Arborvitae is an evergreen tree. It is similar to juniper or pine but with certain differences in foliage, size, and growth patterns. It is part of the Thuja genus which contains the Thuja occidentalis (Northern White Cedar and Eastern White Cedar) and the Thuja plicata (Western Red Cedar).
Within this arborvitae family, there are multiple varieties and not all of them act the same when winter rolls around. So if your Arborvitae is turning yellow, don’t immediately fret. Most of them naturally change color in the winter.
Despite being evergreens and not losing their leaves in the fall and winter, Arborvitae will indeed change color. In the spring, the color should change back to normal.
Arborvitae leaves may turn yellow for a number of reasons: change of color during winter season, overwatering, underwatering, pests, disease, or a lack of nutrients.
How Do I Know if My Arborvitae Is Dying?
There are some clear signs to indicate that your Arborvitae is dying. When you start to see these signs, it is good to react quickly to save your plant.
There are six main signs to look for:
- Cracked and brittle bark. The texture of the bark on an Arborvitae will change when the plant is dying. It will loosen from the tree and show a lot of cracks.
- Most of the leaves are brown or have fallen off. Arborvitae is an evergreen plant. It will have some leaves in the process of dying off all year round. Also, some species of Arborvitaes tend to have leaves that naturally obtain a yellow or brown hue. However, if a large number of leaves have fallen off it is not a good sign.
- A lot of the wood is dead. It is normal for some wood or branches of a plant to die. However, if most of the branches and limbs start dying, then your plant isn’t doing well.
- An abundance of pests or fungi. Certain pests like bark or carpenter beetles can live in the plant and slowly cause it to die. Same with fungi which can lead to diseases such as Cankers.
- Damage to the roots. Arborvitae’s roots are underground, but if they get damaged due to nearby construction, or competition for space, then they may start to die due to lack of access to nutrients.
- Under the bark is dead. If you peel away the bark and cut into the tree, you should see signs of green and life. If you don’t, especially around the trunk, it is a good sign that your plant is dying and the root cause needs to be addressed immediately.
Do Arborvitaes Turn Yellow in the Winter?
There are some Arborvitae cultivars out there, such as the Emerald Green, that have been bred to combat yellowing in winter, and to stay the same green all year round.
However, be prepared for the foliage of other varieties of Arborvitae, such as Holmstrup and DeGroot’s Spire, to change color in the colder months.
By treating the plant the same all year round, such as by continuing to water your plant with the same amount and frequency, you may have some success in reducing the amount of yellow or brown leaves.
These changes are not necessarily a sign of a dying or injured plant, but rather just their natural seasonal color variation.
Why Are My Arborvitae Inner Leaves Turning Yellow?
If it isn’t winter, or if you have a variety like the Emerald Green that isn’t supposed to be affected by seasonal color changes, and you still notice yellowing leaves on your Arborvitae, then that is a sign that something is wrong. It could be a symptom of too much or too little water.
A certain amount of yellow leaves are normal. Since they don’t shed all at once, the leaves of an Arborvitae will fall and shed in small bursts throughout the year. So if you are only seeing a little bit of yellowing that shifts throughout the year, then that is normal.
However, if you are seeing a large amount of yellowing, it could be due to irregular watering or perhaps too few nutrients. Or even something more serious like pests or disease.
Why Is My Newly Planted Arborvitae Turning Yellow?
If you just transplanted your Arborvitae and it is turning yellow, it might be transplant shock. Transplant shock occurs when the roots of your plant were damaged during the transplant, or if the plant has undergone exposure to extreme conditions and climate changes.
Immediately after transplant, you want to make sure the soil around your Arborvitae is moist so that your plant can grow and thrive. If the roots dry out while a plant is trying to recover after a transplant, then they may start to turn yellow.
Will Yellow Arborvitae Turn Green Again?
If your Arborvitae changes color due to seasonal changes, the yellow will eventually turn back to green. If the yellowing occurred due to an injury or sickness of the plant, the yellow will likely not go away.
However, when those affected leaves die and fall off, then the new leaves that replace them will be green again.
How Do You Fix a Yellow Arborvitae?
To fix a yellow Arborvitae, you have to first identify the source of the problem. If it is due to fungus or pests, removing the branches of a plant that are dying or dead is an important step to take to reduce the problem. You can also use fungicides and insecticides around your plant to help get rid of the infiltration.
If it is due to over- or underwatering, you need to first identify which it is and then adjust the amount of water accordingly. A general rule of thumb for Arborvitae is that you want to give the tree about 10 gallons (37.85 liters) of water a week per inch of the diameter of the tree.
Now, you don’t want to give the plant all 10 gallons at once. Using a slow-drop method or giving a gallon or two of water a day is the better option.
Rain counts as some of that watering, so you don’t want to give your plant 10 gallons of water a week unless you live in a dry climate where it hasn’t rained in a while. You will likely need to adjust watering throughout the year depending on the climate and season.
Arborvitae can survive drought conditions for a while, so it is better to underwater them than overwater. However, chronic underwatering can still cause problems.
If your plant starts to look like it is rotting, or it has fungal rot around it, you are likely overwatering your plant. Try letting it dry out for a few days before resuming watering and think about reducing your weekly watering a little.
If the soil is dry every time you go to water, your plant may just not be getting enough water. Try to increase your amount a little, and see if your plant springs back.
If your plant is lacking nutrients, using a liquid fertilizer around the roots can help provide some of the nutrients. Try to find one that has 50% nitrogen. Something like a 12-6-4 or 10-8-6 NPK (nitrogen, phosphorus, potassium) ratio is best.
How Do You Keep Arborvitae Healthy?
To keep your Arborvitae healthy, you have to take steps to keep them in an ideal environment. They prefer moist, but well-draining soil, a pH of 6 to 8, full sun, and high humidity.
By matching as many of these ideal growing conditions as you can, you can keep your Arborvitae healthy and reduce the yellowing of your plant.
Certain elements will be out of your control, such as pests or fungus, so taking steps to mitigate those problems as they arise is also important. For this reason, always pay attention to any changes in your Arborvitae, as they may be early warning signs.
Despite being an evergreen, Arborvitae does typically change color based on the season. However, its yellow or brown leaves will not fall off and die like those of deciduous trees.
Some Arborvitae varieties, such as the Emerald Green, don’t typically change color during the winter months. If you have one of those cultivars or a standard variety and notice yellowing outside the winter months – there may be something wrong. The most common reasons for yellowing of the leaves are: underwatering, overwatering, pests, disease, or lack of nutrients.
Identify what is causing your Arborvitae to change color based on the signs and conditions and then adjust your care as necessary to ensure your plant becomes happy and healthy once again.