Terence Robinson1, Steve Hoying2, and Robert Andersen1 1 Dept. of Horticultural Sciences, NYSAES, Cornell University, Geneva, NY 14456 2 Dept. of Horticultural Sciences, NYSAES, Cornell University, Highland, NY 12528
Edited, adapted and commented by Carlos J. Tapia T. Technical Director of Avium and Content Director of SmartCherry. 2019
In recent years there have been a number of advances in cherry cultivation, including the introduction of less vigorous rootstocks, new varieties, high-density training systems and covers for control of cracking rain, etc., which are helping to solve the major problems affecting cherry growers in the eastern United States and the rest of the world.
While producing cherries using dwarf rootstocks and high-density orchards remains a challenge, several management techniques have been developed over the last 10 years to overcome this challenge.
Plant high densities.
Fruit orchard yields are strongly related to tree planting density. Low yields from traditional cherry orchards can be substantially improved with high-density orchards, yet growers have little experience with high-density cherry orchards.
“A concrete example today is the comparison between a “traditional” system at 4 x 2 m. with a density of 1,250 plants/ha, with a higher density system at 4 x 1.5 m.; 1,667 plants/ha. Although there is a difference of a little more than 400 plants between both, this number does a great job in terms of precocity, increased potential and sustained maintenance of this potential over time. The great difference in general is in the investment for the greater number of plants of around US$$3,000/ha extra, an investment that plays in favor of the favorable critical points described above.” says Carlos Tapia.
In this study, 5 high-density production systems on standard and dwarf cherry rootstocks were compared over the last 8 years. Among the six systems tested, the highest cumulative yield/ha over 8 years was with the vertical axis system (69 tons/ha), followed by the Slender Axe and “V” systems (59 tons/ha), the Spanish goblet system (47 tons/ha), and the traditional central axis system (32 tons/ha).
Yield differences between systems were largely a function of tree density. There was a linear relationship of tree planting density and yield (Fig. 1). The Vertical Axis system had a higher cumulative yield than expected from its tree density. The large differences in yield resulted in a 3-fold difference in cumulative crop value between the Vertical Axis system and the traditional low-density central axis system. With current rootstocks, new cherry orchards should be planted at densities of at least 700 trees/ha and with new developments we envision orchards of up to nearly 2,000 trees/ha.
Dwarf rootstocks
Trees in 'Gi.5' are significantly smaller (21%) than trees in 'Gi.6' which in turn are smaller by about 9% than trees in 'MXM.2'. In addition, Gisela trees had a more 'calm' appearance, making them more suitable for high planting densities. We estimate that trees in Gisela 5 should be planted at densities of 1,000-2,000 trees/ha, while Gisela 6 should be planted at densities of 750-1,200 trees/ha.
The rootstocks had a major influence on the crop in the first 8 years of the research. With the Hedelfinger variety, 'Gi.5' had the highest cumulative yield (57 kg/tree) while 'Gi.6' was intermediate (49 kg/tree) and 'MXM.2' had the lowest yield (13 kg/tree).
‘Gisela 5’ trees had 10 times the yield of vigorous ‘MxM.2’ trees in the fourth year and 4 times the cumulative yield after 8 years. ‘Gisela 6’ trees had approximately 7 times the yield of ‘MxM.2’ trees in the fourth year and 3.5 times the cumulative yield after 8 years. However, in ‘Gi.5’ they were excessive as the fruit size was reduced compared to Gi.6.
With ‘Hedelfinger’, ‘Gi.6’ trees had larger fruit size and higher fruit soluble solids than standard sized ‘MxM.2’ trees. In contrast, ‘Gi.5’ trees had larger fruit size and lower soluble solids than ‘Gi.6’ trees. With fruiting varieties such as ‘Sweetheart’ and ‘Lapins’, trees in Gi.5 had excessive loads that will require management through pruning or thinning to achieve better fruit size.
Modified pruning strategies such as branch thinning and/or annual topping will be required to achieve marketable fruit size with Gi.5 and highly fruiting varieties.
New varieties
The performance of cherry varieties in eastern North America can vary widely due to soil and climate differences. Our suggestions for new cherry varieties are those that have performed well in our research orchards.
