Heirloom varieties, such as the yellow-orange and rosy-yellow ones shown, benefit from being grafted onto disease-resistant rootstocks, which can also increase their yields.
Cut the rootstock at an angle in one direction three-quarters of the way through the stem.
Then cut the scion at the same angle in the other direction.
Attach the plants at the cuts, then use a spring-loaded clip to hold the plants together
The rootstock and scion are joined, held in place by a spring- loaded clip.
John is holding an Amana Orange heirloom, a beefsteak with intense flavor.
Place the rootstock and scion side by side to match up the diameter of the stems.
Cut the plants at the same angle.
The rootstock is cut in half.
Slide the scion into the clip that is attached to the rootstock.
Place the scion stem into the clip so the angles match.
A newly top grafted tomato.
Tiny silicone clips used for grafting.
John Grisak with a freshly harvested tomato
Grafted tomatoes are all the rage lately because they boast increased production and disease resistance. You can find them at local nurseries, as well as in mail order catalogs, but they come with a hefty price, ranging from $7 to $12. A lot of gardeners want to know if they’re worth it.
While it sounds high-tech, grafting is an age-old method of splicing together plants to provide beneficial qualities to the scion (or top plant) from the rootstock. (Editor’s note: See Amy’s article on grafting fruit trees in TNP #177.) For example, most of the apple trees we have are grafted, because if we grew them from seeds we’d typically have what growers call “spitters” with barely palatable apples.
Why Graft A Tomato?
Long ago, growers discovered that you could splice a good-tasting variety (or several of them) on a hardy rootstock to create a tree that is resilient and productive. Grafting tomatoes is the same concept, just in an annual plant form.
It makes sense to graft a tree since they take years to mature and produce, so why graft a vegetable plant? Gardeners understand the importance of rotating crops in order to prevent disease, yet with the increased use of high tunnels in commercial tomato production it’s not always possible.
According to Judson Reid, Extension vegetable specialist at Cornell University, after a few years of growing tomatoes in the same space, these growers noticed a significant drop in production due to soil-borne diseases such as the Fusarium and Verticillium pathogens. And heirloom tomatoes, which are very popular on the market, are often particularly sensitive to these diseases.
To remedy this situation, horticulturists developed hybrid rootstocks specifically for grafting that are resistant to the numerous common diseases. This way, growers can graft the desired tomato variety on this high-powered rootstock in order to withstand the disease issues.
The good news is that besides disease resistance, the plants demonstrate increased production, which is the primary reason home gardeners turn to grafted plants. Reid says, “A vigorous scion may respond more to a vigorous rootstock, particularly with heirlooms.” Many growers claim up to 40-percent greater yields.
Four years ago, I learned about this technique, which caught my interest because, with our short season, my goal is to grow as many tomatoes as possible in my limited space. I grafted my aunt’s favorite, the Brandywine (a variety that originated in the Midwest, but it doesn’t do nearly as well here with our cool summer nights), on a Maxifort hybrid rootstock.
I planted the variety in my little greenhouse alongside an un-grafted Brandywine. The results were impressive. We were picking red Brandywines by the end of July, and the single grafted plant took over the greenhouse. By August I had to crawl underneath it to reach anything beyond it. Since I have limited space in the garden, if I can plant half the number of plants for the same amount of tomatoes at the end of the season, it’s definitely worth the investment.
It may seem odd, but fall is the time to get started on grafting tomatoes for next year. You need to order your rootstocks for next spring because nurseries grow a limited number and they sell out quickly. You should also order your supplies, and practice grafting stems of old tomato vines or something similar. Once you get the hang of grafting, it’s easy, but it can take time to acquire the skill.
If you don’t want to pay the hefty price tag for a retail grafted tomato, grafting tomatoes at home can be more economical and only requires a few materials. You’ll need a rootstock and your favorite variety for the top plant, some sort of clip to attach the rootstock and the scion, clean containers, fresh potting soil, a razor or utility knife (or one of the nifty grafting knives available), a skewer or stick support of some kind, and a plastic bag large enough to go over the plant to act as a healing tent.
The clips are what hold the plants together. I’ve heard of people using tape, but it is unwieldy to try to hold the plant together while taping, and it can harm the plant when you remove it. These clips make it fairly simple to join the plant halves. If you are top grafting small plants, you can use a 1.5mm or 2mm silicone clip, which simply pinches open and slides over the rootstock, providing a tube where you attach the two plants. For plants with stems larger than 2mm, or with a side grafting technique, go with the clothespin-type clips, which have a little spring. These give you much greater latitude on the size of plants you can use.
