Arborvitae is a member of the Thuja genus. They are coniferous trees and belong to the Cupressaceae family. With Emerald arborvitaes – whether newly planted or old – turning yellow can often be a cause for concern.
Many times the yellowish coloring might not be an anomaly. New and freshly planted arborvitae often grow in tints of light green and yellow. In shedding months, like autumn, arborvitae can naturally turn yellow, but they regain their vibrant color in time.
Attention should be paid if only the new growth is turning yellow and if the previous year’s growth is turning yellowish-brown. This can be a sign of deeper issues.
If your arborvitaes are suddenly discolored out of season, it is possible that the problem lies in the watering habits. It could also be a sign of pest damage or blights. There is a chance the pines are turning yellow because they are not planted correctly.
There could be several issues, and to be sure; it is important to inspect the plant thoroughly and adjust watering schedules accordingly. If the problem does not lie with irrigation, then it could be lacking nutrients. Let’s find out the reasons for the arborvitae turning yellow and how to overcome this issue…
Why Is My Arborvitae Turning Yellow?
Arborvitaes shed a year’s worth of leaves, even though they are evergreens. Sometimes, the yellowing may not be a cause for concern, but it can indicate a deeper problem if the shedding is an anomaly and out of season. Here are some of the causes for your emerald arborvitae turning yellow.
Proper watering, especially in the initial planting days, is crucial. The arborvitae plants often need a lot of water and can turn yellow if too little or too much water is given to them.
If they are watered too frequently, and the soil is saturated, then that can cause waterlogging. Waterlogging can then lead to loss of roots as well. It is essential to keep the soil moisturized but not waterlogged.
On the other hand, if the arborvitae remains under-watered, it can cause the leaves to be yellow or brown due to stress. Care should be taken to adequate water the arborvitae in the dry periods as too little water with an excess of sunlight causes discoloration. Ideally, one inch of water weekly works well.
If the plant has been underwatered, then it is needed to hose the plant and let it soak the water from top to bottom. Often the plant might need to be watered for several minutes.
Although fairly resistant, arborvitae can occasionally suffer from pest damage, leading the pines to turn yellow. Phytophthora is a root rot that causes the root of the arborvitae plant to turn yellow.
The cypress tip miners can also be causing yellow discoloration. The offsprings of cypress tip miners often consume the plants’ twigs, and the affected parts can get damaged. The affected parts can turn yellow and even darker in winter. You can use neem oil (Amazon link) to make sure there are no pests.
Lack of Proper Nutrients
Like many plants, arborvitae also requires additional nutrients to thrive. This can come from compost, mulch, or fertilizers. Fertilizers are needed if the plant lacks required nutrients like nitrogen, potassium, zinc, iron, etc. My favorite fertilizer is Miracle Grow (Amazon link).
Aside from fertilizers, the soil’s pH levels should be optimally maintained, and testing the pH can determine the deficiencies in any.
Often iron deficiency is the cause of such matters, and a spray of iron chelate foliar can be used to correct the deficiency.
Since the deficiencies often emerge in the form of chlorosis of the newer and upper parts of the plant, they can be easy to spot. But it can also be misleading, so it is better not to treat the pant for deficiencies unless the deficiency is confirmed.
If the arborvitae is a newly planted tree, it may be dealing with some environmental stress due to the new location. In the event of any transplantation taking place, the plant can go into transplant shock. It is a stressful condition for the plant and points towards poor adjustment of the roots in a new environment. This becomes apparent due to the foliage turning yellowish or brownish.
If only the inner branches are turning brown or yellow while the puter remains lush green, then that is no cause for any concern. It is common and part of the process.
Improperly or poorly planting the emerald arborvitae can also cause the yellowing of the plant. It is one of the most common problems when planting new arborvitae plants. Fortunately, the plant can be set right after re-digging it and planting it correctly, even if months have passed.
There are chances to save the tree even after 18 months of poor planting, but caution should be exercised. But if the problem resides in planting methods, then other measures like irrigation, fertilization, etc., will likely fail to give results.
The only way to improve a poorly planted tree’s growth will be to replant it correctly if it is not too late. Caution should be exercised to not plant your arborvitae too deeply into the potting soil. Instead, plant it closer to the top with the highest roots on top of the soil.
Often the cause of the arborvitae turning yellow can be a simple case of an animal, specifically dog damage. If a dog is peeing on the arborvitae plant or around it, it can alter the soil’s nitrogen levels. This can easily be remedied by preventing the dog from urinating on and around the plant.
The urine can often turn the plant yellow and gradually darken it to brown.
In cases of leaves that do not turn back green, it is best to cut them and invite newer growth. In most cases, once the leaves have turned yellow, they rarely turn back into their lush emerald color again.
Diseases and Blights
Another cause of your arborvitae turning yellow could be diseases and plant blights like Pestalotiopsis tip blight or black flagging. Blights can thoroughly damage the plant if not treated immediately. It is best to cut the damaged parts and ensure the plant is appropriately treated and protected against disease.
Stopping Arborvitae From Turning Yellow
For newer plants, it is easy to overwater them. The best way to stop arborvitae plants from turning yellow is to minimize improper irrigation, which typically means watering it up to 1 inch weekly.
Sometimes the plant may need more water. Especially if it is in the initial planting stage, then it will be fine to water it more. Otherwise, weekly or biweekly watering of the plant should be enough.
When treating the plant infected with pests, the damaged parts should be cut and disposed of. Neem oil (Amazon link) can be sprayed on the plant to prevent further damage.
The plant should also get properly direct sunlight, so it is crucial to make sure nothing hinders the direct exposure.
For lack of nutrients and deficiency, use proper fertilizers and nutrient sprays to promote the plant’s healthy and robust growth.
When questioning, “Why is my arborvitae turning yellow?” it can be easy to implement the wrongful measures. That can not only increase the damage but also leave your plant further dry and dull. It is important to understand the reasons for the yellowing of the plant before implementing measures to rectify the yellowing.