Pruning Methods for Neglected Walnut Trees in Production Areas

  In China's walnut production areas, many trees are managed extensively, harvested but not tended, rarely pruned, and left to grow naturally, becoming neglected trees.

  1. Structural characteristics of neglected trees The general characteristics of such trees are numerous scaffold branches, disordered tree shape, bare inner canopy, dead small branches, poor ventilation and light penetration, fruiting sites severely shifted outward, strong upper growth and weak lower growth, and unclear tiering.

  2. Pruning methods

  (1) Shape the tree according to the tree, prune according to the tree, and handle flexibly. For trees taller than 5 m, first open the skylight and lower the head level by level, noting that there must be a follower branch below the pruning or saw cut. For trees with too many large branches and a bare rear portion, select 5-7 large branches with good orientation, appropriate spacing, and vigorous growth as scaffold branches, while the remaining large branches should be heavily renewal-pruned or removed, but do not act too hastily; handle them by year and in batches to avoid creating too many large wounds and weakening tree vigor. If the central leader is obvious, it can be transformed and trained into a modified leader form; otherwise, train it into a natural open-center form, avoiding excessive insistence on tree shape and heavy cutting and sawing, which affects yield. For small trees with a leaning trunk, the trunk must be straightened; after the trunk becomes crooked, the upward scaffold branches grow vigorously, while the branches behind often grow weaker, causing unbalanced growth among the basal scaffold branches. For vigorous branches, open the angle wide, or appropriately renewal-prune to control vigor and maintain a coordinated relationship among the scaffold branches.

  (2) Analyze large branches, adjust reasonably, and determine which to keep or remove. The large branches of neglected trees are crowded and dense; excess scaffold branches can be renewal-pruned and transformed, treated as side branches of adjacent scaffold branches to fill gaps. Trees growing on trees should be promptly renewal-pruned or removed; when there is space, they can be pulled flat and transformed into side branches or branch groups.

  (3) Treatment of peripheral branches. Peripheral branches with scorched tips can be appropriately renewal-pruned back to a point where there is branching on a large branch, to promote new shoots in the inner canopy and restore tree vigor. Weak drooping branches and dead branches can all be removed to promote vegetative growth.

  (4) Training and renewal of fruiting branch groups. In transformed trees, water sprouts often emerge in the inner canopy and must be promptly transformed into fruiting branch groups. For overly long branch groups, cut back at the perennial portion, retaining strong branches and strong buds to renew the branch group and fill out the canopy. The training of fruiting branch groups should combine large, medium, and small ones.