Yes, you can prune mulberry trees in summer, but this practice differs fundamentally from the heavy structural cuts performed during winter dormancy. The mulberry tree (Morus spp.) is a fast-growing deciduous species whose vigorous growth often necessitates regular pruning to control its size and shape. While dormant pruning establishes the tree’s scaffold, summer pruning is a maintenance activity involving lighter cuts to manage active growth and direct energy away from excessive height and spread.
The Primary Goal of Summer Pruning
The main objective of summer pruning is to suppress vegetative growth and manage the tree’s size, a major concern due to the mulberry’s rapid growth rate. Removing actively photosynthesizing leaves and new shoots reduces the tree’s capacity to produce and store carbohydrates. This mechanism limits the energy the tree dedicates to continued growth, effectively slowing its expansion.
Growth suppression is valuable for keeping large mulberry trees manageable in a home landscape, easing fruit harvesting, and maintaining an ornamental form. Summer pruning also aids fruit management, particularly on fruiting varieties. Removing growth after the initial fruit harvest can sometimes stimulate a second, smaller crop later in the season, depending on the cultivar.
Thinning the canopy slightly allows better light penetration and air circulation to the inner branches, which helps ripen remaining fruit and reduces the risk of humidity-related fungal issues. The reduction in carbohydrate production following summer pruning limits the tree’s overall vigor and helps keep its size in check for the following year.
Distinguishing Summer Pruning Techniques
Summer pruning focuses on the selective removal of new growth rather than major structural alteration. The preferred method for reducing size while maintaining the tree’s natural form is the use of ‘thinning cuts.’ This technique involves removing an entire branch or shoot back to its point of origin, such as a main branch, the trunk, or a lateral branch.
Thinning cuts are preferred over ‘heading cuts,’ which involve cutting a branch back to an arbitrary point or bud. Thinning cuts reduce the canopy volume without stimulating dense, bushy regrowth. Heading cuts often lead to a proliferation of weak, upright shoots that make the tree look more overgrown.
Summer pruning is also the ideal time to manage common issues like suckers and waterspouts, which vigorously emerge during the active growing period. Suckers grow from the roots or trunk base, while waterspouts are fast-growing, vertical shoots on main branches, and both should be removed completely. To prevent the entry of disease during warm, moist summer months, use clean and sharp tools to ensure precise cuts that heal quickly.
Timing and Severity: When to Prune and How Much
The window for summer pruning is generally after the tree’s first major growth flush and the initial fruit harvest, typically between late spring and early summer. Pruning at this time maximizes the growth-suppressing effect by removing actively feeding foliage. Complete all summer pruning activities well before late summer or early fall.
Pruning too late encourages a flush of tender new growth that will not have time to harden off before the first frost. This soft wood is highly susceptible to winter damage, which can severely stress or injure the tree. Therefore, the severity of summer pruning must be carefully limited.
A foundational rule is never to remove more than 20 to 25% of the tree’s entire leaf canopy in a single season. Exceeding this limit causes significant stress, forcing the tree to expend stored energy on wound repair and regrowth. Excessive canopy removal also exposes the underlying bark to direct, intense sunlight. This exposure can cause sunscald on the newly exposed, thin bark, potentially leading to permanent damage.