GRAFTING TOMATOES // the local food report

From the top, it looks like an ordinary tomato plant. But this is not your average Mountain Magic. The fruiting scion has been grafted onto disease resistant rootstock to make a super plant—a tomato resistant to soil borne diseases and late blight, but with glossy, round sweet fruit.

The plant belongs to our friend Joe Leghorn, lawyer by week, gardener by weekend. He's always trying out new things in his Orleans plot, and this year's project is perfect tomatoes. He read about grafting in the New York Times and The Atlantic—the practice is relatively new in the U.S., but has been taking off around the world since about 2011. The idea is the same as with grapes and apples—graft a plant with tasty fruit onto a hardy rootstock, and you get the best of both worlds. 

Joe ordered his rootstock seed from Johnny's, where depending on which kind you buy, a packet of 50 seeds sells for about $25. It's more expensive than regular seed, but based on the literature, it's worth it. Plants tend to produce 30 to 50 percent more fruit, and they start producing earlier. They also produce later, because they don't succumb to the host of diseases most tomato plants do by early fall. When Joe was getting started he read to expect a 75 percent attrition rate for a first timer, so he planted 96 rootstock plants. Instead, after grafting he had a 75 percent success rate, so he gave away his surplus seedlings to gardening friends around New England. In return, they're reporting to him on their success, and how the grafted varieties compare to the regular varieties in their gardens this season.

The grafting process itself is fairly simple. (There's a great tutorial from Johnny's over here.) You plant the seeds. You wait until the stems are about 2 millimeters in diameter. Then you cut the rootstock plant, cut the fruit plant, and use a plastic clip to hold the stems together. The critical period lasts about seven days, during which time the plants need to be kept very humid so that the vascular system of the upper plant doesn't try to draw too much water through the healing scar. If the plant lives through this time, you're in the clear. 

Joe says he picked up a few tips through trial and error—he learned to plant the rootstock and fruit plants at different times, because they grow at different rates but need to be the same size for grafting. He also says he lost about three weeks in his planting schedule from the project, so next year he'll start that much earlier. Finally, he learned to plant the scar of the plants above ground, because you want only the rootstock plant growing roots. 

He also found out you can graft eggplant seedlings onto disease resistant tomato rootstock, so that may be next year's experiment. In the meantime, he's eagerly awaiting the harvest. We'll check back in come August to see how the fruit turns out! Have you ever planted a grafted veggie plant?


Anonymous said...

Broke a tomato plant and grafted it back to its own rootstock and it worked. This made for a great lesson in gardening class about not giving up when you think things are broken!

Kim Allsup
gardening teacher
Waldorf School of Cape Cod

Elspeth said...

wow Kim thank you for sharing! a good lesson indeed.


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