Don't Panic! Your Evergreens Are Just Bronzing

Evergreens are celebrated for their steadfast greenery, offering year-round color even as the rest of the landscape fades. But when winter arrives, you may notice some of your precious evergreens taking on a bronze or rusty hue. This change often raises questions: Is this normal? Are my trees in trouble?

The answer lies in the fascinating way evergreens adapt to survive the season. In this blog, we’ll explore the phenomenon of winter bronzing, look into the causes, and explain why this natural transformation is not only harmless but also evidence of the resilience of evergreens.

Understanding Winter Bronzing  

Winter bronzing is the seasonal discoloration of evergreen foliage, where the vibrant greens of summer fade into hues of bronze, rust, or yellow. This transformation occurs primarily in response to environmental stressors like colder temperatures, wind, and winter sunlight. While it might seem alarming at first glance, it’s a natural process that helps evergreens survive the harsh conditions of winter.

The bronzing effect is most noticeable on older needles—those that are two to three years old. These older needles are located on the inner part of the branches, closer to the trunk. Unlike the fresh growth at the tips, which remains lush and green, the older needles begin to change color as part of the tree’s natural cycle.

As the seasons progress, these older, bronzed needles often drop from the tree entirely. This process, known as needle shedding, is completely normal. Evergreens aren’t truly “evergreen” in the sense that they keep all their needles forever—they simply shed and replace their needles in a gradual cycle. Growers don’t worry about this, because the process is all part of the seasonal cycle.

The location of the bronzing and needle drop, usually on the interior of the tree, is a key indicator that this is a natural occurrence rather than a sign of damage or disease.

The Science Behind Bronzing  

The color change, or bronzing, is a clever way evergreens protect themselves during winter. In cold weather, evergreens face two big challenges: freezing temperatures and bright winter sunlight, which can be harsh and damaging.

To cope, they produce special pigments like anthocyanins, which act as sunscreen, shielding needles from excessive sunlight and preventing damage. These pigments also give fruits, vegetables, and evergreen needles their vibrant colors - producing a reddish-bronze hue.

At the same time, the green pigment, chlorophyll, becomes less active in winter, allowing the protective bronzed pigments to stand out more. Together, these changes help the tree stay healthy and ready to thrive again when spring arrives.

Commonly Bronzing Evergreens  

Not all evergreens experience bronzing, but it's a common trait among specific species such as Arborvitae (primarily Thuja), Chamaecyparis, and Boxwood. The degree and intensity of bronzing can vary between species, making it a distinctive characteristic rather than a defect.

Is Bronzing Harmful to Evergreens?  

In most cases, bronzing is a natural and harmless process - a process so harmless that growers don’t concern themselves with it. Once temperatures warm in the spring, these trees usually return to their vibrant green state. However, excessive bronzing or foliage that remains discolored well into the growing season might indicate other issues, such as dehydration or disease.

How to Minimize Bronzing  

While it’s important to acknowledge that bronzing is natural, there are steps you can take to minimize its intensity:  

1. Proper Hydration: Ensure your evergreens are well-watered before the ground freezes to prevent dehydration stress.  
2. Establish a 3-foot wide care bed - An established care bed provides essential nutrients and insulation, helping trees combat stress and ensuring their long-term health.

It’s worth reiterating: bronzing is a natural response. As long as your trees look healthy overall, there’s no need to worry.  

Winter bronzing is nature’s way of ensuring evergreens survive harsh conditions. Rather than seeing this as a flaw, view it as a seasonal transformation—a unique reminder of how resilient evergreens can be. So, instead of trying to “fix” what isn’t broken, embrace the bronze!