Rhododendron micranthum 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 roots, causing interveinal yellowing in new leaves.

Very Common

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How to confirm: Check if the veins of the yellowing leaves remain dark green while the rest of the leaf turns pale yellow.

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shopping_cart Recommended Products

1 Apply an acidifying fertilizer to lower the soil pH and make iron more available to the roots.

FoxFarm Happy Frog Acid Loving Plant Fertilizer

Organic

$22

In Stock

2 Monitor the soil acidity levels regularly to ensure the pH remains in the ideal range of 4.5 to 5.5.

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 a low pH environment.

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 heavy soils 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 edge of the soil to check if the roots are dark, slimy, or have a foul odor.

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shopping_cart Recommended Products

1 Immediately reduce watering frequency and ensure the plant is in a well-draining environment to stop the spread of Phytophthora.

GROWIT Soil Moisture Meter SMM-V3

Water Meters

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2 Repot the plant into a highly aerated medium using an acid-loving substrate and add perlite to improve drainage and prevent future waterlogging.

3 Apply a fungicide treatment to protect the remaining healthy tissue from fungal pathogens.

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 nitrogen in the substrate causes older leaves to lose their green pigment first as the plant mobilizes nutrients to new growth.

Common

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

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shopping_cart Recommended Products

1 Apply a nitrogen-rich organic fertilizer to the soil to replenish the nutrient levels in the substrate.

FoxFarm Grow Big Liquid Plant Food 1 Quart

0.9 L • 1 pcs

$30

In Stock

2 Monitor the soil moisture levels using an analog meter to ensure the nitrogen-enriched water reaches the root zone effectively.

GROWIT Soil Moisture Meter - Blue

Water Meters

$12

In Stock

3 Ensure the plant is in an acidic environment by using a specialized fertilizer for acid-loving plants.

FoxFarm Happy Frog Acid Loving Plant Fertilizer

Organic

$22

In Stock

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Salt Accumulation

High levels of mineral salts from hard water or excessive synthetic fertilizers can burn the delicate root hairs of Ericaceous plants, leading to leaf yellowing.

Common

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How to confirm: Look for a white, crusty residue on the soil surface or the edges of the planting container.

build How to fix it

shopping_cart Recommended Products

1 Flush the soil thoroughly with large amounts of distilled or rainwater to leach out accumulated mineral salts from the root zone.

2 Repot the plant in fresh, acid-loving substrate specifically designed for Ericaceous plants to provide a clean growing medium.

FoxFarm Happy Frog Acid Loving Plant Fertilizer

Organic

$22

In Stock

3 Switch to a low-salt fertilizer and use a specialized acid-loving formula to maintain the proper pH for the Rhododendron.