The first time I saw grafted tomatoes offered for sale, I thought it was a misprint.
I’d heard of grafted fruit trees or grape vines, but vegetable plants? It fact, it wasn’t a mistake.
Commercial producers have used grafted plants for years with crops such as tomato, eggplant, pepper, cucumber and melons. Grafting is still a relatively new phenomenon for home gardeners. But why go to the trouble of grafting a plant?
There are two big reasons:
1. Prevention of soil borne disease.
By using disease resistant rootstocks, home and commercial growers can reduce or completely avoid pesticide.
2. Increased yields.
Yields up to four times that of the same nongrafted variety of tomato have been reported.
Researchers hypothesize that these disease-resistant rootstocks are more efficient in transporting food and water to the above-ground portions of the plant, resulting in more crops.
It’s important to note that these increased yields are not typically seen in container grown plants.
Grafted tomato plants are commercially available locally, but expect to pay about $10 to $15 per plant.
The concept of grafting a tomato plant is deceptively simple — take the above-ground portion of the tomato variety you wish to harvest, and the root portion of a disease resistant variety, match the cut stems, let them grow together and, voilà, a grafted tomato plant.
Unfortunately, if it were that simple the plants would not retail for $10 and higher.
Grafting tomatoes successfully hinges on matching the diameter of the cut stems of the scion (the above-ground portion you wish to harvest fruits from) and the rootstock. It seems easy enough until you realize that not all tomato seedlings are created equal. Some varieties grow faster and are more vigorous than others.
Any tomato variety can be used as a scion, but rootstocks are usually a role reserved for varieties with known resistance to soil-borne diseases. Some seed companies are developing varieties specifically for rootstock use. But many traditional hybrids have potential for use as disease resistant rootstocks.
Variety names that are followed by a series of letters are resistant to specific diseases. For example, the variety ‘Roma V F N AS’ is bred to be resistant to Verticillium and Fusarium Wilts, Nematodes, and Alternaria Stem Canker. Seed companies are supposed to use one of two systems of abbreviations for noting disease resistance, but I have seen some pretty wide variations. You may need to call the seed company or search online to decipher the codes.
When grafting tomatoes, plan on starting the process at least two weeks before nongrafted tomatoes would be planted.
Grafting is done when tomato plants have two to four true leaves. The scion and rootstock stems are each severed at a 45 degree angle, and the scion stem is matched up with the rootstock stem. The diameters of the stems must be exactly the same diameter for the graft to be successful. A common method for grafting tomatoes is called tube grafting and uses tiny clips to hold the cut stem ends of the two seedlings together for healing.
Following the grafting procedure, seedlings must be kept in a healing chamber, where the humidity is high and the plants are not exposed to direct sunlight. This can be as simple as a frame covered in opaque plastic placed over the grafted seedlings. Ideally, in 2 to 4 days the stems will grow together, forming a new grafted plant.
Some wilting is normal in the first day after grafting. After the stems grow together, successfully grafted plants will no longer show any wilting.
For the following week, plants should be gradually reintroduced to light and lower humidity. It is normal for the grafting clips to fall off as the plants resume growth.
Plants should be monitored closely and gradually acclimated to outdoors just like any other tomato seedling. Take care to plant the seedling with the graft above the soil surface to prevent the scion stem from rooting.
Grafting is a numbers game. Expect many more failures than successes. Plan on grafting way more plants than you actually need. Increase your odds of success by keeping your growing and grafting areas as clean as possible. Use fresh, sterilized potting media. Wash your hands with anti-bacterial soap and use latex gloves and sterile tools when doing the actual graft. Water newly grafted plants from below.
I will try my luck at grafting tomatoes this winter. In the meantime, it is time for the 8th Annual Tomato Taste Panel on Thursday, Sept. 12, at the U of I Extension office in Macon County. We have more than 40 tomato varieties to taste. Tasting sessions will be at 1 p.m. and 6 p.m.
Please register by calling (217) 877-6042.
Jennifer A. Schultz Nelson is a unit educator in horticulture for the University of Illinois Extension.