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You may baby your rhododendron, but the popular shrubs can’t cry if they are not happy. Instead, they signal distress with yellow rhododendron leaves. When you ask, “Why does my rhododendron have yellow leaves”, the answer could be anything from improper irrigation to incorrect planting to inappropriate soil. You’ll have to evaluate your cultural practices to determine the problem and take appropriate steps for treating yellowing rhododendrons.
Yellow Leaves on Rhododendrons? Here’s What to Do
If you have rhododendrons in your garden, you may notice the leaves turning yellow from time to time. While some yellowing is normal, excessive yellow foliage is often a sign of trouble that requires action. In this article, I’ll explain the top causes of yellow rhododendron leaves and share tips for fixing the problem.
Causes of Yellow Rhododendron LeavesThere are several potential reasons rhododendron leaves may turn yellow, including
Improper Soil pH Rhododendrons prefer acidic soil with a pH of 4.5-5.5. If the soil pH rises above 6.0 the plants can’t properly absorb nutrients like iron which leads to yellowing leaves (interveinal chlorosis).
Nutrient Deficiencies: Lack of nitrogen, phosphorus, potassium, or iron can all cause uniform yellowing on older and newer leaves. This often happens after blooming when the plant is nutrient deficient.
Excess Sun: Rhododendrons thrive in partial shade or dappled sunlight. Too much hot, direct sun will cause yellowing on exposed leaves.
Extreme Temperatures: Heat and cold extremes stress rhododendrons. This makes them prone to yellow leaves and leaf drop.
Excess Water: While rhododendrons like moist soil, soggy roots choke off oxygen causing overall yellowing and leaf drop.
Pests & Diseases: Insects like lace bugs leave tiny yellow spots on leaves. Fungal issues also cause splotchy yellowing and wilting.
Plant Stress: Anything that stresses the plant like poor drainage, drought, or trauma can lead to yellow leaves and leaf drop.
Old vs New Leaves Yellowing
Take note of where the yellow leaves are on your rhododendron. Older leaves turning yellow near the bottom of branches is often normal. However, if brand new leaves at the tips of branches are yellow, that indicates a problem.
Overall Yellowing vs Yellowing Between Veins
Also check the pattern of discoloration on the yellow leaves. Overall yellowing points to things like nutrient deficiencies, pests, diseases or stress. Interveinal chlorosis (yellowing between leaf veins) specifically indicates too high soil pH preventing nutrient absorption.
How to Fix Yellow Rhododendron Leaves
Confirm the cause before taking action to fix yellow rhododendron leaves. Here are tips for the most common issues:
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Adjust Soil pH
For interveinal chlorosis, use a soil pH tester to check for alkaline soil. Lower the pH with aluminum sulfate or elemental sulfur products. Target a pH of 4.5-5.5 for optimal nutrient absorption. -
Fertilize with Iron and Nitrogen
Uniform yellowing across whole leaves signals a nutrient deficiency. Use an acid fertilizer like Holly Tone or apply iron chelate. Fish emulsion and blood meal also provide fast nitrogen. -
Increase Shade
If leaves exposed to direct sun turn yellow, move the plant or provide shade. Dappled light is ideal. This reduces stress and prevents further sunscalding. -
Improve Drainage
Soggy soil leads to yellow leaves and wilting. Add organic matter to the soil or plant on a slope to improve drainage. Water carefully, avoiding standing puddles. -
Treat Pests and Diseases
For yellow splotches, spots or curling, inspect closely and treat any pests or fungal issues with appropriate organic sprays like neem oil or sulfur. Remove affected leaves. -
Deep Water in Drought
Drought stress also yellows leaves. Set a trickle hose to slowly deep water for a few hours 1-2 times per week during dry periods. Mulch also conserves moisture.
With the right diagnosis and care, you can get your yellow rhodiedendrons back to beautiful green in no time! Pay close attention to when and where leaves are yellowing and match solutions to the likely cause. A little TLC goes a long way for these flowering garden favorites.
