Tomato Grafting: It's Easier Than You Think and Will Yield Results

Blight is more of a problem for gardeners than ever before, but grafting your plants will make them much stronger and disease-resistant.


With the days getting longer, it's officially time to start planning the garden. At the very least, make a cup of tea and open a seed catalog. Depending on what you have in mind, it might be time to place an order.

If your plans include tomatoes, especially heirlooms, it's worth considering ways to fortify them. Anyone who's lost tomatoes to blight knows the heartbreak of yanking whole plants still laden with fruit, and removing them from the scene.

This is a big reason why many small farmers and serious gardeners have picked up the art of tomato grafting in recent years. Done much the same way that fruit trees are grafted, it's a process that has helped growers achieve dramatic improvements in tomato yield and disease resistance -- especially soil-borne diseases like blight.

Disease is more of a problem now than ever before. The efficiencies of global travel have enhanced the ways that plant disease can spread. And fickle weather conditions can create opportunities for disease to break out in unexpected places.

Ask a New England tomato grower about the 2009 season, and expect a grimace for an answer. The late blight fungus hopped from field to field virtually overnight, taking hold thanks to unseasonably cool and wet conditions in June and July. Few tomatoes, heirloom or hybrid, organic or conventional, survived.

The pathogen that causes late blight, Phytophthora infestans, also caused the potato blight of the infamous Irish famine. Conditions favor late blight only sporadically in New England, and before 2009 many gardeners had never seen it. Home gardeners were apparently the primary incubators for the disease. The outbreak was blamed on infected tomato plants sold at garden stores.

The easiest way to avoid late blight (there's also a related early blight) is to choose from a ever-widening selection of hybrid seeds for blight-resistant plants. I grew Mountain Magic and Defiant last year, both of which are resistant to both early and late blights. We had a cool, wet summer and several gardeners and farmers I know lost their tomatoes. My resistant tomatoes did great, and Mountain Magic is tastier than most heirlooms. Dark, rich, and meaty, they grow in beautiful red clusters of smallish fruit. I'd grow Mountain Magic even if blight were eradicated.

Beyond blight, there are many other tomato maladies to which the fruits are sensitive, especially those tasty, fragile heirlooms. There are wilts, nematodes, rot and viruses, salty soil, good old fashioned cold, and, now that average summer temperatures are rising, heat. Grafting tasty tomatoes like heirlooms onto tough hybrid rootstock is an interesting way of dealing with these issues, and for growing stronger, more productive plants.

As with fruit tree grafts, the upper part of the graft, called a scion, is chosen based on favorable characteristics of the fruit they produce. The heirloom scion is spliced onto rootstock -- the stem and roots half -- of especially hearty, disease-resistant, vigorously-producing varieties.

In Montana, the typically dry summers don't favor blight, but Missoula farmer Josh Slotnick is nonetheless excited to graft tomatoes this year for the first time. "In the literature, it appears that grafted tomatoes are much more vigorous and productive," he told me. "Heating greenhouse space in the spring and fall is expensive. If we can get more tomatoes per square foot, it's worth doing. Plus it's cool," he added, "and I want to learn a new thing."

It is pretty cool, and actually quite simple. In a mesmerizing YouTube video produced by the University of Vermont Extension Service, Westminster farmer Mike Collins demonstrates several grafting techniques. He makes the moves look easy, using only a sharp blade and some plastic clips to execute the simple yet delicate steps.

In Vermont, the growing season is a sprint, and every second matters. Collins, who has been grafting tomatoes for 15 years, compares the various options in terms of growing days lost or gained.

Some companies sell seed bred specifically for rootstock: plants that, if grown out, would produce small, inedible fruit. These seeds tend to be expensive -- the Johnny's Selected Seeds catalog charges about $25 for a package of 50 seeds. Johnny's stocks four varieties of rootstock, including the Maxifort seeds that Collins uses.

Lynn Montgomery has been farming in New Mexico for 40 years. He told me he never used to worry about late blight, but in recent years it has become an issue he's had to adapt to. Montgomery grows tomato seedlings in Actinovate, a type of bacteria that can be applied as a fungicide to combat acute outbreaks of fungal disease. By drenching his potting soil with Actinovate, Montgomery is able to get the bacteria growing in the tomato plants, where they'll live throughout the tomato's life.

Meanwhile, Montgomery is preparing to graft himself to the grafting bandwagon. He ordered rootstock seeds, grafting clips, and seed for some of his scions from Johnny's, and more scion seed from Like Collins, Montgomery will use Maxifort for his rootstock seeds. Maxifort offers broad disease resistance and grows robust, deep roots, which enhances the uptake of nutrients and water, building strong, productive plants.

I was surprised to learn in the Sunrise tomato grafting forum (what, you didn't know there were tomato grafting forums?), that you don't need to order those expensive rootstock seeds. Many hybrid tomato plants are bred with all kinds of disease resistance, like those Mountain Magic tomatoes that so captured my heart. In fact, the Mountain lineage of tomatoes, including Mountain Magic, includes some of the most disease-resistant plants there are. They make great rootstock.

It's also possible to graft several different scions onto a single rootstock, so that a single plant can produce Brandywines, green zebra, yellow stripe, and purple Cherokee tomatoes. Such a strategy might be useful for limited-space situations, like container gardens, which are especially susceptible to disease.

If you're growing tomatoes in containers, or just lazy, or cramped for space, more nurseries are stocking grafted tomatoes. It's also possible to order them online. Now you have no excuse not to get your graft on.

Image: George Africa.