Mar 4, 2011Plantings are closer, denser than they were 50 years ago
Three Extension educators shared their thoughts on the ways tree fruit growing systems have changed in the last 50 years.
Jerry Frecon, Rutgers University: In the 44 years I have been working with commercial orchards, I have seen a trend toward denser and more intensive orchard plantings in the United States. This conversion has been more complete in apples, but has also been apparent in cherries, pears and, to a lesser extent, in peaches.
Using dwarfing rootstocks and manipulating and managing tree growth have obvious advantages. The greatest is the earlier return on orchard investment and greater profitability over the life of the orchard. There are other obvious reasons that have driven growers to these planting systems, including lack of skilled labor and the use of growing and harvesting aids and bulk handling equipment.
Fifty years ago, there were many apple orchards planted with standard seedling rootstocks and some semi-standard Malling and Malling Merton rootstocks. Through education by Extension and research specialists, nurserymen and progressive growers, we all learned the benefits of using these rootstocks to plant closer, and more easily and profitably managed, orchard systems.
The International Dwarf Fruit Tree Association was organized in the late ’50s, and did a tremendous job assembling people to hear about and see successful intensive orchard plantings. Smaller trees on MARK, Malling, Polish and Budagovsky varieties and clones of rootstocks became more popular as we moved to closer spacings and smaller trees. Today, we are planting new Cornell Geneva stocks better adapted to our climate, as well as Pajam and Supporter. A systems approach to pruning and training has maximized the efficiency of today’s apple varieties and rootstocks.
We have also seen some dramatic changes and increased intensive plantings in sweet cherries, with the propagation and planting of sweet cherry varieties on Gisela rootstocks. These have made major changes in Eastern U.S. cherry orchards, which frequently are marketed u-pick. Use of these dwarfing combinations has enabled us to grow smaller cherry trees, which are easier to harvest under plastic tunnels and other coverings – thus avoiding damage from birds and rain.
Intensive pear plantings have been around for 50 years, first centered in California and southern Oregon. More intensive orchard systems were developed on seedling stock, but more efficiently on Quince and, more recently, the Old Home Farmingdale stocks.
The intensification of peach orchard systems was less dramatic until recently. Most trees for the past 50 years have been planted on seedling rootstocks of Tennessee Natural, Lovell, Nemaguard, Halford and, more recently, Guardian. These rootstocks have produced vigorous trees more challenging to manage in intensive orchards systems.
We are still learning to manage them, particularly as orchards age. New dwarfing rootstock from California may enable us to see more intensive peach orchard plantings.
Kevin Day, University of California: For more than 100 years, the open vase has been the most popular training system used in California. Initial spacings were commonly 22 feet by 22 feet to accommodate the cross-cultivation required to control weeds. As herbicides were introduced in the 1950s and ’60s, growers were able to eliminate cross-cultivation and spacing distances could be decreased.
Since then, growers and researchers have worked with a number of systems, many of which were not amenable to their situation. California’s long growing season and high vigor conditions require systems that make light management simple and relatively inexpensive. Consequently, the primary tree form is still open vase, with spacings of 16 x 18 and 18 x 18 most common.
High labor costs are forcing growers to examine all areas of their operations, and there is great interest in reducing reliance upon ladders. Orchard heights have decreased and most trees are now 11-12 feet high, rather than the 13-14 feet common a decade ago. There is also great interest in semi-dwarfing rootstocks, but no commercial orchards of consequence have yet been planted.
Growers also need to increase returns as quickly as possible, and moderate-density plantings are becoming more popular. These plantings are usually trained to the 4-leader Quad-V and 6-leader Hex-V forms. These systems are usually spaced at 8-10 x 18 and 12 x 18, respectively. Some growers are also planting these systems at 15-16-foot row spacings, with the intent of keeping ultimate tree height at 9-10 feet or less.
These systems are popular for several reasons, including moderate density – which keeps tree costs low – and excellent light penetration throughout the canopy, since the centers of the tree are kept open. These two systems also provide the great benefit of “regimentation,” with every tree in the orchard being virtually identical to the others in terms of form and scaffold/branch number. This simplifies pruning and makes it easier for workers to train and establish the orchards since, depending on the system in use, either four or six scaffolds are left – never more, never less.
Regimentation also helps assist in crop-load regulation, making management during pruning and at thinning easier. Using a Quad-V orchard as an example, if the desired fruit count is 400 fruit per tree, then 100 fruit are needed on each scaffold. If four fruit are typically left on each shoot at thinning, then 25 fruiting shoots per scaffold are required at pruning.
Greg Reighard, Clemson University: In the 1980s, peach trees were still being planted at 20 feet by 24 feet (91 trees/acre) with 20 x 20 (109 trees/acre) being a tighter spacing. This does not include the drive rows, which are every six rows and wider for the bin trailers, etc. Almost all trees were trained as an open-center form, with tree height kept below 8-10 feet. All trees were budded on peach seedling rootstocks.
In the 1990s, tree spacing for the open-center form graduated down to 18 x 18 (134 trees/acre), 16 x 18 (151 trees/acre) and even 14 x 18 (173 trees/acre), excluding the wider drive rows. These tighter-spaced trees were also supported with twine/cord banded around the outside of the scaffolds to support the crop. Tree height tended to go up to 10 feet or higher for some varieties.
During this same period, the Kearney Perpendicular-V and Quad-V training systems were tried by several growers, partly because a new peach rootstock (Guardian) was released that survived much better; thus growers were more willing to plant trees at denser spacings. These systems were planted at 6 x 18 (V) and 9-10 x 18 (Quad-V) spacings. Due to tractor size, 16-foot spacings between rows were often not used. Tree heights in these high-density systems usually reached 16 feet during the growing season, and required cross-row tying to prevent excessive lean from the prevailing winds.
Also, the scaffolds were banded/roped/corded to help support the crop and prevent splitting in the scaffold crotch. No permanent trellising was used. During this time, no viable semi- or dwarfing peach rootstocks were available, so vigor control relied on pruning techniques.
In the past 10 years, the vast majority of trees are still trained as open-center forms, but now a tight vase system is being used more often. Tree spacings of 14 x 18 are not so rare, and scaffolds are kept smaller. The V and Quad-V systems are still being used, but make up less than 10 percent of the acreage. The rootstock is still primarily Guardian, a vigorous peach seedling, so tree spacing will not decrease until semi-dwarfing or dwarfing rootstocks are released that do not runt the tree and are tolerant to peach tree short life syndrome and Armillaria root rot.
Due to the industry’s reliance on peach seedling rootstocks and available migrant labor, the open-center tree form will continue to be used in South Carolina in this decade, like it has been for 100-plus years, but with closer-spaced trees than in the past.
By Matt Milkovich