Cherry rootstocks of the future
Krymsk rootstocks are intermediate between the standard Mazzard and the extremely productive Gisela.
Smaller, more precocious cherry trees reduce labor costs and recoup investment sooner, says educator Lynn Long.
Published January 15, 2011
While many Pacific Northwest cherry growers are still planting trees on Mazzard, growers in the Mid-Columbia region are planting on the productive and precocious Gisela or Krymsk rootstocks because of concerns about labor. By developing pedestrian orchards, some growers have reduced their labor needs by 30 to 50 percent, Lynn Long, Oregon State University Extension educator, reported during the Washington State Horticultural Association’s annual meeting.
There are other economic benefits, too. Studies have shown that it can take only eight years to recoup the investment in an orchard on the precocious Gisela rootstock, compared with 15 years for an orchard planted on the standard Mazzard, he said. “Mazzard is a rootstock of the past; these other rootstocks are rootstocks of the future,” he added.
There’s been concern that trees on Gisela rootstocks produce small cherries, but Long said trees on Gisela can produce large fruit—sometimes larger than those on Mazzard—with the right pruning and crop load management. In his experience, trees on Mazzard produce the lowest yields and G.6 produces the highest. Ideally, he would like to find rootstocks somewhere in between, he said, because it is easier to control the leaf-to-fruit ratio (which is important for fruit size) if the tree is not trying to overproduce all the time. He thinks the Krymsk 5 or 6 rootstocks might fit the bill.
Growers are looking for a rootstock that might give higher yields with Regina. The Regina cherry has been widely planted in Oregon, though much less so in Washington State, perhaps because of its reputation for not being very productive. Long said Oregon growers have been harvesting five to six tons per acre from Regina when it’s planted and grown properly. It gives high packouts, even after rain, so it’s something of an insurance policy.
In a trial with Regina on Krymsk 6, the trees have been producing higher yields than on other rootstocks, and Long said he would continue to track production.
Mazzard still could have a place with some of the more productive varieties, such as Sweetheart, Lapins, or Chelan, he said, or if the planting is on infertile soils. “But I would not use Mazzard for anything else.”
The Colt rootstock from East Malling is not dwarfing and is similar to Mazzard. It could be used in replant situations where fumigation is not an option. It is resistant to bacterial canker, which would be an advantage in wetter areas with high disease pressure.
The semidwarfing Maxma14 rootstock, developed in Oregon, is a moderately productive rootstock for growers who want to avoid paying high royalties for something more precocious than Mazzard. It should not be used in heavy soils, for very high-
density plantings, or if fruit size is of primary importance, Long advised.
The dwarfing G.5 is one of the more popular rootstocks throughout Europe and is suitable for very high-density plantings, such as the UFO (Upright Fruiting Offshoots), or if the grower wants to advance harvest by two to three days. It is good for less productive varieties, such as Regina and Tieton.
G.6 is the most popular of the productive rootstocks. It is good for moderately high-density orchards with 300 to 500 trees per acre. With some varieties, it is weaker than G.12, and it is most suitable for varieties with low to moderate productivity. “Don’t use it if you don’t understand the principles of productive pruning,” Long urged. “Be cautious with productive varieties.”
There’s a question about its compatibility with Attika. For that variety, use G.12 instead.
G.12 provides more vigor in a productive rootstock. It is easier with G.12 to maintain fruit size than with G.6. It is good with Regina and has good anchorage.
K.5 has been used in The Dalles, Oregon, for about ten years. This would be a good choice for a grower wanting a productive tree of higher vigor, about the same size as G.12. It is less productive than G.6 or G.12, but it is easier to manage an appropriate balance between fruit load and the number of trees, which is important in sizing cherries. It is successful with Regina, Lapins, Chelan, and Skeena and is more forgiving than G.6. It seems to be well acclimated to hot areas and suffers less heat stress than Gisela. It is reported to be hypersensitive to viruses that are common in the Pacific Northwest but dies quickly before the virus can spread. The Krymsk rootstocks are a less expensive option than Gisela because of lower royalties and fees.
K.6 produces a productive tree of moderate vigor. It is good for Regina and suitable for hot climates.
For more information, see the Pacific Northwest Extension publication Sweet Cherry Rootstocks for the Pacific Northwest, written by Long and Clive Kaiser, which can be found on the Web site http://extension.oregonstate.edu/wasco/rootstocks.
Long has also written an Extension publication called Four Simple Steps to Pruning Cherry Trees on Gisela and Other Productive Rootstocks, which is available in English and Spanish at http://extension.oregonstate.edu/wasco/horticulture.