The Best Time to Prune Black Walnut Trees

Black walnut trees are prized for their beautiful wood and delicious nuts. Pruning is an important part of maintaining healthy black walnut trees and maximizing nut production. But when is the ideal time to prune these majestic trees? In this article, we’ll explore the pros and cons of pruning black walnuts during dormancy versus during the growing season.

Pruning Black Walnuts in Dormancy

The traditional recommendation has been to prune black walnut trees during the dormant season, generally from January through March. There are a few reasons why dormant pruning has been the standard approach:

• Less sap flow – Pruning during dormancy results in less sap bleeding from the cuts Excess sap can attract fungus and diseases

• Drier conditions – Late winter and early spring are typically drier than other times of year. Damp conditions also promote diseases.

• Easier to see structure – Without leaves, it’s easier to see and evaluate the overall branching structure

• Less stress – Pruning when the tree is dormant arguably results in less stress than removing foliage and branches during the growing season.

• Faster wound closure – Some research shows wounds seal over faster when pruning is done just before spring growth starts.

For many years, pruning black walnuts during dormancy from January to March has been the recommended timing. And for good reason – it avoids many of the potential downsides of pruning during the growing season.

Shift Toward Growing Season Pruning

However, over the past couple decades, there’s been a shift toward summer pruning of black walnuts instead of dormant pruning. Here are some of the benefits that proponents of summer pruning point to:

• No sap flow – Pruning in summer eliminates the messy sap bleeding from pruning cuts.

• Lower disease risk – Summer conditions are less hospitable for disease organisms to infect pruning wounds.

• Better form correction – Branches are more pliable during the growing season, allowing for better form adjustment.

• Less regrowth – Research shows summer pruning leads to fewer water sprouts from the trunk.

• Assess foliage – With leaves present, it’s easier to judge how much foliage will be removed by each cut.

• Pleasant conditions – Pruning in summer avoids cold, wet early spring days.

While growing season pruning conflicts with the conventional wisdom, it actually may be advantageous in many circumstances.

Key Timing Considerations

So when is the single best time to prune black walnut trees? As with most things in nature, there’s no one-size-fits-all answer. Here are some key timing considerations:

• January to March – The traditional window for dormant season pruning. Lower disease risk but more sap flow.

• June to July – After spring growth but before summer heat peaks. A nice compromise between dormant and summer pruning.

• November to December – After leaves drop but before heavy winter. A good option butsap may still flow.

• Avoid April and May – Don’t prune when leaves and flowers are emerging. Excellent time for disease infection.

The “early” and “late” dormant seasons (November-December and January-March) offer a good balance of benefits without as much sap flow or disease risk. June-July is ideal for summer pruning in most regions. Avoid the spring growth flush at all costs.

Pruning Approach

In addition to timing, proper technique is critical for success:

• Prune branches at the branch collar to avoid trunk wounds.

• Use clean, sharp tools to make precise cuts. Disinfect tools between trees.

• Always prune from the top down, removing inward-facing and competing branches first.

• Take off no more than 25% of the canopy in one season.

• Focus on limb removal in the center and top to allow light penetration and air circulation.

With the right timing and practices, pruning black walnut trees can maintain good structure and vigor. Consider both dormant and summer pruning depending on your needs and circumstances.

Black walnut trees thrive with occasional pruning, but the ideal timing is widely debated. The merits of dormant season versus summer pruning both have ardent supporters. In reality, there are advantages to pruning black walnuts across much of the year as long as proper techniques are followed. Focus on removing the right branches and avoiding disease windows in early spring and summer heat waves. With diligent pruning and care, your black walnut trees will provide bountiful harvests for generations to come.