Boxwoods turning yellow is a worrying issue because it is most likely caused by diseases, pests, or poor maintenance. All of these conditions put the plant under stress and the result is discoloration accompanied by wilting.
If you are concerned about this issue and wish to see your boxwoods lush and green at the earliest, then this is the right article for you.
We help you identify the most common causes that are causing the condition and also provide the most effective solutions to fix this issue, so read on to know it all!
Why Are Your Boxwoods Turning Yellow?
Your boxwoods are turning yellow due to salt damage, under watering, leafminers, volutella stems canker, or macrophoma leaf spot. It might also be due to boxwood root rot, nematodes, blight, pest infestations, winter burns, aging, poor maintenance, and lastly, a normal change in color after pruning.
– Salt Damage
This a concern that is not noticed most of the time, but if you have been using salt to remove the ice from your sidewalk or pathway, then this could be causing potential damage to your boxwood shrubs.
The salt that you apply can accidentally spray and leech into the soil and leaves. This can damage the gentle plant tissues and also hamper the water balance at the roots, preventing it from functioning in the right manner.
The damage caused may not be noticeable immediately, however after winter in the spring months you will notice yellow leaves when they are supposed to be in their blooming season instead. If you look at the shrubs properly, the boxwood might be dying on one side, especially closer to the walking path.
– Underwatering
Underwatering these green shrubs can cause them to turn yellow and make them look weaker. The shrubs are indeed hardy, however they require regular watering otherwise they will suffer from dehydration and drought stress.
This sort of discoloration will generally occur in hot sultry weather when the soil tends to get dry, turning chlorotic and leading to inadequate absorption of nutrients.
– Boxwood Leafminer
Boxwood leafminer is a common insect that lays its eggs in the layers of leaves of boxwood shrubs. The eggs of these insects develop into larvae, which in turn feed on the tender tissues of the foliage.
On the other hand, it would get even more damaging as the adult leafminers tend to eat the leaves, leaving behind noticeable holes all over the shrub. The infestation turns the leaves yellow, along with brown patches and early leaf-dropping when it gets severe.
– Volutella Stem Canker
Volutella stem canker condition is a fungal disease caused by the fungus called pseudonectria buxi. The infection results in boxwoods turning yellow-orange with spots found on the underside of the leaves.
In case of severe infections, the branches can become loose and die back, ultimately leading to the death of the shrubs. You will notice the occurrence of this fungus in generally wet and rainy climates.
– Macrophoma Leaf Spot
This is another fungal disease that is caused by macrophoma candollei. The fungus causes lesions in a yellow or reddish brown color, all over the surface of the leaves. It sporulates on the underside of the leaves, as they would be leaving behind black fruiting spots.
– Root Rot
Root rot is one of the issues that is caused by the fungus phytophthora sp. The fungus will appear if the plant has been exposed to excess humidity or overwatering. Additionally, if you have let the roots sit in water for a long time it becomes moist, making them susceptible to root and crown rot.
You will notice yellowing, wilting, and occasional brown spots on the foliage. Root rot also makes the boxwood grow slow and stunted, along with developing upturned curled leaves. Since the roots are damaged, the foliage would start turning yellow as water would not nourish the leaves like the healthy leaves would.
– Nematodes
Nematodes are pests that are microscopic and are seldom visible to the naked eye. However, these thrive on the roots of the shrubs, making them weak and limp. It prevents the roots from absorbing adequate oxygen and nutrients from the soil, thereby turning the plant foliage yellow.
– Boxwood Blight
This is yet another fungal disease, and the first early symptoms you will notice are yellowing leaves and occasional cases of boxwood turning brown. Additionally, the leaves will fall well before time.
Boxwood blight is generally caused if you’re using contaminated soil carried from the initial stages of the plant’s life, which is the nursery.
It can also spread from plant to plant quickly or if you have used unsanitized tools to prune. If the condition is not tackled, it can damage your entire boxwood shrub. In addition, you would even be wondering why the boxwood is turning light green. Basically, they become light green before they turn yellow because of blight.
– Pest Infestations
Pests such as mealybugs, spider mites, leaf miners, and boxwood psyllids are common pests that attack boxwoods. The infestation can get worse if the shrubs have been exposed to some sort of stress, thereby making them more susceptible to any form of damage by the pests.
