Heirloom varieties of tomato grafted onto disease-resistant rootstocks will resist soilborne diseases, but they will still be at risk for early blight, late blight, and other foliar diseases that travel in wind and rain. Still, tomato grafting makes heirloom tomatoes as easy to grow as hybrids in gardens where common soil diseases are permanent residents.
Above: Consider grafting your favorite tomato varieties, such as this 'Brandywine' tomato, onto disease-resistant rootstock. Photos by William D. Adams (top) and Rick Wetherbee (bottom).
Contributing editor Barbara Pleasant gardens in southwest Virginia, where she grows vegetables, herbs, fruits, flowers and a few lucky chickens. Contact Barbara by visiting her website or finding her on Google+.