Why Does My Rhododendron Have Yellow Leaves?
Before you begin, make sure that what you are seeing is not just leaf senescence – old leaves falling off at the end of their two or three year life. This happens just before winter or in summer drought. Yellow rhododendron leaves often represent the plant’s expression of dissatisfaction with its care. Rhodies are picky about the soil you plant them in and about how much water they like. If you see your rhododendron leaves turning yellow, review each and every element of the plant’s care. First, take a look at how well your soil drains. This shrub doesn’t do well in wet soil, and “wet feet” can cause leaves turning yellow on rhododendron. Give the plant a deep drink, then watch at how fast the water soaks into the soil. If your drainage is bad, transplant the shrub sooner rather than later to a location with well-drained soil. Test your soil’s acidity with a home pH tester. If your soil is alkaline, you’ve found one reason for rhododendron leaves turning yellow: a mineral deficiency causing chlorosis. These shrubs take up too much calcium and not enough iron in alkaline soils. Chlorosis is very likely when the yellowing is mostly between the veins of new leaves. Although it is possible to acidify the soil with sulfur, transplanting the shrub to a raised bed might be the best and quickest solution to rhododendron leaves turning yellow from chlorosis.
Another reason for yellow rhododendron leaves might be the way you planted the shrub. Rhododendrons should be planted with the root ball just at the soil surface. If you can’t feel the root ball in the soil, you have planted it too deeply. Replant at the proper level. This takes care of leaves turning yellow on rhododendron because of planting depth. Lack of water or food may also cause leaves turning yellow on rhododendron. You should give the plant fertilizer in late May to June. If you forgot this year, feed it now and, while you are at it, give it a good drink. If it perks up, you have found the problem. If none of these seem to describe your plant’s problem, ask yourself whether you have applied chemicals to its leaves lately. Misapplied chemicals can burn foliage, resulting in yellow rhododendron leaves.
RhodoDirect Explains Rhododendron Leaf Shedding – Unraveling the Mystery of Yellowing Leaves
FAQ
How do you treat yellow leaves on rhododendrons?
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1. Soil Testing:
- Test the soil’s pH to determine if it’s acidic enough for rhododendrons (ideally between 5.0 and 6.0).
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OregonLive.comhttps://www.oregonlive.comRhody leaves turning yellow? Use these tips to help them thriveFeb 13, 2021 — A: So many possibilities! First, rhododendrons are “understory” plants, meaning that, in nature, they live in the shade of tall trees, so planting t…
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Ashcombe Farm & Greenhouseshttps://ashcombe.comRhododendrons and AzaleasSOIL pH: Soil pH is important because it determines which nutrients a plant can take up from the soil. Rhododendrons and azaleas prefer acidic soil with pH 5-6.
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- If the soil is too alkaline, consider using sulfur to lower the pH or amend the soil with organic matter to help retain moisture.
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OregonLive.comhttps://www.oregonlive.comRhody leaves turning yellow? Use these tips to help them thriveFeb 13, 2021 — A: So many possibilities! First, rhododendrons are “understory” plants, meaning that, in nature, they live in the shade of tall trees, so planting t…
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Longfellow’s Garden Center – Centertown, MOhttps://longfellowsgarden.comYellowing in the Leaves of Shrubs and Trees – Longfellow’s Garden CenterApply a liquid fertilizer containing iron or Liquid Iron, though it may leave a rusty residue on the leaves. This is only a temporary solution. Adjusting the so…
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- Conduct a soil test for nutrient deficiencies, particularly nitrogen, iron, and magnesium, as they can cause yellowing.
- Test the soil’s pH to determine if it’s acidic enough for rhododendrons (ideally between 5.0 and 6.0).
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2. Fertilization:
- If nitrogen is low, apply a fertilizer specifically formulated for rhododendrons, such as Holly-tone or a balanced fertilizer.
- For iron deficiency, consider using a foliar spray or a fertilizer containing chelated iron.
