Onion Yellow Stone F1 Yellow Leaves - Causes & Fixes

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Nitrogen Deficiency

Nitrogen is a mobile nutrient; when lacking, the plant moves it from older leaves to new growth, causing uniform yellowing starting with the lower leaves. This is common in onions during rapid bulb expansion phases.

Very Common

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How to confirm: Check if the yellowing started on the oldest, bottom-most leaves and move toward the center of the plant.

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1 Apply a nitrogen-rich liquid fertilizer to provide immediate nutrient uptake during the bulb expansion phase.

Back to the Roots Blood Meal & Gypsum (4 Pack)

Organic Fertilizer

$40

Out of Stock

2 Supplement the soil with an organic nitrogen source like blood meal to ensure long-term nutrient availability.

Back to the Roots Organic Blood Meal

Organic Fertilizer

$10

In Stock

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Overwatering and Poor Drainage

Excessive soil moisture deprives onion roots of oxygen, leading to root hypoxia. This prevents the uptake of nutrients, manifesting as yellowing or even translucent-looking leaf tissue.

Very Common

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How to confirm: Stick your finger 2 inches into the soil to check if it feels waterlogged or if there is standing water in the planting bed.

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1 Immediately reduce watering frequency and allow the top inch of soil to dry out completely before watering again to prevent further root hypoxia.

GROWIT Soil Moisture Meter SMM-V3

Water Meters

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2 Repot the onion in a container with superior drainage, such as a Root & Vessel cylinder pot, and use a well-draining medium amended with perlite to improve aeration.

3 Ensure the plant is not sitting in stagnant water by using a drainage saucer to catch excess moisture.

Bleuhome 10" Plant Saucer 6-Pack Black

Pot Saucers

$20

In Stock

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Allium Leaf Blight (Phytophthora)

This fungal pathogen causes yellowing and eventual necrotic lesions on onion leaves. It thrives in high-humidity environments and cool, wet conditions common in onion cultivation.

Common

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How to confirm: Look for water-soaked lesions or dark, purplish spots appearing on the yellowing leaf edges.

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1 Remove and destroy all infected plant material immediately to prevent the fungal pathogen from spreading to healthy onions.

2 Apply an organic fungicide to the remaining healthy plants to control the spread of the blight.

Bonide Captain Jack's Copper Fungicide 32 oz

0.9 L • 1 pcs • Organic

$12

In Stock

3 Improve air circulation and reduce humidity around the plants by spacing them properly and avoiding overhead watering.

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Temperature Stress (Heat or Frost)

Extreme temperature fluctuations can cause physiological stress in Yellow Stone onions. Sudden heat waves can cause leaves to bleach and turn yellow, while late spring frosts can damage the cellular structure.

Common

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How to confirm: Review recent local weather logs for any significant spikes in temperature or frost events following transplanting.

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1 Protect the onion from extreme temperature swings by using a frost cloth or mulch to insulate the soil and root zone.

2 Monitor soil moisture levels closely during heat waves to ensure the plant does not dehydrate, as heat stress is often compounded by drought.