Grafting a better tomato plant

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As cabin fever reaches its pinnacle, seed catalogs provide cool relief for gardeners hoping for a great tomato season. But the great late blight tomato plague of 2009 still weighs heavily on many gardeners' minds. Are grafted tomatoes the answer?

The first page of the Territorial Seed catalog offers grafted tomato plants, something home gardeners have rarely if ever seen before. Grafting -- the process of attaching a vigorous, disease-resistant rootstock to a favorite variety -- is popular in Europe and Asia, and it has been done for decades by commercial tomato growers in the United States.

Josh Kirschenbaum, product development coordinator for Territorial Seeds in Cottage Grove, Ore., worked closely with a nearby wholesale grower, Log House Plants. After successful field trials last season, he decided it was time to offer the plants to customers this year.

"The main advantage of a grafted tomato is disease resistance as well as vigor and a longer harvesting period," he said.

While the rootstock contributes disease resistance and vigor, the scion is chosen for fruit quality, size, flavor and everything else a home gardener would want. Interestingly, the rootstock is bred from a wild tomato, and if grown alone, it might not even produce fruit.

PG VIDEO: How to graft tomatoes

Territorial is offering grafted versions of 'Brandywine,' 'San Marzano Gigante,' 'Japanese Black Trifele' and 'Big Beef.' "All of those are great tomatoes," Mr. Kirschenbaum said, but they're not necessarily the most productive or the most disease-resistant.

Another option is two different varieties grafted onto the same rootstock -- 'Sungold' and 'Sweet Million,' for instance. Other combinations include 'Brandywine' and 'Super Marzano,' 'Golden San Marzano' and 'Viva Italia,' and 'Legend' and 'Koralik.' The latter are both determinate (non-vining), and 'Legend' is said to be late blight-resistant.

Mr. Kirschenbaum doesn't recommend these plants for containers due the vigorous nature of the root stock. He thinks they are perfect choices for gardeners who don't want to use chemicals.

In the trials, he saw grafted plants producing much more fruit with fewer diseases. But one of the most impressive things was that plants were healthy and productive until the end of the season. The un-grafted plants were tiring and succumbing to fungal diseases by the fall.


Single varieties are $6.95, doubles are $11.50 and both are shipped in 21/2-inch pots. The plants are approximately 6 to 8 inches tall and are shipped from April until the end of May.

Mr. Kirschenbaum teased with the news that other types of grafted plants might become available in the next season or two, including peppers, eggplants, watermelons and cucumbers.

Grafted tomatoes are nothing new to 71-year-old Frank Sporie of Latrobe, who combined a tomato and a potato plant as a high school freshman in the 1950s after seeing a story in Life magazine. Inspired by his mother, who once put up 800 cans of tomatoes, he's gardened since World War II. He still has a snapshot of himself as a child holding a muskmelon.

"I've had dirt under my nails ever since,' he said with a laugh.

The former horticulture teacher is on a mission to make grafting rootstock available to home gardeners at a reasonable price. He doesn't like the fact that most rootstock seed is hybrid, meaning that gardeners must buy rootstock seed each season from seed companies.

Hybrid seed can't be saved from year to year because it does not grow true the next season, reverting to one of the parents used to create the variety. Seeds from open-pollinated types like heirlooms can be saved to produce the same variety of tomato year after year.

By trying to come up with a variety that will work well as an open-pollinated rootstock, he's hopes to help gardeners save their own seed to use annually. He's also looking at cheaper hybrids.

Mr. Sporie has 11 varieties of rootstock seed, and he's going to be trialing them this summer with a variety of scions. Eight of the rootstock varieties are hybrids, and three are open pollinated. He selected the varieties for their disease resistance.

He says with a few simple tools, gardeners can start their own seeds of rootstock plants and do their own grafting at home.

"Anybody that can slice a banana and put it back together so it didn't appear to be cut can graft," he said.

Most importantly the grafting area, tools and hands should be clean to reduce chance of diseases. He'll start seeds for the scion 10 days before the rootstock. Mr. Sporie leaves the bottom leaves on his rootstock plant. Then with a razor blade, he makes a 45-degree cut on the stem above the first true branch. He looks for the same size diameter stem on the scion and makes a cut there. Think of the stems as pipelines with different layers; they must match up for the best results. The scion is butted to the rootstock and held in place with a silicon grafting clip or rubber tubing.

The plants need high humidity, so they can either be misted or covered in plastic like cuttings. They are kept shaded the first couple of days, then slowly acclimated to light. In about five days, the graft will have taken.

When it's time to plant, the graft union must be well above the soil level. If not, it would produce the rootstock tomato, which would probably be inedible.

One other note in Mr. Sporie's system: The branches left on the rootstock below the graft should not be allowed to flower. Those flowers could possibly cross pollinate with the scion or other tomatoes and produce a different variety. The results of Mr. Sporie's trials will be reported here at the end of the season.

Just like anything gardening, there are many different methods of grafting; there are lots of videos and information on the Internet. Johnny's Selected Seeds offers some of the most popular rootstock varieties, including 'Maxifort,' 'Emperador' and 'Beaufort.' All are F1 hybrid seeds, and prices start at $16.90 for 50 seeds. The company also carries other grafting supplies.

Mr. Sporie has one goal for his project:

"All I want to do is help the home gardener have some fun," he said.

Doug Oster: or 412-779-5861.


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