Buying the clips can be an investment. The silicone clips range from $15 to $20 for 200 clips, and the spring-loaded clips are more than double that. But you’ll have them for years, or you can mitigate the cost by dividing an order among friends.
The Right Rootstock
The most important piece of the grafting puzzle is the rootstock. People often wonder if you can just use a normally vigorous tomato variety. I can’t stress enough that the key to successful grafting is the rootstock. If you don’t use the specialized varieties that are grown for their incredible vigor and disease resistance, then there’s no point in doing it at all.
There are more rootstock varieties on the market each year, but Maxifort remains my favorite. With its vigorous growth on my indeterminate plants (particularly Brandywine and Amish Paste), the growth rate and production is impressive. Other options include Estamino, which works well in areas with a shorter growing season or with small-fruited varieties, or Colossus, which boasts both dynamic growth and marked disease resistance to soil-borne pathogens.
Related Stories: Farm-To-Table with the Gallatin Grown Farm
Save With Seeds
As expected, the cost of these rootstock varieties is more than a typical packet of tomatoes. They can range anywhere from $23 to $28 for 50 seeds. When you look at what it would cost you to buy even a couple of plants, it is more economical to graft your own. Or, as with the grafting clips, you can share seeds with family and friends.
Whether you are top or side grafting, the beginning is the same. Start your rootstock and scion varieties at the same time, in clean containers with new potting soil, roughly 12 weeks prior to when you will set them outside.
To top graft, you need to work with the plants when they’re smaller since you need the silicone clips to fit over the stems. Carefully remove a rootstock plant and a scion, and place them on a cutting surface. Line up the stems so they match in diameter.
Taking your knife or razor, cut the stem at roughly a 45-degree angle. Immediately toss away the top of the rootstock plant. (I’ve made the mistake of not doing this and grafted the plant back together!) Do the same with the roots of the scion.
Now pinch open the silicone clip and place it over the rootstock section, leaving half the length of the clip available to receive the scion. Slide the scion into the clip, matching up the angles of the cuts so the plants can grow together. Plant this newly joined plant in a different container with moistened soil.
Use a skewer to support the plant, mist with water and place a plastic bag over the top to create a humid environment. Place it in a warm place out of direct sunlight. Keep it there for about four to six days. The plant should obviously be growing (if it wilts, you have a problem). After the four to six days, remove the plastic bag and give it another few days before setting it under lights. Water, if necessary.
Side grafting is a bit easier and has a higher success rate, but it does take a little finesse to make the cut just right. You will want larger plants (at least 2mm). Start the same way as you did for top grafting, by removing a rootstock and scion plant, and set them side by side on a cutting surface. I often trim off the top, leaving a few leaves of the rootstock plant just so I know which is which.
The cut is the big difference. Instead of cutting all the way through, make a cut three-quarters of the way through the stem at roughly a 45-degree angle in one plant. Do the same with a cut in the opposite direction in the other plant. Join them together, and use the spring-loaded clip to hold them in place. (If you cut the plant in half, like I sometimes do, you can try top grafting it.)
Carefully plant both plants in a container. The reason why there is greater success with side grafting is because the roots of both the plants are growing. It usually takes a full week for the joint to grow together before you can safely remove the clip. After this point, you can finish trimming off the top of the rootstock variety and cut off the roots of the scion.
When you plant grafted tomatoes in the garden, be sure to give them plenty of room. Unlike planting typical tomato plants where you bury the stem, do not plant the graft below the soil line or you will have the rootstock take over, negating the purpose of grafting.
Tomato grafting is ideal for gardeners who don’t have a lot of space but want to grow a fair number of tomatoes. Plus, it’s just another technique that keeps gardening interesting.
Simply put, it is just plain fun!
For More Grafting Goodies
JOHNNY’S SEEDS: You can find
supplies and videos of tomato grafting
at Johnny’s Selected Seeds online by visiting johnnyseeds.com
CORNELL VIDEO: Judson Reid, with Cornell University’s Cooperative Extension Vegetable Program, also has an excellent video tutorial on You Tube. Check it out at youtube.com/watch?v=08YfqCpL3po.
This article originally published in THE NEW PIONEER® Fall 2014 issue. Print and Digital Subscriptions to THE NEW PIONEER® magazine are available here.
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