If we think biotechnology was invented in the 21st century, consider the somewhat bizarre practice of sticking the top of one plant onto the bottom of another: Grafting, this is called, and it’s been around for at least 4,000 years.
Those ancient Greek and Chinese gardeners knew that the right match could produce a plant greater than the sum of its parts — the roots of the first would make the leafy second more vigorous and fruitful.
Many of the woody plants in your garden are grafted, but the idea of growing grafted vegetables at home is new in the United States, with the first plants arriving five years ago in limited markets. It is still too soon to tell whether this is a passing fancy or something here to stay, though mail order catalogues and garden centers are betting on the latter. With each passing spring, they are increasing the quantities of grafted plants and the number of varieties.
The main focus of this phenomenon is the tomato, but this year consumers will also find grafted peppers, eggplant, cucumbers, cantaloupes and watermelons.
“We went from zero in 2009 to over a million this year,” said Alice Doyle, who with partners John Bagnasco and Tim Wada produces and distributes vegetable grafts to wholesale growers and farmers under the brand SuperNaturals.
This year, the enterprise is offering a line of plants that will yield two varieties on one rootstock and a true Frankenstein plant that promises trusses of cherry tomatoes on top and a bed of potatoes below. It is being marketed as Ketchup ‘n’ Fries.
Beyond the novelty value, why would gardeners grow grafted veggies?
Various rootstock hybrids have been developed to bestow different traits, including resistance to a slew of diseases that afflict such popular plants as tomatoes, including blight and wilt pathogens.
Grafts are particularly useful for gardeners who don’t have the space to move plantings from bed to bed annually. Tomato plants grown in the same soil each year will perform fine for four or five years but then will take a tumble as diseases and pests such as nematodes build up, said Steve Dubik, a professor of horticulture at Montgomery College in Rockville, Maryland.
Grafted plants can also achieve other miracles, such as producing more fruit, extending the harvest period and even tolerating hotter or colder climes. The selling point for heirloom varieties such as Brandywine or Mortgage Lifter is that grafted versions fix the general problems associated with antique varieties: poor yield and disease susceptibility.
Chelsey Fields, the vegetable product manager for W. Atlee Burpee & Co., said heirlooms tend to have been developed or discovered by gardeners in a specific locale and may be ill-suited to other regions, climates and soils. “They aren’t necessarily as adapted nationwide as people would like them to be. The thing with grafting is that it really makes them adaptable to all these different environmental pressures,” she said.
Burpee started selling grafted tomatoes in 2012 and now has a dozen tomato varieties for sale and more in the works as they are being trialed, Fields said. “Last year, I dropped Yellow Pear and added in Mr. Stripey, Green Zebra and Marglobe based on garden performance,” she said. This spring, Burpee added three pepper varieties and an eggplant to its catalogue.
The downside to grafted veggies, apart from their added expense, is that their garden performance may not be as dramatically different as billed, and in some cases it’s worse because the highly efficient root system may produce lots of moisture to the fruit but at a cost to flavor.
Jeff Gillman, a horticultural instructor at Central Piedmont Community College in Charlotte, conducted field trials with students and found that when the growing conditions were optimal, the non-grafted tomatoes actually fared better than the grafted ones. In difficult conditions of poor soil and inadequate irrigation, he found that the grafts were superior.
And then there is the cost.
You might expect to spend between $2 and $5 for a conventional transplant, depending on pot size and the retailer. A grafted plant is typically sold in a one-gallon container and retails for $12 or more. If you want to grow a fairly modest five plants, that starts to add up. Burpee sells three in 2 1/4-inch pots for $26.85 plus shipping costs.