Detailed Explanation of Key Points of Winter Pruning Techniques for Cornus officinalis

Cornus officinalis, also known as zaopi, yaopi, and yurou, is a traditionally precious woody Chinese medicinal material in our country, with extremely wide medicinal uses. Foping County, Shaanxi Province, has a long history of cultivation and has already formed large-scale production. In 2001 and 2002, the county was respectively named “China's Hometown of Cornus officinalis” and “National-Level Cornus officinalis Medicinal Source Base County” by the State Forestry Administration and the Ministry of Science and Technology. Moreover, Cornus officinalis has become an important component of ecological construction in Foping County and is a pillar industry of the local rural economy. The author has been engaged in Cornus officinalis production in Foping County for more than 30 years and has accumulated and summarized a relatively mature set of planting experience. The deep winter pruning techniques are now introduced for the reference of the broad community of medicinal herb growers.

In winter, Cornus officinalis enters dormancy. Deep winter pruning can prevent sap loss, ensure its safe overwintering and robust growth the following year, and more importantly, change the tree shape and regulate nutrition, transforming it from planar fruiting to three-dimensional fruiting, thereby achieving the goal of increasing per-unit yield and total output.

Pruning Methods for Cornus officinalis

1. Thinning, also called thinning branches. Its role is to promote the sprouting and growth of branches below the cut, moderate tree vigor, and it is mostly used where branches are too dense by cutting the first branch from the base, which can improve light conditions, extend the life of fruiting branches, promote flower bud formation, and increase fruit set rate. Removing strong vigorous branches promotes growth to balance tree vigor; removing weak branches can promote the growth of other branches.

2. Heading back, cutting off a portion of the treetop, also called short pruning. Its role is to promote new branch sprouting from buds below the cut, rejuvenate old branches, and promote flowering and fruiting.

3. Renewal pruning, that is, heading back on perennial branches, used to control auxiliary nurturing branches, cultivate fruiting branch groups, and promote the renewal and rejuvenation of scaffold branches.

4. Leaving unpruned, also called long release. That is, retaining branches without pruning. Generally, only relatively weak branches, lower-tier branches, and the like can be left unpruned. Its roles are, first, to moderate growth vigor: for vigorous trees and vigorous branches, it can moderate growth vigor; for weak trees and weak branches, under conditions of strengthened water and fertilizer, it can restore growth as quickly as possible and strengthen tree vigor. Second, it is beneficial for flowering and fruiting: Cornus officinalis has the characteristic of flowering and fruiting from axillary buds, and leaving vegetative branches unpruned can promote more flowering and more fruiting.

Pruning and Training for High-Yield Tree Forms

1. Open-center tiered form: also called scaffold-branch tiered form. The trunk height is 60-80 cm, and the scaffold branches are arranged in sparse tiers on the central leader. The first tier retains 3 scaffold branches, arranged close together, 30-40 cm apart, with an opening angle of 50°-60°; the second tier retains 2 scaffold branches, arranged in the spaces of the first-tier scaffold branches; the third, fourth, and fifth tiers each retain one scaffold branch, with the top removed to open the center. Distance between tiers: 80-100 cm between the first and second tiers, 60-70 cm between the second and third tiers, arranged in a staggered manner. Its characteristics are a full tree crown, a firm framework structure, reasonable distribution of scaffold branches, open angles, and good ventilation and light penetration; fruiting branch groups are borne on scaffold branches and lateral branches, and the fruiting area is large, overcoming the shortcomings of excessive branches and trunks and a closed canopy under natural growth conditions. This tree form is suitable for scattered planting around houses and in front of and behind them, as well as for shaping and pruning Cornus officinalis trees with deep soil layers and vigorous growth.

2. Natural open-center form: also called open-center form without a central leader. There are 2-3 scaffold branches, 40-60 cm high, growing outward at a slant, at 45°, with an azimuth angle of 120°. On each scaffold branch, more than 4 secondary scaffold branches are retained: the first secondary scaffold branch is retained on the outer side of the scaffold branch, and the second, third, and fourth secondary scaffold branches are arranged in order on the outer side of the scaffold branch, with a branch spacing of about 35 cm. On these, developmental branches are retained as inverted branches to cultivate fruiting branch groups. This tree form is relatively short, with an open crown, good ventilation and light penetration, and convenient management, and is suitable for pruning and shaping Cornus officinalis trees on hillside land with shallower soil layers and barren soil.