Dec. 29. 2011 - As the manager of three farmers markets in Central Texas, Greg Coley has noticed a few things about customer preferences. One of the first things he noticed is that there are a certain number of customers who don't show up before the farmers' tomatoes are ripe, and they don't return once the tomatoes are gone.
"For them, the market is over as soon as the tomatoes are gone," Coley said. "That's why you see a lot of growers figuring out ways to grow them in the year-round in greenhouses or whatever. People will buy tomatoes as long you have them."
If tomatoes are the star of farmers markers, the heirloom tomatoes are the superstars, having burst on the scene in the last few years like the newest sensation but, like a lot of superstars, heirloom tomatoes, and their more mainstream tomatoes, can be a finicky lot. In addition to greenhouses and "high tunnel "environments, there is some interest in grafting tomatoes to increase their chances for survival. The practice, especially in Texas, is new and untested, but research from other parts of the country has been promising.
Former Texas AgriLife Extension horticulturist Daniel Adams in his 2011-book "The Texas Tomato Lover's Handbook" notes that grafting has worked well in some experiments, especially with heirloom tomatoes.
"A vigorous, healthy rootstock with resistance to nematodes and other root problems can give a 'leg up' to heirloom or otherwise puny, disease-challenged varieties and make them more productive," Adams writes. "In theory, Texas gardeners might be able to grow Brandywine tomatoes, which prefer a New England summer, by using a rootstock with better pest resistance and increased vigor. Greenhouse tomato growers have been using grafted tomatoes for a while, and field production looks more promising."
Jamey Gage, with B-5 Farms in Kyle, is known for his heirloom vegetables, including tomatoes. He grafted a few tomato plants and said the results were intriguing but mixed, including some smaller fruit in the early season, and he plans to try it again soon.
"I didn't notice any major differences in the plants," he said. "There's a lot more interest in it now, and some of the research that's been done is pretty interesting. I think it's something to look into."
Researchers who have looked into it found that grafting provided different advantages for growers in different parts of the country, especially those using high tunnel or greenhouses. In other countries, grafting, which fuses a scion, or young shoot, onto a resistant rootstock, can protect against a variety of soil-borne fungal, bacterial, viral and nematode diseases.
In North Carolina, a study funded by the Sustainable Agriculture Research and Education (SARE) center used resistant rootstock to combat bacterial wilt in tomatoes. Ninety percent of the control plants died, but every one of the grafted tomato plants survived. A fact sheet on the study that is available at the SARE website.
According to the SARE study: "With little opportunity for extended crop rotation intervals in a high tunnel, disease pressure can be very high. Heirloom varieties are not bred for resistance, and, in organic systems, other disease management practices are limited. Due to the phase-out of methyl bromide in the United States, grafting could become a widespread pest management strategy for a large segment of growers."
Gage said that in his experience and what he has found from his own research is that the grafted plants will provide some disease resistance, but the plants can still be susceptible to certain soil-borne pathogens. "If the roots form along the stems, they will introduce some pathogens from the ground," he said.
Good root stocks are expensive and the process takes a little practice and a lot of preparation. After determining which scion and rootstock cultivars to graft, the plants are put in a healing chamber where humidity, light and temperature can be regulated. Construction of the chamber can be relatively simple, but placing it on the farm can be a problem. The grafts have to have between 80 to 95 percent humidity, no direct sunlight and a temperature between 70 and 80 degrees. The best place for the chamber is indoors where fluorescent lights can be used during the healing process and the temperature can be regulated.
Either two-piece plastic or silicone clips are used in the grafting process. Gage said the silicone clips were easier for him to use. He said the process can be a little intimidating at first but is not real hard once you get the hang of it. "You have to plan the time frame perfectly," Gage said. "It takes a little experience to get it right."
