Timing is Everything: Determining the Best Season to Prune Mulberry Trees

Mulberry trees are beloved for their sweet, flavorful berries and valued for their lush, spreading shade. But left unpruned, their vigorous growth can quickly get out of hand. Knowing when to strategically trim mulberry trees is key to keeping them healthy, productive and structurally sound. Read on to learn about the factors that determine the optimal timing for mulberry tree pruning.

Why Prune Mulberry Trees?

Before delving into when to prune, let’s review the reasons for pruning in the first place:

• Control size and shape
• Remove dead or damaged branches
• Improve air circulation and light penetration
• Encourage fruit production
• Facilitate harvesting
• Maintain structural integrity

Implementing timely pruning helps achieve these important objectives. Neglecting to prune regularly often results in poor tree structure, reduced yields and safety hazards.

Key Principles for Pruning Mulberries

Adhering to some basic principles is also important when pruning any tree

• Always use clean, sharp tools to maximize cutting efficiency and minimize injury risk.

• Cut just outside the branch collar without leaving stubs

• Favor removal of entire branches over heading cuts when possible.

• Never remove more than one-quarter of the tree canopy in one season.

• Disinfect tools between cuts to avoid spreading disease.

These guidelines help ensure proper pruning technique to optimize tree health.

Spring Pruning of Mulberry Trees

Spring, just before buds begin to swell and leaf out, is generally the optimal time for pruning mulberry trees. The reasons why spring wins out as the prime season include:

Enhanced Recovery

• Cuts seal more rapidly due to active sap flow.
• New foliage soon develops to replace removed wood.
• Trees are establishing energy reserves to support growth.

Better Branch Visibility

• Lack of leaves reveals branch structure for selective pruning.
• The impact of cuts is easily assessed.
• Dead or damaged wood is readily identified.

Avoidance of Sap Bleeding

• Bleeding from pruning wounds is minimized in spring.
• Sugar content and pressure in sap is lower than during winter.
• Oozing sap attracts insects and pathogens.

Prevented Pest/Disease Spread

• Spring growth has not yet emerged to catch and disperse pathogens.
• Danger of embedded fungi and insects spreading is reduced.

Minimal Stress

• Cool temperatures preclude heat stress during recovery.
• Adequate soil moisture prevents added drought stress.

Appropriate Timing vs. Fruiting

• Pruning is completed just before flowering and fruit set.
• Removal of some new growth won’t significantly reduce yields.

For all these reasons, pruning just as the mulberry tree awakens from winter dormancy is generally the best option.

Pruning Mulberry Trees in Summer

Pruning mulberry trees in summer is not advisable for several reasons:

• Hot temperatures increase stress during recuperation.
• Active foliar growth is removed, slowing food production.
• Sap flow is maximal, increasing risk of bleeding from cuts.
• Bees may still be pollinating flowers and forming fruit.

However, summer pruning may be warranted to:

• Eliminate broken or hazardous branches for safety.
• Improve air circulation and light levels on crowded interior branches.
• Selectively remove water sprouts competing with stronger scaffolds.

Just use restraint, pruning only as needed rather than shearing trees heavily. Avoid pruning mulberries after mid-summer to allow sufficient recovery time before winter. Monitor for sun scalding effects after summer cuts remove shading foliage.

The Case Against Pruning Mulberry Trees in Winter

Though visually optimal for seeing branches, pruning mulberry trees in winter is ill-advised:

• Cuts are slower to seal due to dormant sap flow, leaving wounds vulnerable to pathogens and insects.

• Exposure to harsh winter elements hampers recovery.

• Chilling inhibits growth of wound-sealing callus tissue.

• Dormant trees have lower energy reserves to fuel regrowth.

• Cold temperatures exacerbate “bleeding” of sap from cuts.

• Dieback and browning of new shoots may occur after pruning during winter dormancy.

For these reasons, limit winter pruning to elimination of definite hazards or dead wood.

Special Case – Pruning Young Trees

Pruning objectives differ for newly planted trees compared to mature specimens, thus optimal timing shifts. For young mulberry trees:

• Prune in early spring only after plant has broken dormancy.

