Rhododendron degronianum Yellow Leaves - Causes & Fixes

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Iron Chlorosis due to High Soil pH

Rhododendrons are acid-loving plants. If the soil pH rises above 5.5, iron becomes chemically unavailable to the plant, resulting in interveinal chlorosis (yellow leaves with green veins).

Very Common

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How to confirm: Check if the new growth is yellowing while the veins remain dark green.

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1 Apply an acidifying fertilizer specifically formulated for acid-loving plants to lower the soil pH and increase iron availability.

FoxFarm Happy Frog Acid Loving Plant Fertilizer

Organic

$22

In Stock

2 Check the soil pH regularly using a meter to ensure it remains within the ideal range of 4.5 to 5.5 for Rhododendrons.

YAMRON 4-in-1 Digital Soil Tester

Water Meters

$33

In Stock

3 Amend the soil with organic matter like sphagnum moss to help maintain acidity and improve moisture retention.

Better-Gro Sphagnum Moss 240ci

3.9 L • Sphagnum Moss

$5

In Stock

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Root Rot (Phytophthora)

Excessive moisture or poor drainage in the substrate leads to fungal pathogens attacking the root system, preventing water and nutrient transport to the foliage.

Very Common

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How to confirm: Gently lift the plant to check if the roots are dark, slimy, or have a foul odor.

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shopping_cart Recommended Products

1 Immediately inspect the roots for mushy, dark brown decay and prune away any dead or rotting sections using sterilized tools.

2 Repot the plant in a highly aerated, well-draining medium specifically formulated for acid-loving plants to prevent further moisture buildup.

FoxFarm Happy Frog Acid Loving Plant Fertilizer

Organic

$22

In Stock

3 Apply a fungicide treatment to the soil and foliage to combat the Phytophthora pathogen and prevent the spread of rot.

Bonide Captain Jack's Copper Fungicide 32 oz

0.9 L • 1 pcs • Organic

$12

In Stock

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Nitrogen Deficiency

A lack of available nitrogen in the growing medium causes older leaves to turn uniformly yellow before progressing to the new growth.

Common

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How to confirm: Observe if the yellowing starts on the oldest, bottom-most leaves first.

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shopping_cart Recommended Products

1 Apply a nitrogen-rich organic fertilizer to the soil to restore nutrient levels and promote green foliage growth.

FoxFarm Grow Big Liquid Plant Food 1 Quart

0.9 L • 1 pcs

$30

In Stock

2 Supplement with a specialized acid-loving plant fertilizer to ensure the soil pH remains low enough for nitrogen uptake.

FoxFarm Happy Frog Acid Loving Plant Fertilizer

Organic

$22

In Stock

3 Monitor soil moisture levels using a moisture meter to ensure the roots are not too wet, which can prevent nutrient absorption.

GROWIT Analog Soil Moisture Meter

Water Meters

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Water Stress (Drought)

As a species native to humid environments, significant periods of dry soil can cause the plant to shed chlorophyll and wilt as a defense mechanism.

Common

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How to confirm: Check the moisture level of the substrate several inches below the surface.

build How to fix it

shopping_cart Recommended Products

1 Check the soil moisture level immediately using a moisture meter to confirm if the root zone has reached a critical dry point.

GROWIT Soil Moisture Meter - Blue

Water Meters

$12

In Stock

2 Apply a deep, thorough watering to the base of the plant to rehydrate the root system, ensuring the soil remains consistently moist but not waterlogged.