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Graft tomatoes, especially heirlooms, for greater yield and disease resistance

publication date: May 26, 2008
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author/source: George DeVault
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By George DeVault

Growers of heirloom tomatoes now have a new best friend.  It is not some fancy fungicide, a super fertilizer or even a rare variety recently rescued from extinction.  It is a tool that has excited and empowered hobbyists and artists for more than 70 years -- the lowly X-acto precision knife.
    With one angular slice from this scalpel-like blade, heirloom tomato growers can reap the best of both worlds, the incomparable taste of tomatoes that really taste like the tomatoes our grandparents ate, plus the increased vigor and considerable disease-resistance of modern hybrid tomato varieties.
    The secret is simple:  Graft your favorite tomato variety, heirloom or otherwise, onto a disease-resistant rootstock.
    “I will not grow an heirloom tomato that is not grafted anymore,” declares 33-year-old Brandon Fahrmeier.  With his 24-year-old brother, Bret, Fahrmeier grows about 30 different heirloom varieties in Lexington, Mo., about 40 miles east of Kansas City.  They raise 76 acres of produce.
    “Grafting is 10 times better than we ever thought it would be. Typically, on an heirloom we were lucky to get six weeks of picking. Now we get 12 and even 20 weeks, and we only sprayed twice,” adds Brandon Fahrmeier.  The brothers have grafted 2,000 heirloom tomatoes for planting this season.
    Their heirlooms retail for up to $4.99 a pound at two farmers’ markets and an upscale supermarket in Kansas City.  “The grocery store buyer first said he would take 300 cases a week.  We were delivering 3,000 cases a week, and he took ‘em all and he kept calling for more.  His tomato sales were up 80 percent.
    “The buyer said, ‘I have never seen California-quality tomatoes coming out of Missouri or the Midwest,’” adds Fahrmeier.  “We’re picking #1 quality heirloom tomatoes, which if you know anything about heirloom tomatoes, you know they’re not typically a #1 tomato, anyway.  We are able to get #1s and a lot of #2s.  If it’s blemished, it’s graded #2.  We have strict quality control.”
    Self-described “minimalists,” the Fahrmeier brothers experimented with grafting in hopes of cutting back even more on spraying.  Vermont grower Jack Manix, on the other hand, became a grafter out of self-defense against serious disease problems in long-used greenhouse soils.  Instead of heirloom tomatoes, though, he routinely grafts a commercial hybrid greenhouse variety that lets him start picking tomatoes by about the middle of May.  Manix has 19 greenhouses, half of which are certified organic.
    “Just about everybody I know, after five or six years, they start having soil problems,” explains Manix.  Some of his soils have been in continuous production for about 16 years.
    “We were having some problems with the soil.  We tried Rootshield and other bio-pesticides. They helped a little bit, but they didn’t really stop the pathogens.  The tomato variety we use (Buffalo) is more susceptible than probably most commercial tomatoes.  We started grafting onto cherry tomato stock, because they seem to grow anywhere.”  
    Traditional and more costly solutions to greenhouse disease problems include steam-sterilizing or fumigating the soil with methyl bromide, scooping out the old soil and replacing it with new soil or building a new greenhouse on virgin soil.
    “Instead of investing in another structure, grafting allowed us to get our plants to produce more,” says Manix.  He grafts about 2,000 tomato plants a year, including custom-grafted plants for other area growers who don’t want to start their greenhouses as early as he does.  His customer list includes a “very conservative,” non-organic grower who didn’t want anything to do with grafted tomatoes, at first.  The grower ordered 500 early tomatoes from Manix.  “When I gave him the plants, I threw in a tray of 15 grafted plants.  Next year, he said, ‘I want ALL grafted plants.’  The difference was that noticeable.”
    Scientists agree. “Researchers around the world have demonstrated that grafting can be effective against a variety of soil-borne fungal, bacterial, viral, and nematode diseases,” reports North Carolina State University Extension in a bulletin titled “Grafting for Disease Resistance in Heirloom Tomatoes.”  (The 8-page bulletin is available free on-line at www.oardc.ohio-state.edu/graftingtomato/.  Click on the “Grafting Methods” button.  That web address is home to Ohio State University’s web site “Grafting Tomatoes for Organic and Sustainable Production.”)
    The bulletin points out that:  “Grafting can be used to unite soil borne disease-resistance and enhanced vigor of hybrid tomato cultivars with the high fruit quality of heirloom varieties.  It has been used to eliminate verticillium and fusarium wilt in tomato and cucurbit production systems in Japan, Korea, and Greece.  In New Zealand, it has been used to reduce levels of corky root rot.  In Morocco and Greece, grafting is used to control root-knot nematodes in both tomatoes and cucurbits.  Researchers have proposed using grafted plants instead of methyl bromide to manage soil borne diseases in these regions of the world.
    “In India, wilt-resistant rootstocks were used in one experiment to reduce bacterial wilt in tomatoes.  By the end of the season, none of the control plants had survived, while 100 percent of the grafted plants continued to produce.  Furthermore, the yield of the tomatoes with resistant rootstock was four times that of non-grafted, susceptible plants.”
    Johnny’s Selected Seeds has also produced a bulletin on the subject:  “What You Should Know about Grafting Tomatoes To Control Fusarium Wilt & Other Diseases.”  It is available free in pdf format on Johnny’s web site (www.johnnyseeds.com/Assets/products/110847191121410.pdf).  “Grafting can improve production and overall crop health and vigor, reduce plant mortality rate resulting from disease, reduce or eliminate the need for pesticide use, lengthen harvest duration, and significantly increase net income,” the bulletin observes.
    “After an initial ‘learning-by-doing’ period, you should be able to complete 75 to 100 grafts per hour.  Experienced grafters should be able to perform between 1,500 and 2,000 grafts a day.”

