Ferree and Schupp (2003) described two kinds of pruning cuts. Thinning cuts, whereby the limb is entirely removed, limit the possibility of regrowth by excision of all axillary buds and thin the canopy. With heading cuts, a portion of the limb is retained and the attendant axillary buds allow release from apical dominance, resulting in localized stimulation of branching.
Stubbing is a type of heading cut whereby only a small section of a 2-year-old or older limb is retained to limit the potential branching to a few latent axillary buds near the origin of the limb. Short stub cuts are recommended for spindle-type apple tree training to stimulate the regrowth of new lateral branches, to restrict the canopy volume and branching density, and to maintain favorable distribution of sunlight throughout the canopy (Oberhoffer, 1990; Robinson, 2003; Wertheim, 1968). Stubbing, or renewal pruning, is also beneficial for reducing the fruiting capacity of apple and is an important step in crop load management (Kon et al., 2018; Schupp et al., 2017).
Wertheim (1968) recommended that limbs should be removed, thus leaving a stub with an upward-facing bevel to stimulate a shorter, weaker wide-angle branch to develop from the lower side of the stub (Fig. 1). In most cases, such a wide-angle branch tends to be more fruitful and is preferred to an upright branch with more vigorous vegetative growth. This beveled stub cut, often referred as a “Dutch cut” (Ferree and Schupp, 2003) in recognition of the early development of spindle training and pruning systems in The Netherlands, has often been recommended for spindle-style trees (Crassweller et al., 2005; Robinson, 2003; Schupp, 2013). To our knowledge, there has never been a study of stub angle or length that has shown that a short stub with an upward-facing bevel is the optimal technique for obtaining new fruiting lateral branches with a more horizontal branch angle and low vigor.
This study evaluated short bevel cuts for limb renewal and the effects of renewal cuts at three angles and two stub lengths on renewal shoot number, position, angle, and length of dormant pruned apple trees.
CrasswellerR.SchuppJ.BaugherT.2005Cookbook guidelines for apple training systems. 27 Nov. 2018. <https://extension.psu.edu/apple-training-systems-cookbook-guidelines>
FerreeD.C.SchuppJ.R.2003Pruning and training physiology p. 319–344. In: D.C. Ferree and I.J. Warrington (eds.). Apples: Botany production and uses. CABI Wallingford UK
HerrickC.2017Pruning goes high-tech. Amer. Fruit Grower 2017(June):6–7
KonT.M.SchuppJ.R.YoderK.S.CombsL.D.SchuppM.A.2018Comparison of chemical blossom thinners using ‘Golden Delicious’ and ‘Gala’ pollen tube growth models as timing aidsHortScience5311431151
OberhofferH.1990Pruning the slender spindle. Province British Columbia Ministry of Agriculture Fisheries Victoria BC Canada
RobinsonT.L.2003Apple-orchard planting systems. p. 345–407. In: D.C. Ferree and I.J. Warrington (eds.). Apples: Botany production and uses. CABI Wallingford UK
SchuppJ.R.2013Renewal pruning for high density apple plantings. 27 Nov. 2018. <http://extension.psu.edu/plants/tree-fruit/news/2013/renewal-pruning-for-high-density-apple-plantings>
SchuppJ.R.WinzelerH.E.KonT.M.MariniR.P.BaugherT.A.KimeL.F.SchuppM.A.2017A method for quantifying whole-tree pruning severity in mature tall spindle apple plantings. HortScience 52:1233–1240
WertheimS.J.1968The training of the slender spindle. Pub. No. 7. Proefstation Voor De Fruiteelt Wilhelminadorp The Netherlands