• Remove crossing, damaged or poorly attached branches.

• Establish basic scaffold structure and spacing.

• Limit removal of first-year growth until tree is established.

• Monitor sunburn potential on thin bark after pruning.

The goal is to train desirable permanent branching while supporting healthy establishment. Delay major corrective pruning on young trees until they mature.

Putting it All Together – Ideal Pruning Calendar

Considering seasonal factors and growth habits, here are general guidelines for scheduling mulberry tree pruning:

• Spring – The prime time to prune mulberries. Thin and shape established trees before buds swell. Also train young trees.

• Summer – Limit to removal of hazards, water sprouts and interior shaded branches.

• Fall – Second choice for pruning if needed to control mature tree size. Should be completed by early autumn.

• Winter – Only prune if essential to eliminate hazards or dead wood.

Of course, unexpected issues like storm damage may require pruning at less optimal times. But adhering to this seasonal calendar as much as possible will maintain healthy, productive mulberry trees.

Executing Proper Pruning Cuts

Once the timing is right, proper technique is equally important:

• Always cut just outside the branch collar, where a swelling occurs near the trunk union. Never leave branch stubs.

• Favor thinning cuts that remove full branches at their point of origin on parent stems.

• When shortening branches, make reduction cuts above an outward facing bud or side shoot.

• Clean cuts should be smooth, with bark protected from tearing using sharp by-pass hand pruners or lopers.

• Small branches under 1/2″ diameter can be pruned with manual shears. Use loppers, hand saws or pole saws for larger cuts.

• Disinfect pruning tools with isopropyl alcohol or a 10% bleach solution between trees or cuts on obviously diseased wood.

Take time to make careful, clean cuts. Avoid tearing bark or leaving jagged snags which are entry points for pathogens.

Pruning Precautions

Certain pruning practices should be avoided when working on mulberry trees:

• Never top trees or make heading cuts without regard to growth nodes. This stimulates extensive water sprout development.

• Do not remove more than one-quarter of the tree canopy within a single growing season.

• Avoid pruning branches larger than 2″ diameter unless absolutely necessary. Large cuts are slow to seal.

• Do notpruneduring spring growth flushes when new shoots are rapidly expanding.

• Refrain from pruning after late summer when recovery time before winter is limited.

• Always opt for branch removal rather than stub cuts which die back further.

With care and common sense, pruning mulberry trees at the right time and in the right way will help them thrive for years to come.

Reasons to Prune Specific Types of Mulberry Trees

The pruning regimen may vary slightly depending on which variety you are growing:

White Mulberry

• Requires frequent pruning to control size and maintain productivity.
• Thin dense interior growth for air and light penetration.
• Contains milky sap that bleeds readily if cuts are made improperly.

Black Mulberry

• Prune to maintain a central leader scaffold structure with well-spaced branching.
• Requires less frequent pruning than white mulberries.
• Bleeding is less pronounced after cuts are made.

Red Mulberry

• Prune while young to establish good structure suited for landscape use.
• Mature trees may need only occasional pruning for hazard removal.
• Bleeds moderately from pruning wounds.

Weeping Mulberry

• Requires shaping and thinning cuts to maintain desired pendulous form.
• Susceptible to included bark and weak branch unions if not trained early.
• Low-bleeder compared to mulberry species.

Fruitless Mulberry

• Prune frequently to control vigorous growth.
• Can be maintained as large shrub or pruned to tree form.
• Contains white or pink sap that oozes from cuts.

Match the intensity and timing of pruning to the specific cultivar’s growth habits and pruning tolerance.

Pruning is Vital for Healthy, Productive Mulberry Trees

Pruning mulberry trees is a necessary maintenance task. But determining when to make cuts is just as important as how. While exact timing may vary with tree age, cultivar, and reasons for pruning, the guidelines provided offer a sound seasonal framework. Share this reference with any mulberry tree owners you know who are unsure of when to trim their trees. And feel free to prune this article as needed – unlike mulberry branches, text can be trimmed anytime!