How and when to prune a yellowwood tree – why arborists say it's vital to trim young trees to ensure a long lifespan

A yellowwood tree can reach 30-50 feet tall and have a similar-sized spread. When properly maintained they offer many potential landscape uses as a great shade or specimen tree. To keep them healthy and guarantee a long lifespan, you need to prune a yellowwood tree to develop a good structure.

The issue with yellowwoods, also known as American yellowwoods, is that they are brittle trees and risk splitting if they are not pruned correctly during their formative years. Not pruning, or doing it incorrectly, increases the likelihood of a tree splitting and not reaching a ripe old age.

Plus, you need to know when to prune trees. Prune yellowwoods at the wrong time and it means sap flows from wounds, leaving them susceptible to pests and diseases. To help mitigate these potential risks, we hear from expert arborists on when and how to prune a yellowwood tree so it lives a long and healthy life.

A guide to help you prune a yellowwood tree

Yellowwoods are native trees suitable for US hardiness zones 5-8 and offer year-round interest, enriching their surroundings with fragrant white blooms in spring and vibrant yellow foliage in fall.

They are not common sights but are wonderful additions if you are looking for a tree for a smaller backyard. To help ensure the longest life for the tree, we look at when and how to prune a yellowwood tree and get expert advice on how to trim and train the tree for a beautiful and long-lasting form.

Why you need to prune a yellowwood tree

The most important reason to prune a yellowwood tree is to develop a strong structure, which helps keep the tree upright and healthy for the longest possible time.

Yellowwood trees are brittle and can fall apart in 30 to 40 years if left unpruned. Not taking the time to prune a yellowwood tree when young to promote a healthy shape can result in it splitting and ultimately being a shorter-lived tree than one trimmed for a good structure.

Pruning will help to promote a beautiful display of hanging clusters of white, fragrant flowers in spring and dazzling foliage color in fall. These blooms are fantastic flowers for bees, though a yellowwood tree may not start flowering until it is ten years old.

When to prune a yellowwood tree

With any tree, it is important to understand the best time to trim to avoid making a tree pruning mistake that puts its health at risk. The yellowwood is a deciduous tree and many deciduous trees are pruned in winter during dormancy. However, yellowwoods are known as ‘bleeder trees’ and that impacts when to trim them.

‘Because of abundant sap flow, it is recommended for major pruning in the summer (after flowering) when cracks are less likely to occur,’ says Chuck Hinkle, the garden supervisor at the Scott Arboretum of Swarthmore College, which houses several large yellowwood trees.

‘Minor pruning can be done in late winter or early spring before new growth starts,’ adds Chuck. ‘Of course, prune dead and diseased branches anytime.’

Pruning in winter or spring can cause excess bleeding from the pruning wounds. The sap attracts insects, making yellowwood trees more susceptible to diseases. Other notorious ‘bleeder trees’ include maples, birches, elms, and walnuts, and it would be a pruning mistake to do major trimming on any of them in winter or spring.

Chuck Hinkle

Chuck Hinkle is garden supervisor at Swarthmore College. He joined the staff in 1998 and was previously a gardener at Friends Hospital in Philadelphia. He holds a B.S. in horticulture from Temple University.

How to prune a yellowwood tree

It is recommended to prune a yellowwood tree when young to develop the structural branches and remove the need for heavier pruning later. Pruning tree branches when young reduces stress, aids recovery, and helps promote a longer lifespan.

In their detailed fact sheet on growing and maintaining the American yellowwood, research arborists Edward F. Gilman and Dennis G. Watson recommend developing branches with ‘a wide angle with the trunk and a U-shaped crotch’ when the tree is young. These branches are pruned to prevent them from growing ‘larger than half the diameter of the trunk’ to prevent splitting.

‘Develop 7 to 10 major lateral limbs spaced along the trunk, not clustered together,’ they add. ‘This will help them develop strong attachments to the trunk and provide for a longer-lived tree than one which is not pruned in this way.’

An established and well-structured yellowwood tree should require minimal pruning. It is vital to remove any dead, damaged, and diseased branches. Chuck Hinkle also removes limbs with ‘weak branch crotches’ that are susceptible to breaking, crossing branches, and ones growing in the wrong direction. Following these guidelines keeps the tree healthy and minimizes the need for major pruning down the line.

Always use clean and sharp pruning tools when you prune a yellowwood tree and take care as they have thin bark that can be easily damaged. A portable tool, such as this garden tool sharpener at Walmart, can easily be used in the yard to keep pruning tools sharp.

As mentioned earlier, birch trees are also ‘bleeder trees’ that must be pruned at the right time to keep them free of pests and diseases. Improper pruning, or over-pruning, can ultimately be fatal for birch trees. To make sure you don’t commit a cardinal sin of bad trimming, see our guide to how to prune birch trees and discover five rules as recommended by professional arborists.