Why is the tree turning brown? You will have to Test the trunk with your nail till you get to a green part. Before you can take any steps to fix the problem, you need to figure out why your tree is turning brown. Exposure to cold winter winds, dry conditions and frost contributes to boxwood leaves turning brown, reddish-brown, orange or yellow. These can occur on the stem from the soil line to the shoot tips. I have a pair of box topiary at my south facing exposed front door. Two of my dwarf Alberta spruce has a problem that causes the needles to turn brown and fall off. Folks, if you have leyland cypress trees, then you've probably noticed that at times, part- or all of the trees- may turn brown. In fact, winter becomes the most common season for spotting brown foliage on otherwise green boxwood shrubs. Scape the trunk on the top with your fingernail. The top of the topiary may be dead (die back). Box Blight . Black, elongated, streaking lesions may also be visible on the stem. If it is dry brown and not green it is probably dead. If your plant isnât over-watered but youâre still wondering why rosemary has brown tips, look to recent changes in lighting conditions. Iâm not sure what I have done wrong, and would love some advice on how to care for them back to full recovery. Junipers (Juniperus spp.) Actually, there are numerous reasons why an evergreen might start turning brown. When there are whole brown leaves on a plant, this can indicate several dozen problems; but when just the sides or tips of the leaf turn brown, there is only one problem â the plant is stressed. the other is. hi all. Boxwood (Buxus) are wonderful evergreen plants to formalize the edge of a border with a low hedge or grown into a larger shrub to make topiary shapes. Dying Topiary ... ago. These spots eventually grow larger and coalesce before turning brown or straw-like and dropping to the ground. There are a number of diseases that could be the culprit; there could also be a problem due to a lack of nutrition in the soil. Terracotta pots placed on your Terrace or Patio look fabulous containing carefully clipped box balls and topiary triangles. Firstly lets have a look at the problem from a web site on the net: This process, known as bronzing, does not cause permanent damage to boxwood shrubs. I have tried insecticide and fungicide to control the problem. Box plant leaves will go a coppery brown colour if the plant is short of nutrients, or if it is exposed to very cold winds, or to prolonged frosty weather. There are several reasons why this may happen. I recently noticed some brown limbs and looks like dying. The same watering policy for outdoor plants should hold for potted rosemary â it should never be left in a saucer of water or the soil allowed to remain wet. Brown leaves on Box plants, How to treat Box Blight Beautiful Box Trees. Cut the trunk at this part or the die back will continue down the trunk and kill the plant completely. Then a disease appeared which has caused great problems for both nurseries and home gardeners. The same plants have been used for topiary as well. They have survived extremely cold winters. are needle-leaved evergreens that are used in many landscapes. I have feed and pruned them each spring. they have been there since April but one of them is getting patchy brown leaves. Potted Rosemary Turning Brown. Q. Most commonly brown leaf tips or brown edges on leaves are caused by the plant not getting enough water. My Juniper Needles Are Turning Brown & Falling Off.