- Magnesium deficiency can be addressed by applying a fertilizer containing magnesium or adding Epsom salts.
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Plantura Magazinhttps://plantura.gardenYellow leaves on rhododendrons: prevention and treatmentYellow leaves on rhododendrons indicate an iron deficiency. … If chlorosis is severe, foliar fertiliser should be applied. … If possible, only foliar fertil…
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Greg Apphttps://greg.appWhy Does My Rhododendron Have Yellow Leaves? – GregJun 18, 2024 — Nutrient Shortfalls Yellowing leaves on a Rhododendron can be a red flag for nutrient deficiencies. Nitrogen is essential for leaf growth, and its…
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- If nitrogen is low, apply a fertilizer specifically formulated for rhododendrons, such as Holly-tone or a balanced fertilizer.
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3. Watering and Planting:
- Ensure rhododendrons are watered regularly, especially during dry spells, but avoid overwatering that can lead to root rot.
- Plant rhododendrons at the correct depth, typically with the top of the root ball level with the soil surface.
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Gardening Know Howhttps://www.gardeningknowhow.comRhododendron Leaves Turning Yellow – Why Does My Rhododendron Have Yellow Leaves | Gardening Know How
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- Ensure good drainage to prevent waterlogging, which can also cause yellowing.
- Ensure rhododendrons are watered regularly, especially during dry spells, but avoid overwatering that can lead to root rot.
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4. Other Considerations:
- Evaluate the amount of sunlight the rhododendron receives, as excessive sun can lead to leaf burn.
- Check for pests like azalea lace bugs, which can cause yellowing and black spots on the underside of leaves.
- Consider transplanting the shrub to a location with better soil conditions or a raised bed if the soil is problematic.
- Evaluate the amount of sunlight the rhododendron receives, as excessive sun can lead to leaf burn.
What does overwatered rhododendron look like?
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Yellowing Leaves:Overwatering can lead to nutrient deficiencies, resulting in yellowing leaves.
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Droopy or Curled Leaves:Excess moisture can cause the leaves to droop, curl, or wilt, indicating the plant is not getting enough oxygen to its roots.
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Root Rot:If the roots are mushy and dark instead of firm and light-colored, root rot has likely developed, often caused by overwatering.
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Dieback of Branches:In advanced cases, the plant may experience dieback of branches, especially if the roots are severely damaged.
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Musty Smell:A musty or swampy smell can be a strong indicator of root rot, especially if it’s accompanied by wilting leaves.
What do I do if my plant leaves are turning yellow?
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Overwatering can lead to root rot, preventing the plant from absorbing nutrients. Signs include yellowing leaves, soggy soil, and potentially wilting.
- Solution: Allow the soil to dry out completely between waterings, ensure proper drainage, and use a well-draining potting mix.
- Solution: Allow the soil to dry out completely between waterings, ensure proper drainage, and use a well-draining potting mix.
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Underwatering can cause yellowing, brown edges, and crispy leaves.
- Solution: Water thoroughly when the soil feels dry to the touch, ensuring the water drains out of the pot’s drainage holes.
- Solution: Water thoroughly when the soil feels dry to the touch, ensuring the water drains out of the pot’s drainage holes.
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Yellowing leaves, especially with green veins, can indicate a lack of essential nutrients like nitrogen, magnesium, or iron.
- Solution: Use a balanced fertilizer specifically formulated for houseplants, following the instructions on the packaging.
- Solution: Use a balanced fertilizer specifically formulated for houseplants, following the instructions on the packaging.
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Lack of light can cause yellowing, especially on lower leaves.
- Solution: Move the plant to a brighter location or use supplemental grow lights.
- Solution: Move the plant to a brighter location or use supplemental grow lights.
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Pests like spider mites or mealybugs can weaken the plant and cause yellowing.
- Solution: Inspect the plant for pests and treat accordingly with appropriate insecticides or by isolating the plant from other healthy plants.
- Solution: Inspect the plant for pests and treat accordingly with appropriate insecticides or by isolating the plant from other healthy plants.