The Rhododendrons are popular shrubs from the Rhododendron genus. They have been mainstays of late spring due to their gorgeous snowy blooms and large, lush leaves that mostly stay green throughout the year.
The plant primarily grows in Asia; however, it is now found in several surrounding countries due to its attractive looks.
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What Causes Rhododendron Leaves to Turn Yellow?
The Rhododendron plant’s leaves offer an excellent combination of colorful flowers and dark green leaves. However, sometimes the leaves may lose their color due to a wide variety of reasons. One main cause is incorrect soil pH, as the Rhododendron plants are susceptible to changes in their soil contents. Other causes include improper irrigation, inadequate lighting, faulty watering schedule, insufficient nutrient supply, and disease.
Common Causes of Yellowing of the Rhododendron Plant Leaves
When it comes to growing the Rhododendron plants, they are mostly hassle-free; however, occasionally, the plant may create some problems for the owner.
Frequently, the issues are not too severe and can be fixed with just a few alterations in the Rhododendron plant’s care guide.
It is usual for most plants to lose their characteristic color when faced with excess or shortage of food or water. Some common causes for Rhododendron plants leaf yellowing include the following:
Imbalanced Soil pH
The Rhododendron plants are generally tolerant; however, they are quick to react when their soil pH rises above normal. The Rhododendron plants thrive in slightly acidic to neutral soils. Therefore, when the soil becomes too alkaline, the plant develops yellow leaves.
In alkaline soils, the Rhododendron plants soak up excessive amounts of calcium and insufficient iron. Although these are micronutrients, they play a significant role in the plant’s overall structure and leaf color.
You can check your Rhododendron plant’s soil pH with a home pH tester. If the pH is too high or too low, consider replacing the old soil with fresh, nutritious soil or thoroughly wash out the current soil.
Improper Watering
One of the primary causes of the yellowing of the Rhododendron plant’s leaves is an incorrect watering schedule. Most plants, including the Rhododendrons, are sensitive to their watering routines and water characteristics.
In the case of the Rhododendrons plant, the leaves do not like to be directly sprayed. I advise you to either mist the Rhododendron plant’s surroundings or water the soil surface only.
When given too much water, the Rhododendron plant’s leaves react by developing yellow color. They may also turn brown or form necrotic crispy spots on them.
Another minor but significant reason is when the water being used is excessively cold or hot.
Water temperature that is too different from the plant’s average temperature may shock it, and resultantly, the plant’s leaves may turn brown or yellow. If cold water is given persistently, the Rhododendron plant might even die.
Unfortunately, you cannot save the damaged, yellow foliage. However, you can check your water temperature before watering in the future. For the best results, I suggest using lukewarm water only.
Likewise, you should refrain from watering the leaves directly and moisten the Rhododendron plant’s soil’s surface only.
Inadequate Lighting
Like most plants, the Rhododendron plant prefers bright, dappled sunlight. Therefore, when placed in a poorly-lit room with insufficient aeration and a congested space, the plant may respond by turning its leaves yellow.
Similarly, when put in the direct, scorching sun, the Rhododendron plant’s leaves may turn yellow. Maintaining a steady balance between the two extremes of excessive and partial sunlight is necessary to nurture a healthy Rhododendron plant.
I recommend putting your Rhododendron plant in an airy, brightly lit room that receives ample filtered sunlight.
Solar energy encourages new growth and the Rhododendron plant’s characteristic vibrant flowers. Often, northeast and west-facing windows offer just the right amount of sun for most flowering species.
Several plants thrive under artificial growing lights. However, this is not the case with the Rhododendron plant. For healthy growth, place the plant under natural, dappled sunlight.
Fertilizing Needs
Another significant cause for the Rhododendron plant leaves turning yellow is improper fertilization. The yellow leaves may signal that the plant needs a more generous amount of nutrients.
Good quality fertilizer is imperative for any plant’s healthy development; I suggest buying a slow-release high-quality fertilizer, made especially for Rhododendron plants.
Another option is to use a diluted liquid fertilizer. Spread the fertilizer evenly over your plant’s soil once or twice a month, or follow the product packaging guidelines.
Alternatively, your Rhododendron plant may develop yellow leaves when it cannot soak up the provided feed efficiently. When faced with such a difficulty, I apply fertilizer to the soil when it is moist; this ensures maximum absorption.
Salt Accumulation
As much as you admire your Rhododendron plant, fertilizing it repeatedly can also lead to numerous problems, one of them being yellow leaves. The Rhododendron plant is a fairly large plant; however, feeding it over and over again is not a good idea.
The Rhododendron plant may also form yellow leaves when an excessive amount of salts has accumulated in its system. While plant feed can be a significant source of salt buildup, chlorinated water falls right behind.
Furthermore, not washing out your Rhododendron plant’s soil at least thrice a year can also cause considerable damage.
To prevent salt buildup, avoid overfertilizing your Rhododendron plant and use room-temperature low-chlorine water only. For fertilizing, use good-quality feed once a month only.
To get rid of the salts in the water, fill up a bucket and let it sit overnight; the excess salts will settle at the bottom.
Likewise, to eliminate the salt accumulation in your Rhododendron plant’s soil, wash it out about four times a year.
Repotting
The Rhododendrons are decently-sized plants with a moderate growth rate. Repotting it yearly is not essential; however, it usually needs repotting every two years.
A plant’s soil may lose its natural texture and nutrient content as it ages. Growing the Rhododendron plant in such a soil mix can retard its growth, as the plant cannot uptake enough food and water.
After approximately two years, repot your Rhododendron plant into a slightly larger pot with an appropriate soil mix. The potting mix should ideally contain pine bark, peat moss, and some sand.
Humidity Requirements
The Rhododendrons plant prefers moderate moisture levels, ranging from 60% to 80%. These levels are quite high; therefore, maintaining them can sometimes be troublesome.
If put in low moisture, the plant may turn its leaves yellow. To solve this problem, mist your Rhododendron’s surroundings or group your houseplants.
You can also purchase a moisture meter to accurately measure humidity levels in your house.
Diseases and Pests
A common cause for leaf yellowing in the Rhododendrons is fungal infections or pest attack. If you notice yellow patches or blotches on your plant, it may be diseased or infested by spider mites.
Spray some fungicide spray on your Rhododendron plant and keep its environment clean.
Frequently Asked Questions About The Rhododendron Plant
How do I fix the drooping leaves of my Rhododendron plant?
Lumpy, drooping leaves are mostly a result of overwatering. Please remove your Rhododendron plant from its current soil, wash its roots thoroughly, and pot into a well-draining container. Furthermore, add some fungicide spray to the plant.
Why are my Rhododendron plant’s leaves yellow and curled?
Yellowing and leaf curling in Rhododendrons can occur due to various reasons. Please review your plant’s feeding and watering schedule and make changes appropriately. Moreover, ensure that it is placed in dappled sunlight.
When should I repot my Rhododendrons?
When your Rhododendron plant grows leggy, stretched vines, you may have to repot it. Transfer the plant into a slightly bigger pot with good drainage and aeration.
Daniel has been a plant enthusiast for over 20 years. He owns hundreds of houseplants and prepares for the chili growing seasons yearly with great anticipation. His favorite plants are plant species in the Araceae family, such as Monstera, Philodendron, and Anthurium. He also loves gardening and is growing hot peppers, tomatoes, and many more vegetables.