Pests feed on the foliage and leave behind the larvae on the underside of leaves, which can result in discoloration such as yellowed leaves.
Leaf miners are tiny flies and the larval stage is the most dangerous as they dig into the plant’s foliage and result in blisters all over the surface apart from the yellowing. Psyllids are about 1/8th of an inch. They feed on the foliage and turn them yellow in just a short period of time.
– Winter Burn
Winter burn is when the shrubs lose water through their leaves in excess cold and frost conditions. During winters, the roots and the soil tend to freeze and are unable to absorb much water to transport them across the shrub.
Coupled with chilly winds, they struggle to cope and under the stress situation at freezing temperatures, the winter damage results in the boxwood turning yellow in summer.
– Aging of the Leaves
Boxwood Bush leaves also go through a normal aging process. This is not a matter of concern as the changes occur over time and the leaves turn yellow and fall to accommodate new ones. You don’t have to be worried as much, as long as they are not falling well before time.
– Poor Maintenance
Regular maintenance is needed to keep these plants healthy and thriving. An irregular watering schedule, over-fertilizing, and an imbalance in the soil pH are all common maintenance issues that make the boxwood prone to developing yellowed leaves.
Additionally, boxwood is a shrub with a naturally rounded form, thus, over-pruning can damage its tissues, putting it under stress and turning the leaves yellow.
– Change in Color Post Trimming
If you are concerned not only about the yellowing but also about why your boxwoods are turning brown post trimming, then do note that this is normal and the plant should recover in a couple of days. You may notice your boxwoods turning brown and yellow after a prune, and the key way to tackle it is by pruning in early spring.
How To Fix Boxwoods Turning Yellow
To fix your boxwoods turning yellow, you have to provide pest control and control the diseases and fungi that are plaguing your plant. In addition, you should also maintain a proper watering schedule and resolve root rot. You should also tackle the winter burn and stem canker voluntella.
– Control Pests
The best way to control pests on boxwood shrubs is to regularly inspect them for infestations or colonies. As soon as you see such signs, snip the section away. This will prevent their spread to other sections, and you could reduce the yellowing to a great extent.
Additionally, spray a diluted soapy solution so that the eggs fall off the plant. You can even apply organic neem solutions, as the pests are repelled by their odor. Repeat the procedure once every two days along with a jet spray with which you can blast water on the affected area.
– Control Diseases and Fungi
Prune the affected sections before they spread to the other sections of the bushes. Treat the plant with an organic fungicide, which will reduce the impact of the disease and curb its spread.
In addition, prevent the occurrence of such diseases by always sterilizing all tools and equipment before use. Reduce moisture around the plant and soil so that the plant is not susceptible to fungal growth.
– Maintain a Proper Watering Schedule
Boxwoods do not like excessive amount of water but at the same time do not survive in drought conditions too. Thus, water the plant regularly depending on the climatic conditions, scaling back in winters and increasing the frequency in summers.
Your soil should always be lightly moist, and never let the roots sit in water for a long time. When you do this, you will overcome the issue and solve the problem of how to revive a dying boxwood shrub.
If you are living in an extremely dry zone, mulching will help to keep the soil slightly damp, and it also reduces the rate of evaporation of water, thereby keeping the boxwood well hydrated. These steps will prevent the shrubs from turning yellow. Also, if you are thinking about whether you should trim yellow leaves on boxwood, then the answer is yes.
– Resolve Root Rot
If you suspect root rot, the first thing to do is to stop watering the plants. Let the soil completely dry out. You could poke tiny holes in the soil so that air enters in and the water can evaporate faster.
It is recommended that one prevents the occurrence of this condition by ensuring there is never water logging at the base of the soil, along with providing proper drainage for excess water to leave.
– Tackling Winterburn
The best way to tackle winterburn is to apply an anti-desiccant spray, which will act as a preventive layer and reduce the amount of water the plant will lose. After that, you must water the bushes normally and they will recover in no time.
– Tackle Stem Canker Volutella
To tackle volutella blight, reduce the humidity around the plant by trimming and removing all the infected branches. Spray a copper-based fungicide and repeat the action every few weeks, and you will notice new growth occurring soon.
With these tips, you don’t have to worry anymore as you will be able to keep the lush green leaves on your boxwood shrubs intact.