Grafting in context
    Grafting has been known and practiced for many thousands of years, primarily by master growers of apples, grapes and other fruit.  Grafting was practiced and elevated to a high art by the ancient Chinese, Greeks and Romans, among others.  But grafting of vegetables, primarily to reduce fusarium wilt on watermelons in Asia, didn’t really catch on until about the 1920s.
    “In Japan, almost 95 percent of the watermelons, oriental melons, cucumbers, tomato and eggplant crops are grafted before being transplanted to the field or greenhouse,” reports Ohio State University.  “Grafting may be an important component of low-input sustainable and organic horticulture due to increase in vigor and disease resistance.”
    “The ways or fashions of grafting are legion.  There are as many ways as there are ways of whittling,” Liberty Hyde Bailey wrote in 1928 in the “Standard Cyclopedia of Horticulture.”   “The operator may fashion the union of the stock and the scion to suit himself, if only he apply cambium to cambium, make a close joint, and properly protect the work.”
    Fahrmeier and Manix are examples of exactly what Bailey was talking about.  Each grower uses a different grafting method -- Fahrmeier the “top,” “tube” or “Japanese tube” graft, and Manix the “side” or “cleft” graft -- and each gets excellent results.  (See sidebars for step-by-step details and diagrams of both methods.)
    Once again, science proves the growers right.  “On the basis of the high percentage of successful grafting observed for ... using cleft and tube grafting methods, it can be concluded that both methods are suitable for tomato grafting,” researchers at the University of Ljubljana in Slovenia reported in 2004.  “Since grafting gives increased disease tolerance and vigour to crops, it should be useful for low-input, sustainable horticulture of the future.”
    Fahrmeier raises many of his tomatoes in a 2-acre Haygrove tunnel (www.haygrove.co.uk), instead of more traditional high tunnels or greenhouses.  His only regret is that he didn’t build a bigger tunnel, sooner.
    “They survived 16 degrees outside and 34 degrees inside on the plastic.  We lost 50 plants out of 3,000 plants.  They were near the end walls where we had air leaks,” he says.  Kerosene heaters did little to warm such a large area.  Solar warmth trapped by the tunnel, itself, and row covers saved the crop.  Midsummer temperatures stayed in the hundreds for several weeks.  That caused tomato blooms to abort, inside and out.  But light-diffusing Luminance poly kept the tunnel temperature about five degrees cooler than outside.
    Fahrmeier’s success rate with grafting was about 40 percent, at first.  Now it is 95 percent.  He grafts about 100 plants per hour.  Bigger plants do better, he says.  They should be half the thickness of a pencil.  Fahrmeier and Manix both graft onto Maxifort rootstock, which costs $54.50 for 250 seeds from Johnny’s.  Other Maxifort quantities and prices are 500 seeds, $99.50; 1,000 seeds, $186; 5,000 seeds, $173 per thousand.
    Is the extra cost of the rootstock worth it?
    “Absolutely!” says Fahrmeier.
    “That is a superb, vigorous rootstock,” says Manix.  “Considering the cost of structures and heat, getting 40 percent to 50 percent more production will help defray some of the rising costs.”

Don’t be afraid
    What advice do these veteran grafters have for people just thinking about trying it?
    “Just do it,” says Fahrmeier.  “Don’t be scared.  It’s not that big a deal.  Try a few plants maybe two weeks before you want your tomato plants.  Start 10 seeds of each (scion and rootstock).  Experiment a little with those 10 plants.  Do your homework first, but don’t be scared.  It seems like a complicated process, but it’s rather straightforward and simple.
    “When you’re planting, be a little bit careful to make sure the rootstock is not planted too deep.  If the top is touching the soil or under stress, it will root into the soil and that defeats the whole purpose.  It takes a little more care to plant them.  Even then, sometimes a plant will snap at the graft if you’re a little rough when planting.”
    “Even if soil disease is not presently a problem, grafted plants can allow growers to harvest a larger crop without significant investment in more structures,” says Manix.  “There is also an economic opportunity to provide custom-grafted plants for other growers.”
    “It looks more complicated that it is.  It’s like grafting apple trees.  There is a little bit of a learning curve, but it’s basically simple and your time is well spent, economically.”

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George DeVault is a farmer, writer and executive director of Seed Savers Exchange. 


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