Who wouldn’t want vegetable plants that are stronger, healthier, and better equipped to deal with stress? That exactly describes some of the benefits of grafting, a technique that has been used in the tree fruit industry for years, but is recently gaining momentum in vegetables. (To read more about how grafting can limit disease, salinity, and stress, go to http://bit.ly/14SlJta.)
Grafting is defined as a process that includes splicing the shoot of a particular variety to the roots of another. The splicing makes an immediate hybrid that tends to be more vigorous and tolerant of soilborne disease, nematodes, and other types of stress than the variety that was not grafted. The process is beginning to gain momentum with some growers.
Just ask Kaitlin Dye, owner of Re-DiVined, a company dedicated to grafting vegetable plants. Located in Holtwood, PA, Re-DiVined grafts tomatoes, watermelons, and peppers.
In addition to creating strong and healthy plants, Dye notes that grafting helps increase fruit size. “You are going to see larger fruit sizes, better fruit quality, and a prolonged season because the plants won’t go down as quickly,” she says.
Starting Out Small
A graduate of North Carolina A&T University with a degree in soil science, Dye began grafting tomato plants in 2009 for Steve Groff of Cedar Meadow Farm, also in Holtwood, PA. Groff operates a 200-acre vegetable farm and is known for his permanent cover cropping system, which includes no till, the use of cover crops, and crop rotation.
In addition to supplying Cedar Meadow Farm, Dye has customers in Virginia, Michigan, New Jersey, New York, and Ohio who mostly request grafted tomatoes. She also has sold plants in Texas, Indiana, Maryland, and North Carolina.
Tomatoes For High Tunnels
In the case of tomatoes for Cedar Meadow Farm, the operation typically plants 8,000 grafted plants in high tunnels about the third week of April. According to Groff, owner of the farm, he has been using grafted tomato plants for five years, thanks to Cary Rivard, a vegetable Extension specialist at Kansas State University.
“We have to give [Rivard] credit for starting us in grafting,” recalls Groff. “I heard him speak on grafting at the Mid-Atlantic Fruit & Vegetable Convention and I thought, ‘I have to do that.’ We tried 100 plants the first year, and the last four years we have grafted all our tomatoes for high tunnels.”
Groff also cites plant health as the main reason to graft. Specifically, he uses grafted tomato plants to combat Verticillium wilt, which had been a major headache in the past.
“Verticillium wilt race 2 is one of the diseases that is the most influential in the negative way,” he explains. Resistant varieties are available for Verticillium race 1, but for race 2 there are no resistant varieties, he adds.
“With the prolific roots created with grafting, [the roots] out-compete the Verticillium longer and it gives us three or four more weeks of production in contaminated soil,” he explains. “It is because the rootstock is so strong and vigorous, it holds off the disease longer than a plant that has not been grafted.”
In addition to holding off disease, grafting has been compared to fumigation. Groff agrees that grafting does provide the same outcome as fumigation to a degree, but it doesn’t solve all the problems.
“Fumigation is like chemotherapy; it kills the bad and the good organisms,” he explains. “Grafting doesn’t kill anything. It does help overcome some of the bad influences, allowing the crop to perform better.”
Adjusting The Process
When creating these plants for Groff’s high tunnels and other growers, Dye begins planting in the greenhouse in December. The grafting process begins the first week of February.
Last year, she implemented some small adjustments as to how she cares for tomato plants prior to grafting to ensure their health before the process takes place. For example, she now applies nutrition and crop protection products to encourage growth, decrease stress, and prevent bacterial disease.
After grafting, however, when the plants are in the “healing chamber” no fertilizer or water is applied. The healing chamber is where the newly grafted plant must reconnect tissue so water and nutrients can help the scion continue to grow. “The goal is not to encourage top growth but to cut out all stress so the plants can focus on healing at the wound,” explains Dye.
To encourage healing in the chamber, humidity, light, and temperature are regulated. For example, plants in the healing chamber need to receive up to 95% humidity and no sunlight during the first two days after grafting, says Dye. The reason for the ban on light is to stop the plants from “performing photosynthesis and thus calling for more water and nutrients from the roots,” she says. “The increased humidity allows the leaves to be sustained through receiving water from the air until the connection is made.”
After the second day, she gradually allows light in by removing a layer of black plastic — which had been placed over the plants after grafting to reduce light — and using varying degrees of shade cloth. “It is not until day nine after grafting that I allow [the plants] to go into direct sunlight.”
Experience And Cost
According to Groff, the biggest drawback is that it takes education and experience to graft plants. “You don’t just say ‘I’m going to grow two sets of plants and graft them, and then let them grow.’”
The other drawback is the increase in cost. According to Dye, it depends on how many plants are being grafted. On a small scale, the cost would be close to $2 per plant, she says. In Groff’s case, however, the process has paid for itself.
“It only takes a couple pounds of additional fruit from the grafted plant to make up for the cost,” explains Dye. “You should be able to count on a healthy increase in yield, depending on the amount of disease pressure in your soil. In our trial in 2009 [at Cedar Meadow Farm], we showed a 40% increase in yields using grafted over non-grafted. This was with a significant amount of Verticilium wilt pressure.”
As Dye currently does all her grafting by hand, the question remains: Will hand grafting be the norm or will the process become automated in the U.S.? According to Dye, automation will happen eventually, but it won’t happen any time soon.
Mentioning a grafting symposium she attended in Florida late last year that attracted people from around the world, Dye cites the huge volume of one attendee: a grower from Israel who is currently grafting 80 million plants a year.
She adds that in Japan, about 80% to 90% of the vegetable plants are grafted. “Automation will have to happen, as numerous machines have been developed, and we know it works. There will still be challenges growing the plants uniformly, but I think automation will be coming in the future,” she adds.
As for the future of her own operation, Dye says an immediate goal for this year is to graft 30,000 tomato plants. As the business continues to expand, she now
has a small staff helping with the process and follow up. “It is a lot of work,” she concludes, “and I couldn’t do it by myself.”