Bob Westerfield is an extension horticulturist.

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Two for One Tomatoes
by Bob Westerfield       #Edibles   #Propagation   #Vegetables

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

An actual grafted tomato in our research garden.

If you took a survey of home gardeners and asked them about their favorite vegetable to grow, most likely the tomato would be at the top of the list. Anyone who has grown tomatoes knows that the quality and flavor of homegrown far surpasses that of a store-bought tomato. Anyone who has spent time growing tomatoes also knows that at times they can be finicky and be a challenge, even for the most experienced gardener. If you happen to cherish the more flavorful heirloom varieties, you face even greater challenges when it comes to disease, insects and cultural problems. While the practice has been around for centuries, grafting has more recently become the rage in growing difficult tomato varieties more successfully. With the difficult task of growing these older varieties, grafting may give you the edge to get the job done in your garden.

A cleft graft on the scion with a tapered wedge cut at dual 45-degree angles.
 

The correct way to cut a splice graft. Both the rootstock and scion are cut in opposing matching angles.
 

Rootstock cut using the cleft method of grafting. A ¼-inch cut into the rootstock is made into which the scion wedge cut will be inserted.
 

Ensure the diameter of the rootstock matches that of the scion. This is on a splice graft.
 

Connect the rootstock of cleft graft to scion.
 

Graft held together by a grafting clip.

Vegetable grafting is a centuries-old technique used to improve plant production, reduce disease and improve plant vigor. Asia and Europe have been leaders in vegetable grafting for years but has only become popular in the United States over the past ten years or so. Most garden catalogs now include grafted varieties of tomatoes, eggplants and peppers along with some other varieties. Just look at the price of these plants and you may decide they produce vegetables made of gold. It is not uncommon for small grafted plants to sell between $12 and $16 dollars. The extra cost comes in the production of grafting two different varieties of tomatoes onto one. Purchasing a grafted tomato is certainly one way to go, but the process is really not that difficult once you understand a few basics. By following a few steps you can begin to graft your own varieties, save money and have fun at the same time.

Grafting is simply taking the top portion of a tomato variety, called the scion, and connecting it to the bottom half and root system of another tomato plant, called the rootstock. The top portion of the graft produces the flavorful and desirable tomato that you are after –perhaps one of your heirloom favorites. The rootstock provides protection from tomato viruses, diseases, nematodes and other common problems associated with tomatoes. Commercial nurseries often use a standard rootstock you won’t find in garden centers that provides a hardy base for the top portion of the graft. It is perfectly fine, however, to use the rootstock of favorite hybrid tomato you may like such as ‘Beefsteak’, ‘Better Boy’, ‘Amelia’ or some similar hardy variety. The scion portion, or top, being difficult to grow on its own might be an older variety such as ‘German’, ‘Homestead’ or other heirloom variety. In essence what you are doing is exactly what they do with most fruit trees. You are grafting two plants together to get the best of both worlds.

They key to successfully grafting tomatoes or any other vegetables, is to select rootstock and scion that are very similar in diameter. In order for a successful graft to take place, the cambium (area just under the outer skin) of the rootstock and scion must be aligned and in contact with one another. You can purchase transplants for both your rootstock and scions or you can start them from seed. If you are only going to do one or two grafts it may be easier to buy the plants to start with. If you are doing several trays of grafted plants it would be cheaper to seed them and grow them out yourself. It is best to work in a sterile environment, cleaning off your working surface with a light alcohol-based cleaning solution before starting your grafts. Use a clean, sharp razor blade for your cuts.

There are several different methods of cutting your stock depending on the grafting technique you choose. Cleft grafting, otherwise known as wedge grafting, is a common way to graft tomatoes. It basically involves cutting the root stock section horizontally just under the first set of leaves. You should be left with a root system and stem 1-2 inches long. Make a small ¼-inch vertical incision into the center of the rootstock cut. The scion stem should be similar in diameter to the rootstock and then cut into a wedge shape 1 inch or so below the lowest leaves on the stem. The wedge should be about ¼-inch long and is inserted into the ¼-inch slit of the rootstock. Carefully hold these two together while using a plastic grafting clip or grafting tape to secure the two together.

Another type of grafting is called splice grafting. Both the rootstock and scion of matching diameter are cut at 45-degree angles and clipped together with a grafting clip. Splice grafting is easier to do and faster than cleft grafting. Cleft grating however holds the scion more tightly than splice grafting.

After all of the grafts are complete, use a misting bottle to lightly spray the plants to provide them some moisture. Take a final look to see that all the grafts are tight and properly aligned. Cover the plants with a plastic tent or small plastic bag over each container, keeping the plastic away from touching the foliage of the plant. Spray additional moisture inside the plastic to create a slightly humid environment. Place the plants out of direct sunlight, in a temperature between 65-70 F and allow them to rest for two days. On the third day after grafting, carefully lift the plastic and spray just enough water inside to raise the humidity and close the plastic chamber again. Allow the plants to continue to heal for another day and on the fifth day open the plastic up for 30 minutes and once again spray inside the plastic chamber to create humidity. On the sixth day remove the plastic for one hour and then spray the chamber inside the plastic well and close up tightly. On the seventh day remove the plastic for a period of six to eight hours once again returning it after spraying the inside with water. On the eighth day you will totally remove the plants from their protective plastic cover.

Although the scion and rootstock will begin to establish a connection at approximately seven days, it takes about 14 days for the grafting to fully heal. After you remove the plants from the plastic allow them to rest in a room about 65 to 75 F from one to two days to harden off. Begin to put the plants outside to acclimate them to the outdoors for four to seven days before transplanting. Be sure to provide moisture and don’t allow them to dry out. When transplanting into the field you can remove the grafting clips and use small ¼-inch-diameter sticks to help support he tender developing plant. Be sure when transplanting that the graft union remains above the soil line. If it becomes dirty, the scion will root into the soil and any advantages that would have been provided by rootstock will be nullified. Check the plant regularly and look to see that the rootstock also does not sprout out of the ground. Pinch it off before it begins to develop to allow the scion portion to take over.

I have grafted tomato plants in my research trials with the University of Georgia and have had some pretty good success. While I cannot say that grafting is the silver bullet to prevent all disease and other issues, it does seem to have its place with difficult to grow varieties. If nothing else, grafting is a unique look at how many plants are grown commercially and it is fun to see the science first hand at how it is done. Give grafting a try this season and hopefully you will have a delicious crop for your efforts.

 

A version of this article appeared in an April 2015 print version of State-by-State Gardening.
Photography courtesy of Bob Westerfield.

 

Posted: 03/30/18   RSS | Print

 

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COMMENTS

gpaesa@aol.com - 04/07/2018

Bob - Please help me get this message to Sid Mullis. I’ve tried every avenue I can find to get to him to no avail. In the Feb ‘18 issue of Georgia Gardening Sid makes reference to ridding North Georgia cool season grasses such as Fescue, of the dreaded Poa Annua, with the Herbicide imazaquin. I can find no source of imazaquin for fescue lawns anywhere. Sid, or Bob, please advise of a source of imzaquin. Thanks for all the good work you both do.

Gene Austin. Email .(JavaScript must be enabled to view this email address)

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