Grafting: A new way to grow tomatoes

Are you one of those people who has a hard time finding a new sunny place in the yard to plant your tomatoes every year? Or perhaps a lover of heirlooms who annually watches them fall to disease prematurely in the season? Well, there may be an answer for you in grafted tomatoes.

Grafting involves joining the rootstock of a hardy and reliable tomato variety to an heirloom or other variety that does not have such hardiness. The rootstock conveys its strength into the soil while the top of the plant, the scion, goes about its business of producing flavorful tomatoes.

You can see grafted tomatoes growing alongside their non-grafted counterparts today during Tomato Day at the Extension Center, 21st and Ridge Road. Cary Rivard of K-State will give a talk about grafting tomatoes at 11 a.m. as part of the annual tomato celebration.

Grafted tomatoes became more available to the public this year through some mail-order catalogs, and some people, including the Sedgwick County master gardeners, have grafted their own. One thing about grafting is that the plants and seeds are much more expensive than the non-grafted, but for some diehard tomato lovers, it may be worth it.

There even will be an opportunity for people to learn grafting at a vegetable growers conference in Wichita next February, led by Rivard and extension agent Rebecca McMahon.

Rivard started doing research on grafting six or seven years ago and says he's been fielding calls from all over the country about grafted tomatoes this year.

"When we first started doing research you could hardly get a rootstock," he said.

Now "we have half a dozen trials all over the state, and so far so good. They seem to be doing very well."

The grafted tomatoes have more disease resistance, including to pathogens in the soil, and most of the research is showing that they're also quite a bit more vigorous than their non-grafted counterparts, Rivard said, with a greater yield and longer season.

"One of the things people have seen is the root system is quite a bit larger."

And in this hot summer, more good news: Some rootstocks are more tolerant of high soil temperatures, Rivard said.

The heirloom that the testers are growing a lot is Cherokee Purple.

"That's a great-flavored tomato, but it's also just a weak plant. We found that it really likes to be grafted."

In addition to heirlooms, some determinate red slicers, most commonly VHN 589, are being used as the scions. Rivard said common rootstocks that are being used are Maxifort and Trooper.

Rivard said grafting is not difficult to do, but the timing is tied to a narrow window, when the plants are only 2 1/2 inches tall and only stay that way for 12 hours.

So far at the demonstration garden, there hasn't been much difference between the grafted and non-grafted tomatoes. But the grafted Black Krim is starting to look a little better than its non-grafted counterpart, McMahon said this week.

"We planted them in a bed we know has nematodes in it, so we expect the grafted plants to stay healthier longer, and we're hoping to see that the grafted plants would be more vigorous and productive than the non-grafted plants. But so far they're not super-productive because the weather's been obnoxious."

(But in another test being done in the demonstration garden, McMahon said, "the 'hot-set' tomato varieties that were planted in mid-June are starting to bloom, so this is a great test to see if they are going to set some tomatoes in the heat. We'll be keeping an eye on them for the next couple of weeks, looking for some tiny green tomatoes.")

The grafting will help prevent other diseases such as fusarium wilt that can build up in the soil if you plant non-resistant plants several years in a row in the same place, McMahon said. Generally, tomatoes and the other vegetables in their family should not be planted in the same spot for three years because of the disease build-up.

Alice Doyle, owner of Log House Plants in Cottage Grove, Ore., which sells grafted tomatoes on its website, loghouseplants.com, says she finds her rootstocks in Holland and buys grafting clips in Japan. The newly grafted tomatoes sit in a dark and humid room for three days to reconnect the vascular tissues. Then they go through a weaning period before they are moved to the greenhouse.

For the home gardener, planting a grafted tomato is a bit different. In this case, you do not want to plant your tomatoes deep. Instead, you want to be sure the graft is clearly above the ground so only the rootstock roots in the garden.

Grafted tomatoes need support as the graft can be a weak spot that can break if the plant flops over. These tomatoes have to be caged and tied right away.

"We've been playing around with grafting two kinds of tomatoes on one plant," Doyle said. "For gardeners who don't have a lot of space, one plant in a pot makes a colorful salad."

Doyle has been combining Red and Yellow Brandywines and Black Cherry and Snow Wild Cherry tomatoes on one plant.

This story was originally published July 23, 2011 at 12:00 AM with the headline "Grafting: A new way to grow tomatoes."