Early varieties
Cavalier™ (Rynbrandt cv.) – This early-maturing cherry has medium-sized, firm, high-quality, dark red fruit. It should be planted on Gisela rootstocks as it has low productivity on vigorous rootstocks. Bacterial canker tolerance and winter hardiness are good, as is resistance to cracking. Self-infertile, in Pollen Group IV (S2S3), with an early flowering season; multiple pollinators are recommended.
Chelan® – This early maturing cherry has moderate quality, dark mahogany red, firm fruit, moderate to large in size. For best flavor, the fruit should be allowed to fully ripen. Productivity is very good, crack resistance is fairly good, and trees are resistant to powdery mildew. Self-infertile, in Pollen Group XVI (S3S9), with an early flowering season.
Kristin – This early to mid-season ripening cherry has moderately sized, firm, dark red, flavorful fruit. Winter hardiness is excellent, and the fruit has moderate to good resistance to rain-induced fruit cracking. Self-infertile, in Pollen Group III (S3S4), with an early to mid-bloom season.
Mid-season varieties
Benton® (Columbia) – This mid-season ripening cherry has large, firm, dark mahogany red berries with very good flavor. Yield has been consistently high in trials in New York. Crack resistance is quite good. It is self-fertile, with a mid to late flowering season.
WhiteGold® – This mid-season ripening blush cherry has light yellow flesh with a yellowish-red skin blush that is firm, moderate to large in size, good flavor. Trees are very productive, cold hardy, and well adapted to eastern North American growing conditions, with very low susceptibility to cherry leaf spot and bacterial canker. Fruits are moderately rain tolerant. Self-fertile, with a mid to late blooming season.
Glacier® – This mid-season ripening cherry has very large fruits that are dark mahogany red with very good flavor, but less firmness than other fresh market varieties. "Glacier" could be an excellent fruit for local fresh markets. Should be grown on early rootstocks that control size. Moderately susceptible to rainfall. Self-fertile, with a mid to late blooming season.
Lapins – This mid-season ripening cherry has large fruit that are dark mahogany red with very good flavor and excellent firmness. Lapins produces exceptional fruit for immediate local sales. It has had surface pitting problems when shipped from the West Coast. In New York it also suffered from winter injury in 2003 and 2004. However, it is a productive, self-fertile, exceptional variety that is quite tolerant of rain.
Late varieties
Regina. This late-ripening cherry is the most promising new variety for the East. Fruits are large, dark red, very firm with a long stem. It is fairly rain tolerant. It is a late bloomer which helps it escape frost, but it requires a pollinator variety that is also a late bloomer. Hudson, has done very well in our trials in Geneva. It is a shy cultivar unless grown in one of the Gisela populations. It is a late bloomer.
Sweetheart – This very late-ripening season cherry is best for late season. Fruits are of very high quality, bright red, firm and have good flavour, but size is moderate. A very easy tree to grow, with a spreading tree form and early, heavy crops on all rootstocks. It has good winter hardiness and bacterial canker susceptibility and the fruit is moderately resistant to cracking. The tree is self-fertile, with mid-season flowering. On Gisela rootstocks it is often over-productive and requires crop load management to achieve acceptable size.
Keeping trees alive.
The saying goes that “cherry trees love to die.” With heavier soils often cherry tree survival is poor. There are 4 major management approaches that have been used to limit tree mortality.
Use of ridges. Cherry tree death is often associated with winter damage and excessive soil moisture. In some cases, death is caused by root rot. PhytophthorIn other cases it is caused by a winter injury and subsequent infection with bacterial cancer.
It is evident that the use of flower beds improves the experience in this type of soil, but it is assumed that this type of “tool” will be used for the rest of the life of the orchard in operational terms in pruning and harvesting tasks.
This is probably due to better oxygen levels in the soil and reduced waterlogging in the fall and spring. An important note is that trees planted in raised beds can dry out quickly in the hot summer compared to flat soil.
Intensive soil use. Winter damage to cherry trees is often associated with wet areas in a field. The use of intensive cultivation on each row has resulted in much less winter damage to cherries. Various types of “grasses” such as grasses or legumes can be used to remove excess moisture in the fall and spring.
Use resistant rootstocks. None of the currently available cherry rootstocks are resistant to Phytophthora root rot; however, Gisela rootstocks show greater tolerance than Mahaleb, MaxMa, but perhaps not more than Colt.
