Grafted tomatoes grab attention with improved vigor, production and disease resistance

Published: Thursday, April 21, 2011, 8:20 AM

Mighty 'Matos soar onto the market this spring with, as the name suggests, the muscles of a superhero. Here come grafted tomatoes to save the day, or at least the wimpy crops of our favorite -- and most frustrating -- vegetable.

Unveiled last year in limited release by Log House Plants in Cottage Grove, the first crop of grafted tomatoes took off like a caped crusader. Portland Nursery, one of only four garden centers in the country to carry them, sold out quickly. As soon as people hear about the altogether-different tomatoes, they line up at the checkout counter. Who doesn't want the promise of a plant that produces more fruit for a longer season on a disease- and pest-resistant, vigorous plant that needs less water and fertilizer and adapts to poor soils?

After several years of experimentation, Log House succeeded in attaching varieties, such as 'Big Beef,' 'Brandywine' and ' 'Sun Gold' -- which are great-tasting but have disappointing results -- to the roots of ultra-strong plants that bear inedible fruit. This best-of-both-worlds process is similar to the grafting methods used for grapes, fruit trees and roses. (No genetic modification is involved in the process.) Though not available for home gardeners in the U.S. until now, grafted vegetables are widely grown commercially in Japan, New Zealand, Australia and throughout Europe, and are catching on with farmers in Canada and on the East Coast.

The method is exacting and time-consuming, says Alice Doyle, co-owner with Greg Lee of Log House Plants. But she was determined to figure it out after seeing her first grafted tomatoes in Greece in 2001. And, with help from her staff, she did, not only with tomatoes, but also peppers and eggplant. Last year, the wholesale nursery tested 70 tomato varieties. Grafted and nongrafted plants grew side by side in exactly the same conditions. The results were dramatic: much larger, healthier plants with pounds and pounds more fruit. After checking out the trials, Territorial Seed Co., also in Cottage Grove, quickly agreed to sell them. For the first time, the Northwest-centered company devoted the whole second page of its catalog to one type of plant. In its own tests, Territorial had an equally exceptional outcome. Even though the grafted tomatoes went in three to four weeks after the regular ones, they bore fruit much longer.

"There was a pretty considerable difference," says Josh Kirschenbaum, who does product development and public relations for Territorial. "At the end of the season, the majority of the non-grafted tomatoes had fizzled out; they got disease, fruit got mushy or they just quit producing. The grafted ones were still doing great. When the rain started, when diseases came on, they showed no sign of slowing down."

At the same time Doyle was embroiled in her experiments, John Bagnasco, one of the hosts of the national radio show "GardenLife" in Southern California, was doing his own research. He and Doyle met at a symposium in 2010 and decided to partner up. They created the business SuperNaturals Grafted Vegetables, and joined forces with Plug Connection, which will produce a million plants next year.

High-priced seeds, some up to 50 cents apiece, as well as exacting, time-consuming labor, drive the price up to about twice that of regular tomatoes, but that's not stopping gardeners from pulling out their wallets. The first of this year's crop that debuted at the San Francisco Flower & Garden Show in late March sold out, even though it was driving wind and rain outside.

"The response was overwhelming," says Bagnasco. "Every single person who had not heard of them wanted to try them."

BENEFITS OF GRAFTED TOMATOES

• Dramatically more fruit
• Produce earlier and longer
• Resistant to diseases, including verticillium wilt, fusarium wilt, root-knot nematodes and tomato mosaic virus. Because grafting produces vigorous, healthier plants, it likely will help ward off three of the other big tomato problems we face in the Pacific Northwest: early blight, late blight and blossom-end rot.
• Need less fertilizer and water
• Grow in poor soil
• Tolerant of swings in temperature

SOURCES
Garden centers throughout the Northwest supplied by Log House Plants. Store locator on website.

Territorial Seed Co., 2 1/2-inch plants for $6.95

GardenLife, 4-inch plants for $11.95

TIPS FOR GROWING GRAFTED TOMATOES

• Traditional tomatoes can be planted deeply because roots sprout all along the stem. With grafted tomatoes, it's important not to bury the graft because it will produce roots from the original plant (scion) without the benefits of the grafted rootstock. Plant at the same level as the top of the soil in the pot.
• Remove any suckers that come up from the roots, and any roots that form above the graft.
• Be vigilant about staking, trellising or caging so that the original plant doesn't root, and because the plant is more vigorous.
• Get even more fruit by pinching the plant so that you get two main stems.
• Prune some of the side branches and foliage of indeterminate tomatoes (those that keep bearing throughout the season) so that energy goes into producing fruit. No pruning necessary for determinate varieties.
• Keep 2 feet between tomato cages so that plants get plenty of air circulation and light from all sides.
• If you grow in a container, use a big one; a whiskey barrel is about the right size.
• Fertilize and water as you would regular tomatoes.

VARIETIES AVAILABLE
Log House grows about 20 varieties of single-grafted tomatoes. Plants grafted with two varieties are in limited release.

Single-grafted heirlooms
'Black Krim'
'Black Sea Man'
'Brandywine Red' and 'Brandywine Yellow'
'Cherokee Chocolate'
'Cherokee Purple'
'Gold Medal'
'Green Zebra'
'Japanese Black Trifele'
'Jaune Flamme'
'Matina'
'Moonglow'
'Rose'
'San Francisco Fog'
'San Marzano Gigante'

Single-grafted hybrids
'Big Beef'
'Cupid'
'Health Kick'
'Legend'
'Sun Gold'
'Sweet Million'

photo courtesy of Anthony Boutard

For all you science nerds out there, this is a cross section of the stem of a tomato scion, which must match up with the stem of the rootstock, taken with a special camera by Anthony Boutard of Ayers Creek Farm.

photo courtesy of Anthony Boutard

A cross section of the stem of a grafted tomato plant showing where the scion and rootstock match up.

-- Kym Pokorny