When planting a grafted tomato, keep the graft at least 1 inch above the soil surface. © Jo Ellen Meyers Sharp
Last year, grafted vegetables, especially tomatoes, showed up on garden center tables. It’s not the term grafted that attracted people’s attention as much as the cost, frequently three times what you’d pay for a regular tomato in the same size pot.
We’ve been planting grafted plants, such a tea roses and apple trees, for centuries. In the 1920s, the Japanese and Koreans started grafting vegetables, especially tomatoes and other plants in the same botanical family. Interest started here in the United States in the 1990s.
The grafting process is pretty much the same, whether it’s an apple tree or a tomato.
A grafted plant has two parts, rootstock and scion. The rootstock is selected because it provides disease resistance, boosts production or has other characteristic that support the top part of the plant, called the scion. The scion is selected for the taste, size of fruit or other attributes it produces.
Under laboratory-like conditions, the two pieces are grafted together and held in place with a clip or other device until the wound heals.
Last year, I grew a grafted Black Krim and a regular Black Krim heirloom tomato side by side. I wish I could report some observation other than last year was a terrible tomato year for me.
The grafting process is of particularly interest with heirloom tomatoes, which lack disease resistance and mature late. A grafted heirloom tomato would have the disease resistance we want and better and earlier production. I’m going to them again this year with Brandywine, another heirloom.
A lot of savvy gardeners remove all but the upper-most leaves and plant their tomato transplants deep in the soil, or to dig a trench and plant them horizontally. This encourages good root development along the stem that is underground.
However, you can’t plant grafted tomatoes this way. The graft, usually marked with a plastic clip, must stay at least 1 inch above the soil surface. If the graft is below the soil grade, stems from the rootstock will emerge and overwhelm the scion, defeating the purpose of graft.
This labor-intensive process is why the cost of grafted vegetable plants is so much higher. But, if production is boosted considerably, you could get by with fewer plants, something that might offset the cost. Or, you can splurge on one grafted tomato and grow it side by side the same type of regular plant and do your own little experiment.