Bacterial canker control. In the humid climate of various parts of the world in cherry producing areas, it is important to plant varieties that are less susceptible to bacterial canker. In addition, 3 management practices are important to prevent tree death due to this disease. (a) Pruning should be delayed until growth begins in spring or all pruning should be done in the postharvest period. However, this last practice limits having a seasonal history to perform a pruning operation based on cold storage characteristics, bud quality, etc. (b) use a copper spray program that includes 2-3 sprays at leaf fall (20% leaf fall and 90% leaf fall) and 2-5 sprays in winter until bud swell. (c) never make cuts flush with the axis. Always leave a 10-12 cm “wad”. If the canker gets into this patch, it will slowly advance toward the trunk, but will not infect it directly.
Formation of young trees.
Traditionally, cherries receive little training and pruning for the first five years.
However, with high-density orchards, investments in proper tree training pay dividends. Also, starting with the right tree will result in greater early production. This has been amply demonstrated over time.
Plant a high-quality tree. The optimal tree to plant differs by system. For Vertical Axis systems, a large, bud-bearing tree is best and requires little pruning and training during the first few years.
The larger, earlier-bearing tree used in the Vertical Axis and Thin Spindle systems has a much higher production in the third and fifth years than a smaller-sized tree. For bush and “V” systems, for example, a medium-sized tree is better since these systems employ a significant predominance of the leader in the planting.
“In Chile, there are still no successful experiences with trees finished with the presence of early shoots. It is thought that, by having early shoots, the homogeneity of the plants is limited. However, a number greater than 5 of these early shoots could generate a “plus” in the precocity of a high-density plantation. In any case, when this idea is raised, it is that these early shoots are homogeneous in vigor and always thinking about the use of medium to low vigor rootstocks.” said Carlos Tapia.
Minimize stem pruning during the first few years. Repeated pruning cuts in the first 3 years reduce yield, while minimal pruning during the first 3 years results in high early yield. This means that one-year-old branches should not be pruned.
Developing untopped lateral branches to successfully incorporate minimal pruning in young cherry trees requires specialized branching techniques to overcome strong apical dominance.
This technique allows for minimal pruning but proper placement of limbs along the leader. Bending branches flat. Cherry trees are very apically dominant, resulting in vertical branch angles.
Management of an adult cherry orchard.
High density mature cherry trees on dwarf rootstocks have 2 main problems: dense canopies with too little light in the lower canopy and possible excessive loads with small fruits.
What is suggested to overcome these problems:
Aggressive pruning. We suggest that mature trees, especially in series such as Gisela, be pruned more aggressively than trees on more vigorous rootstocks. Pruning should include the removal of most of the fine, shaded wood each year, as well as the permanent renewal of coarse, unproductive material on young wood.
Maintain light exposure to the lower part of the tree. In high density plantations it is very easy to allow very thick canopies to develop. Cherries need good light distribution to the lower part of the tree to produce good quality fruit and healthy shoots for the next season's harvest.
The best exposure to backlighting is best achieved by limb renewal pruning. The removal of 1-2 large branches in the top or middle of the tree each year, prior to flowering or after harvest, depending on the objective of the harvest, renewal or removal, respectively.
Conclusions.
Considering yield, fruit size, soluble solids and gross economic yields, the central axis systems, both traditional and modified, were the best systems in this test, but not the more bushy training systems.
High-density orchards combined with a group of management strategies we call “The Integrated Cherry Production System” can result in consistent production of high-quality cherries. The essential points of the integrated system are: high tree densities (>300), dwarf or semi-dwarf rootstocks, new varieties, platbands and inter-row planting when necessary, and “minimum pruning” during the first 4 years, plus renewal pruning of branches to improve light, distribution within the canopy, aggressive pruning to increase fruit size, irrigation, GA applications, and more.3 to improve the firmness of the fruit and other cultural and nutritional management to support this system over time.
Figure 1. Relationship between tree planting density and cumulative yield of 3 cherry varieties (Hedelfinger, Lapins, Sweetheart) on MXM.2, Gisela 5 and Gisela 6 rootstocks, independent of the training system.
Figure 2. Relationship between tree planting density and the cumulative profitable crop value of 3 cherry varieties (Hedelfinger, Lapins, Sweetheart) on MXM.2, Gisela 5 and Gisela 6 rootstocks, independent of the training system.
