Nearly 15 years ago on the island of Crete, Alice Doyle discovered grafted tomatoes. She was there to meet a brand-new extended family when someone pointed out a field of plants where a nematode infestation had devastated crops in previous seasons. The grafted tomato varieties were impervious to the pests.
"I really didn't think about it as important for the home gardener," she said. But it stuck in her mind, and over the years she began to think about it more and more.
Ms. Doyle, who runs Log House Plants in Cottage Grove, Ore., wondered, "Why isn't the home gardener enjoying all the benefits that grafting brings?"
Here's how it works: A special seed is selected for vigor, disease resistance and/or other traits. It's called the root stock. It might be a wild species that wouldn't produce much of a tomato at all. Another tomato variety, called the scion, is selected for taste, size or other attributes. These are the varieties we're familiar with, such as 'Brandywine,' 'Jetsetter,' 'Cherokee Purple' and others. Any favorite tomato could act as the scion.
Seeds of the root stock and scion are planted. When the root stock is the right size, its top is cut off and the stem of the scion is attached to it with a grafting clip.
Under the right conditions, the two become one. There's no DNA exchanged. The scion benefits from the vigorous root stock that is resistant to soil-borne diseases and can be three times larger than a standard tomato's root system. Larger roots mean the plant can pull in more nutrients for the plant.
"You have these roots that are creating more mass, so they actually do more with less," Ms. Doyle says. These plants will use less water and fertilizer.
These tomatoes have other advantages, too. Even though they shut down like most tomatoes during extreme heat, the plants rebound quicker. When things cool off, the tomatoes last longer into the fall. When the plant is still covered with fruit as frost looms, Ms. Doyle recommends cutting it at the base and hanging the plant upside down in a warm place to let the fruit ripen.
Even though the rootstock can't prevent airborne diseases or fungal issues such as early blight, it can often fight them off more effectively because the plant is so prolific. Grafted tomatoes can also tolerate soils with higher salt levels.
In 2011, 1 billion vegetables were grafted around the world.
"Once a gardener plants a grafted plant, they will never go back," Ms. Doyle says.
Log House Plants, a wholesaler, became the first company to offer grafted tomatoes to gardeners in the U.S., originally offering them exclusively through Territorial Seeds. About the same time, John Bagnasco from GardenLife was also working with grafted tomatoes. The two companies teamed up with grower Tim Wada of Plug Connection to form SuperNaturals Grafted Vegetables LLC. They charge around $7 per plant.
SuperNaturals has also partnered with Aaron Whaley of A.P. Whaley Seed Co. to add interesting vegetable varieties like the Indigo series of tomatoes. The fruit sports various shades of purple and is high in antioxidants called anthocyanins.
Mr. Bagnasco, who also hosts the popular radio show "GardenLife," saw a need for grafted tomatoes in the home garden. "People just love the taste of heirloom tomatoes, but you can't grow heirlooms everywhere in the country because you've got disease issues in the soil and you've got nematodes. Our root stock is resistant to all soil diseases and nematodes. Now you can grow an heirloom anywhere."
'Brandywine' is one of the most popular heirlooms. Gardeners are lucky to pick half a dozen in a season he says, but trials of a grafted 'Brandywine' produced 50 to 60 tomatoes on each plant.
The trick to successfully growing a grafted vegetable is not to bury the graft point, Mr. Bagnasco says. Doing so negates the positive traits associated with grafted plants. It's an easy mistake to make, especially with tomatoes because many gardeners place their transplants deep in the soil. Even professional growers made the error the first year the plants were shipped.
The company also offers seeds of the root stock, and I wondered why they would sell them. "Because we know how hard it is," he said.
In his operation grafts are nearly 100 percent successful; a novice will be lucky with half that rate. "If you had one [tomato variety] you wanted to do, you could do it yourself. It's kind of a fun project," he said.
Because he works with tomatoes for a living, I had to ask what some of his favorite varieties were. He loves 'Blush Tiger.' "It might be the world's best-tasting tomato," he said with a smile. The other tomatoes he's thrilled about are the Bumblebee series. These striped cherry tomatoes in purple, pink and orange are tasty and beautiful.
SuperNaturals has branched out from tomatoes to eggplant, peppers, basil and vine crops. Although the cucumber plants don't produce more fruit, they are highly disease-resistant and very vigorous. It's the cantaloupe and watermelons that really pack on the fruit.
"You get a minimum of double amount of melons and sometimes three or four times the amount of melons," Mr. Bagnasco said.
In fact he offered some grafted 'Ali Baba' watermelons to Portland, Ore., master gardeners. At the end of the season the local paper was out to photograph vines loaded with 35 to 40 pound full-sized melons.
After a little prodding, he revealed some of the fascinating plants on the horizon for 2015. The first two are not grafted: a sweet corn plant with red foliage, husk, kernels and tassels that is 30 percent protein and a blue edible podded pea. 'Ketchup "N" Fries' is a cherry tomato scion grafted to potato root stock.
Grafted plants might be the future for tomatoes and other vegetables as they use less resources and produce more fruit than standard varieties. It's something gardeners will be experimenting with for seasons to come.