Yes, Japanese cedars turn a rusty brown in winter. For most of them this is normal seasonal color, not a sign of trouble. Japanese cedar winter bronzing is a built-in response to cold weather. The tree greens back up on its own once spring arrives. So before you worry about your tree, know that a healthy plant does this every year. The change is part of how the plant copes with cold, and it happens to trees of all ages and sizes.
My own tree had me fooled the first winter I owned it. By midwinter the soft green needles had gone a deep rusty bronze, the kind of color you see on a plant that is dying. I checked for pests, scraped a twig to see if it was still green underneath, and braced for the worst. Then March came, the days got longer, and the whole tree faded back to fresh green like nothing had happened.
That panic over a cryptomeria turning brown is one of the most common worries gardeners have with this tree. The plant is doing exactly what it should. Cold nights tell the foliage to shift from green to a reddish or purplish bronze. The shade ranges from light tan to dark plum based on how harsh your winter gets. A tree in a windy, open spot tends to bronze deeper than one tucked behind a fence or a wall.
The reason behind it comes down to pigment and cold. As temperatures drop, the green chlorophyll in the needles breaks down faster than the plant rebuilds it. Other pigments that were there all along start to show through, and that gives you the bronze look. The tree slows its growth to protect itself through the cold months, and the color change rides along with that slowdown.
This winter foliage color is reversible, which is the part that catches people off guard. Once spring warms the soil and daylight stretches out again, chlorophyll production ramps back up. The needles green over within a few weeks, and by early summer you would never guess the tree looked half-dead in January. A few cold-climate growers even like the bronze and treat it as a bonus season of color.
How much your tree bronzes depends a lot on the cultivar you planted. Some varieties go a dramatic deep plum, while others barely shift at all. Radicans is the one to know here, since it shows much less winter bronzing and holds a greener look through the cold than most other types. If you want a Japanese cedar that stays green-ish all year, your choice at the nursery matters more than anything you do later.
Before you assume the worst, scratch a small twig with your thumbnail. Green tissue underneath means the tree is alive and just bronzing for the season.
Here is the most useful part. Do not prune the bronzed foliage and do not spray it with anything. There is no fungus to treat and no damage to cut out. Reaching for the shears or a spray bottle only wastes your time. Worse, it can stress a healthy tree right when it is trying to rest. Leave it alone and let the season run its course.
If the winter look bothers you, plant a low-bronzing cultivar like Radicans from the start. That beats fighting the color every year. One smart choice at planting time solves the problem for good. For everyone else, treat the bronze as a sign your tree is healthy and doing its job. Then wait for spring to bring the green back, and enjoy the soft new growth that follows.
Read the full article: Japanese Cedar: Complete Care and Growing Guide
