CENTRE HALL — To prune or not to prune is a continuing dilemma that gardening enthusiasts from professionals to home gardeners have to deal with every growing season.
From trees to shrubs, the why, when and how of pruning are among the most difficult aspects of horticulture to understand.
The problems spring from the fact that pruning is risky. It essentially is deliberately damaging a plant in order to make it healthier, more productive or more aesthetically pleasing. And it’s because of that damage that many casual gardeners pause to consider exactly how to proceed — or they call a professional.
Fortunately, there is help out there, and one form of it took place when the Rhoneymeade Arboretum and Sculpture Garden sponsored a workshop on the theory and principles of fruit tree pruning on March 10 in Centre Hall.
The workshop was conducted by Bob Hricko, a Penn State graduate and plant scientist who now helps manage his family’s fruit farm in Elysburg. Hricko specializes in the care and maintenance of the farms’ many acres of fruit trees, and the workshop concentrated on how he uses a knowledge of tree physiology to help insure successful pruning.
“I am now working on my grandparents’ orchard,” Hricko said, “and we have about 100 acres of mixed fruit trees, mostly apples, but also others like nectarines and cherries.
“My goal today is to give a theoretical background on tree physiology and how trees grow and then to take that and apply that to pruning techniques.”
Hricko began the workshop by discussing the goals of pruning and then moved to the types of pruning cuts, the physiology of trees — he used mostly apple trees as examples — and the approaches to different types of tree structures.
“There are so many different ways to prune,” he said, “that the best way to do it in your particular situation is to understand the principles behind it and then make decisions based on what you want to do with your trees on your land.”
According to Hricko, the goals of pruning are to:
■ Remove disease incidence and or potential
■ Let light into the tree
■ Allow the canopy to dry and have air flow
■ Keep trees small and easy to work on (especially in an orchard environment)
■ Encourage new growth
“Cutting out dead or diseased limbs makes spreading of disease much less likely,” Hricko said, “and light is essential for energy capture, fruit size, fruit coloring and uniform canopy density.”
He also added that pruning is a “dwarfing process” and that tree size is reduced, but “cutting back old growth stimulates new growth.”
Next, the discussion moved to the types of pruning cuts.
First, there is a heading cut in which a branch is cut off partway. Then, there is a thinning cut where a branch is “cut all the way back to the to the trunk or parent branch.”
Essentially, according to Hricko, thinning cuts are used to open up trees and maximize the light available to grow fruit or vegetation. The proportion of each type of growth depends on many factors (age, weather, vigor, etc.), but “good pruning shows growth to a manageable rate and frees up energy for fruit.”
Out in the Rhoneymeade orchard, Hricko demonstrated on one of the apple trees how thinning cuts remove less productive limbs and allow light and air to reach other, potentially more viable limbs.
Heading cuts depend on what Hricko described as “apical dominance.”
“This is what keeps all branches from growing to the same length,” he said. “The tip of the shoot produces a hormone and sends it to the lower, lateral branches, which keeps them from competing. Heading cuts interrupt this process and lead to a mass of equal-length shoots. Maintaining a strong leader promotes this process.”
In the orchard, Hricko demonstrated how heading cuts could leave a strong leader that would eventually promote better fruit growth and even direct branches into open areas of the tree.
Hricko did add cautions about the pruning processes, however. Wounding decreases cold hardiness, he said, and it’s best to avoid it two weeks prior to any particularly cold weather.
There was also some discussion about the possibility of introducing disease, possibly through the pruning tools, but otherwise healthy trees should not have a problem, he said.
Overall, the pruning process can have very beneficial results, especially if the goals are clear and the types of cuts are well considered.
More information on Rhoneymeade, its programs, workshops and trips can be found at www. rhoneymeade.org.
