Bronzing 101

Bronzing is one of those plant things that used to freak me out. It’s basically when your outdoor plants begin to change colors to an orange/bronze instead of green. It’s usually because of weather conditions in that little plants microclimate that bring on this change.

What Does Bronzing Look Like?

This is a boxwood in my front yard. In the spring and summer it is lush and green. It starts to look like this about mid winter, and especially after we’ve had some freezing temps. We get some snow in the winter where I live in Washington but it isn’t usually around for too long. Wind is a bigger issue where I live. My boxwoods that are out in the open and exposed to the wind are more susceptible to bronzing.

You can also make sure it is bronzing and not a pest or disease if the leaves and branches are still firmly attached. New growth that was hit by a cold spell is different and you may notice those branches dying back. Bronzing is just a color change and the branches and leaves will be healthy and strong.

What Causes Bronzing?

Bronzing is a stress response from the plant. Drought conditions, excess sun, and wind are all factors that bring this on. In these conditions, the plant has a harder time keeping water in its leaves and chlorophyl is decreased. Chlorophyl is what makes leaves green and when it is lacking, they turn orange or even purplish.

Some species of plants are more susceptible to bronzing as well. I have several types of boxwoods, but there are some that will turn colors a lot easier than others, even when they are planted next to each other. This is another reason to save your plant tags and keep track of which plants they belong to.

Nematodes (small worms) can also cause bronzing. These worms eat away at the roots of plants, specifically boxwoods, and cause the leaves to change colors as a response. The only way to know for sure if this is your problem is to take a sample of soil near the roots of the affected plant to your local extension office (HERE)and have them test it. This is a less common cause of bronzing and not one I’ve had any experience with.

How to manage it

Fortunately bronzing isn’t a huge deal other than physical appearance. When spring comes and the weather calms down a bit, the leaves revert back to their lush green color. Spring is a great time to fertilize and prune (making sure you are past your last frost date) to give those plants a boost of energy and the nutrients they need after a long winter.

I have seen people give their plants an extra watering before a cold snap to help their root systems stay protected and nourished. Burlap wraps can also be used to help protect the leaves and branches from sun and wind. I have personally never done this and my plants have done fine once the season changes.