A Detailed Explanation of Shaping and Pruning Methods and Key Technical Points
Whether saplings or bouquets, once they have grown to a certain extent, they must be pruned to improve their ornamental value and growth vigor. So what are the shaping and pruning methods?
1. Thinning
Refers to cutting branches off from the base.
Thinning can remove diseased and pest-infested branches, dead and dry branches, useless water sprouts, overly dense crossing branches, and branches that conflict with municipal facilities. Thinning can improve ventilation and light conditions, enhance leaf photosynthetic efficiency, increase nutrient accumulation, and benefit growth and flower bud differentiation. Thinning weakens the overall growth vigor of the whole tree; the growth vigor of branches above the wound is relatively weakened, but the growth vigor of branches below the wound is relatively enhanced. This is the so-called “suppress the top and promote the bottom” effect.
Removing large branches should be carried out gradually over several years, otherwise there will be too many wounds, which will weaken the tree's vigor. When thinning branches, master the principle of cutting from the base, leaving no stub, and keeping the wound surface as small as possible.
In gardens, after hedges and spherical trees are pruned by heading back, branches will become densely grown, and there will be too many dead branches and bare branches inside the canopy, so it must be combined with thinning.
2. Heading back
Refers to the pruning method of removing a portion of a one-year-old branch.
Heading back can stimulate the lateral buds below the cut to sprout. According to the degree of severity, it is divided into:
(1) Light heading back. That is, cutting off a portion of the top of a one-year-old branch (i.e., 1/5 to 1/4). Mostly used for pruning strong branches of flowering and fruiting trees. Light heading back stimulates most of the semi-plump buds below the cut to sprout, forming many medium and short branches.
(2) Medium heading back. That is, cutting at the plump buds in the middle or upper-middle part of the branch. After cutting, many medium and long branches are formed, with high branching ability, which is beneficial to growth and expanding the canopy. Generally mostly used for cultivating scaffold branches, large branch groups, and extension branches, etc.
(3) Heavy heading back. Cutting off most of the branch (cutting off 2/3 to 3/4 of the total length of the branch). In this way, the original branch retains few buds, nutrients are concentrated, and 1 to 2 vigorous branches can sprout below the cut. This method is mostly used for renewing aging trees and rejuvenating weak branches.
(4) Extremely heavy heading back. Cutting back leaving 1 to 2 shrunken buds at the base of the branch. Generally only 2 to 3 short branches or thin weak branches sprout, which can lower the branch position. This method is used for trees in order to ease growth vigor.
3. Auxiliary pruning
(1) Renewal pruning. That is, cutting a perennial branch back to a branching point, which can lower the position of apical dominance and promote renewal and rejuvenation of the perennial base.
(2) Pinching. A technical measure of cutting off the tender tip of new shoots during the growing season (e.g., pinching wintersweet (Chimonanthus praecox) during summer growth can promote nutrient accumulation and more flowering in winter).
(3) Tip pruning. During the growing season, cutting off the tip of generally lignified new shoots of overly vigorous branches, mainly to adjust the relationship between the main branches and lateral branches of the tree.
(4) Notching. Making a horizontal cut with a knife near a bud down to the xylem of the branch. The wound length is 1/3 of the branch circumference. This method can block nutrient supply and stimulate the lower buds to grow.
(5) Bud removal. Cutting off useless buds or buds that hinder the growth of the main trunk and branches. Such as: root suckers of Chinese rose (Rosa chinensis), tree peony (Paeonia suffruticosa), and flowering pomegranate (Punica granatum), etc.