The grafted weeping willow, often a cultivar like Salix babylonica or a similar weeping variety, is a highly prized ornamental tree known for its dramatically cascading branches. This distinctive form is created by joining two different willow species together. The weeping portion, known as the scion, is fused onto the trunk of a non-weeping, more robust rootstock. Proper pruning is necessary to maintain the tree’s health, structural integrity, and the signature weeping appearance.
Addressing Suckers and Growth Below the Graft Point
The unique structure of a grafted weeping willow requires focused attention on the graft union, which is the slightly swollen area where the weeping top meets the straight trunk. The most significant pruning task is the immediate removal of any growth emerging from the trunk below this graft union. These growths are known as suckers, and they originate from the rootstock, which is the non-weeping variety.
Suckers possess the aggressive growth habits of the rootstock. If left to grow, they will quickly out-compete the desirable weeping scion for water and nutrients. This aggressive growth will eventually take over the tree, causing it to revert to the non-weeping form of the rootstock, destroying the ornamental value. Suckers should be removed as soon as they appear, regardless of the season, to prevent this reversion.
To remove suckers, trace the growth back to its origin on the trunk and cut it off completely. Make a clean, flush cut right where it meets the main stem. Never leave a stub, as this will only encourage multiple, even more vigorous suckers to sprout from the same point.
Vigorous, upright shoots that emerge directly from the main weeping branches above the graft are called water sprouts. Water sprouts are distinct from suckers due to their straight, vertical growth pattern, contrasting with the pendulous weeping branches. While they do not threaten to revert the tree like suckers, their upright habit ruins the desired aesthetic. They should be thinned out to maintain the graceful, flowing silhouette of the canopy. This vigilant removal of both suckers and water sprouts is necessary for preserving the tree’s grafted identity.
Optimal Timing and Necessary Equipment
The optimal time for major structural pruning of a weeping willow is during its dormant season, typically in late winter or very early spring before new leaves emerge. Pruning during this period minimizes stress on the tree and allows for a clear view of the branch structure without foliage obstruction. Willows are known to “bleed” sap heavily if pruned during active growth, and this excessive sap flow can attract pests and create a messy, sticky situation.
If the weeping willow is a variety that produces ornamental catkins in the spring, a light pruning can be done immediately after the catkins fade. However, the dormant season remains the safest time for making larger cuts or performing significant canopy reduction. Removing dead or diseased wood is an exception and should be done immediately, regardless of the time of year, to prevent pathogen spread.
Effective pruning requires sharp, clean tools to ensure precise cuts that heal quickly and minimize damage to the bark. For small, thin branches, sharp bypass hand pruners are the appropriate tool. Medium-sized branches require loppers, which provide greater leverage for cuts up to about two inches in diameter. For thicker, higher branches, a pruning saw or a pole pruner may be necessary to ensure safety and accuracy.
Before starting work, all cutting surfaces must be sanitized, typically with a solution of rubbing alcohol or a diluted bleach mixture. This prevents the transmission of plant diseases between cuts or trees. Using dull tools will crush the wood fibers, creating a jagged wound that heals slowly and leaves the tree vulnerable to pests and disease. Maintaining sharp, sterilized equipment is important for the health of the tree.
Technique for Shaping the Weeping Canopy
Canopy shaping focuses on the weeping branches above the graft union, aiming to enhance the tree’s health and aesthetic appeal. This process involves three primary types of cuts: thinning, heading back, and deadwood removal.
Thinning
Thinning is the removal of an entire branch back to its point of origin on a larger limb or the main trunk, which helps to increase air circulation within the canopy. Improved air flow reduces the humid conditions that favor the development of fungal diseases, which willows are susceptible to. When thinning, focus on removing branches that are crossing, rubbing against each other, or growing inwards toward the center of the crown. This opens up the tree and allows light to penetrate the inner structure, encouraging more vigorous growth.
Heading Back
Heading back involves shortening the length of the weeping branches to maintain a desired clearance from the ground or to increase canopy density. When heading back a branch, the cut should be made just above an outward-facing bud or a lateral side branch. Making the cut at a slight angle approximately one-quarter inch above a bud directs the new growth outward, preserving the graceful weeping form.
It is recommended to remove no more than 25 to 30 percent of the tree’s total living canopy in a single season to prevent excessive stress. Over-pruning can stimulate a flush of weak, vertical growth, which detracts from the weeping habit. Long, trailing branches that touch the ground can be cut back by about one-third of their length to lift the canopy and prevent breakage or damage from lawn maintenance.
Deadwood Removal
Dead, damaged, or diseased wood should be removed completely, cutting back into healthy tissue. Dead branches are brittle, lack buds, and can harbor pests or pathogens, necessitating their immediate removal.
When removing a large branch, use the three-cut method to prevent the bark from tearing down the trunk. The first cut is an undercut about a foot from the main trunk. The second cut is a top cut a few inches beyond the undercut to drop the weight. The third cut is a final cut to remove the stub just outside the branch collar.