Training young free-standing apple trees

 Article written by Madeline Wimmer, UMN Extension Fruit Production Educator.  

Images: Bramley Seedling (England 1809) apple variety being trained, initially using a heading cut during dormancy to promote shoot growth, followed by shoot manipulation done this week (left image). Clothespins and similar products come in various sizes and the trunk diameter should in part determine which ones are used (right image). Image taken at The Garden Lab located in Rochester, Minnesota (Zone 5a).   

Apple tree height and the number of years to fruiting (precocity) depend largely on the rootstock an apple variety is grafted onto. Establishment is the process of caring for a tree after planting to maintain its health, while training relates to encouraging a specific tree shape for the benefit of its health and production. This article goes into concepts of pruning and branch manipulation for free-standing tree establishment. While pruning is done during the dormant season, it is being discussed in this article because it is important for tree establishment. 

Pruning influence on tree training

Previously, UMN Extension delivered a talk on pruning free-standing apple trees, which covered information on training apple trees through dormant pruning techniques. Pruning goals for training include removing forked leaders, removing or cutting back laterals that are competing with the leader, as well as removing early lateral branching from scaffolds. In general, pruning to increase sunlight is also a priority, which leads to high productivity by supporting fruit spur development within the tree canopy. The most basic concepts for pruning techniques include thinning cuts done to remove a branch and discourage regrowth, and heading cuts that encourage shoot growth near the location of the pruning cut. 

Image: David Bedford, UMN Fruit Breeder, demonstrates a heading cut on a young apple tree to promote branching below the cut point at the UMN Horticultural Research Center.

A heading cut is simply one that cuts back a branch when a tree is dormant, whereas full removal would be a thinning cut. Heading cuts have been traditionally used on the leader to establish standard and semi-dwarf apple trees (ex M.7, G.890) when planted as bare root whips for central-leader training systems, but they can also be used for other systems like espalier. This promotes branching for the first scaffold branch layer. It can also be used on very young trees that have large sections on blind wood on trunks. Heading cuts generally promote growth about 12–24 inches below the cut. 

Heading cuts happen during pruning, but the next step, promoting lateral growth and wider branch crotch angles can occur during the growing season. This practice is sometimes called branch manipulation, as wider branch crotch angles lead to stronger branches and reduces the branch vigor, as compared to branches with narrow crotch angles. 

Branch manipulation techniques for training

Branches are malleable during the first couple of growing seasons, and benefit from techniques that pull down branches with weight, spreaders, or staking. One method of spreading branches can be done with young shoot growth (see above image). This technique can be done using clothespins at the right time and is fast and simple. During this time of the growing season, shoots are still malleable, which is good timing for the process, but care should be given when growth is still tender to avoid breaking shoots. To be successful, growers should also find supplies that are suitable for the trunk diameter of trees that require training. 

Image: Liz Griffith of Door Creek Orchard holds a few tree limb spreaders for small diameter branches.

Tree limb spreaders are the next option for branch manipulation, which work well on current season shoots that are becoming woody (lignifying), one-year-old branches, and some two-year-old branches if they are flexible. Tree limb spreaders are placed between branches and will push the lower branch into a wider angle. 

Note on high density production

Apple trees that are grafted onto rootstocks with a stronger dwarfing potential (ex B.9, G.11) still benefit from pruning forked leaders and limbs with diameters that compete with the leader; however, there’s less requirement for branch manipulation. The trees themselves will fruit much sooner, while branches are younger and malleable, which will weigh the branches down automatically. There are even cases when young apple trees bear too much, too soon, which can lead to branch injury, breakage, or an excessively drooping branch.  

Resources:

Rootstocks for apple (Washington State University)

Geneva apple rootstock comparison chart (Cornell University; e.g., G.41, G.935)

Training and pruning apple trees (University of Wisconsin; information and diagrams demonstrating branch manipulation)