The Art of the Cut: Maintaining Native Trees with Co-dominant Stems

Native Tree Maintenance: To Cut or Not to Cut?

One of the most common questions gardeners face is how to best care for their trees, particularly when it comes to pruning. Native trees, with their unique characteristics and benefits, require specific maintenance to ensure their health and longevity. This article delves into a critical aspect of native tree care: the decision of whether or not to prune when the main trunk of the tree splits into two or more branches.

Understanding the Problem: Co-dominant Stems

The scenario of a tree’s main trunk dividing into two or more branches, often referred to as co-dominant stems, is a significant factor in tree health and structural integrity. This is especially important with certain native species. Co-dominant stems are stems that are nearly equal in size and originate from the same point on the trunk. While they may appear aesthetically pleasing, they can lead to several issues:

• Weak Structure: The point where co-dominant stems originate is a weak point in the tree’s structure. The included bark (bark trapped between the stems) prevents the stems from properly fusing, making the tree susceptible to splitting, especially during storms, heavy snow, or strong winds.
• Increased Risk of Failure: The weight of the stems and the leverage they exert on the weak union can cause the tree to split apart. This can result in significant damage to the tree and potential hazards to surrounding structures or people.
• Reduced Airflow and Sunlight: The dense growth pattern created by co-dominant stems can restrict airflow and sunlight penetration, leading to increased humidity, which makes the tree more vulnerable to diseases and pests.

Identifying Co-dominant Stems

Identifying co-dominant stems is the first step in determining whether pruning is necessary. Observe your trees carefully. Look for these signs:

• Multiple Stems: The presence of two or more stems of relatively equal size originating from the same point on the main trunk.
• Included Bark: Examine the crotch (the angle where the stems meet). If you see bark that’s pinched or folded inward, this indicates included bark, a sign of a weak union.
• Wide Angles: Co-dominant stems typically have wide angles of attachment, which can make them more prone to failure.

The Pruning Decision: When to Cut?

The decision of whether or not to prune co-dominant stems depends on several factors, including the tree’s age, species, overall health, and the severity of the issue. Here’s a guide to help you make an informed decision:

1. Young Trees: Pruning co-dominant stems is generally easier and more effective when the tree is young. Removing one of the stems early on allows the remaining stem to develop a stronger structure. This preventative pruning is often the best approach.
2. Mature Trees: Pruning mature trees with co-dominant stems can be more complex. Consider the following points:
   • Severity of the Issue: If the stems are large and the union is weak, pruning is likely necessary to reduce the risk of failure.
   • Tree’s Health: If the tree is healthy and vigorous, it can often tolerate the pruning. However, if the tree is stressed or has other health problems, pruning may put additional strain on the tree.
   • Aesthetics: Consider the tree’s appearance and how pruning might affect it. While pruning may alter the tree’s shape, it is crucial to prioritize the tree’s health and safety.
3. When to Prune:
   • Dormant Season: The best time to prune most trees, including native trees, is during the dormant season (late winter or early spring) before new growth begins. This minimizes stress on the tree and allows it to heal more quickly.
   • Avoid Summer Pruning: Avoid heavy pruning during the growing season, as this can weaken the tree and make it more susceptible to pests and diseases. However, if a branch is damaged or diseased, it can be removed at any time.

Pruning Techniques: How to Cut?

Proper pruning techniques are essential for promoting tree health and preventing damage. Here’s how to prune co-dominant stems effectively:

1. Choose the Stem to Remove: Select the stem that is less desirable in terms of structure or aesthetics. It is often best to remove the stem with the tighter angle, leaving the one with the wider angle.
2. Make the Correct Cut: Make the cut just outside the branch collar. The branch collar is the slightly swollen area at the base of the branch where it joins the main trunk. Avoid cutting flush with the trunk, as this can damage the trunk and prevent proper healing.
3. Use the Right Tools: Use sharp, clean pruning tools to make clean cuts. Pruning saws, loppers, and hand pruners are all appropriate tools, depending on the size of the branch.
4. Avoid Topping: Never top a tree. Topping involves cutting the main trunk or large branches back to stubs. This practice is harmful to the tree and can lead to several problems, including weak regrowth, increased susceptibility to diseases, and an unsightly appearance.
5. Stagger Pruning: When removing a large branch, it is best to use the three-cut method to prevent the branch from tearing the bark.
   • Cut 1: Make an undercut several inches from the branch collar.
   • Cut 2: Make a second cut from the top of the branch, slightly further out than the first cut, until the branch falls.
   • Cut 3: Make the final cut at the branch collar.

Native Species Considerations

When pruning native trees, it’s important to consider their specific needs and characteristics. Here are a few examples:

• Dogwoods: As mentioned, dogwoods are susceptible to co-dominant stems. Careful pruning of young dogwoods can help them develop a strong, healthy structure. These are best pruned in late winter.
• Oaks: Oaks are generally best pruned during the dormant season to reduce the risk of oak wilt, a disease that can be spread by insects. Avoid pruning oaks in the spring and summer.
• Maples: Some maple species are prone to bleeding sap if pruned in the late winter or early spring. While this is usually not harmful to the tree, it can be unsightly. Pruning maples in late summer or early fall may be preferable.
• Cherry and Plum: These trees are also best pruned in late winter/early spring. These plants can be susceptible to fungal diseases and benefit from pruning when these pathogens are less active.

Professional Help

If you are unsure about pruning your native trees, it is always best to consult with a certified arborist. Arborists are trained professionals who have the knowledge and expertise to assess your trees and recommend the best course of action. They can also perform the pruning safely and effectively. They can also advise on the specific pruning needs of your native tree species.

Beyond Pruning: General Maintenance

In addition to pruning, several other maintenance practices can help keep your native trees healthy and thriving:

• Watering: Provide adequate water, especially during dry periods. The amount of water needed will depend on the tree species, soil conditions, and weather.
• Mulching: Apply a layer of mulch around the base of the tree to help retain moisture, suppress weeds, and regulate soil temperature. Keep the mulch away from the trunk to prevent rot.
• Fertilizing: Fertilize your trees as needed, based on a soil test. Avoid over-fertilizing, which can harm the trees.
• Pest and Disease Control: Regularly inspect your trees for signs of pests or diseases. Take action promptly to address any problems.

Conclusion

Maintaining native trees involves a careful balance of observation, understanding, and appropriate action. Addressing co-dominant stems through proper pruning is crucial for ensuring the long-term health, safety, and beauty of your trees. By following these guidelines, you can help your native trees thrive for many years to come. Remember to always prioritize the tree’s health and consult with a professional when in doubt.