Lactuca sativa Yellow Leaves - Causes & Fixes

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Nitrogen Deficiency

Nitrogen is highly mobile in lettuce; when levels are low, the plant moves nitrogen from older leaves to new growth. This results in characteristic uniform yellowing (chlorosis) of the older, bottom leaves first.

Very Common

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How to confirm: Observe if the yellowing starts at the base of the plant and progresses upward toward the crown.

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shopping_cart Recommended Products

1 Apply a nitrogen-rich liquid fertilizer to provide immediate nutrient uptake for the developing leaves.

FoxFarm Grow Big Liquid Plant Food 1 Quart

0.9 L • 1 pcs

$30

In Stock

2 Supplement the soil with a nitrogen-heavy organic amendment like blood meal to ensure long-term nutrient availability.

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

Organic Fertilizer

$40

Out of Stock

3 Monitor soil moisture levels to ensure nitrogen is being effectively transported to the roots.

GROWIT Soil Moisture Meter - Blue

Water Meters

$12

In Stock

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Overwatering and Root Hypoxia

Lettuce has a shallow root system that is highly sensitive to waterlogged soil. Excess moisture displaces oxygen in the soil, leading to root suffocation and a loss of chlorophyll production.

Very Common

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How to confirm: Stick your finger deep into the growing medium to check if it feels saturated or muddy.

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shopping_cart Recommended Products

1 Immediately stop watering and allow the soil to dry out significantly to restore oxygen levels to the root zone.

GROWIT Soil Moisture Meter SMM-V3

Water Meters

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2 Repot the lettuce in a well-draining medium, incorporating perlite to improve aeration and prevent future waterlogging.

3 Ensure the plant is in a container with adequate drainage holes and use a saucer to catch excess water, but do not let the pot sit in standing water.

Bleuhome 10" Plant Saucer 6-Pack Black

Pot Saucers

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Iron Chlorosis

High soil pH (alkaline conditions) can lock iron away from lettuce roots. This causes interveinal chlorosis, where leaves turn yellow but the veins remain dark green.

Common

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How to confirm: Check if the newest leaves at the center of the rosette are turning yellow while veins stay green.

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shopping_cart Recommended Products

1 Lower the soil pH to a more acidic range (5.5–6.5) to unlock iron availability, which can be achieved by using acidifying amendments or specialized fertilizers.

FoxFarm Happy Frog Acid Loving Plant Fertilizer

Organic

$22

In Stock

2 Apply a chelated iron supplement or a balanced liquid fertilizer to provide immediate iron uptake to the plant.

FoxFarm Grow Big Liquid Plant Food 1 Quart

0.9 L • 1 pcs

$30

In Stock

3 Monitor soil moisture levels regularly using a moisture meter to ensure consistent hydration, as extreme wet or dry cycles can exacerbate nutrient lockout.

GROWIT Soil Moisture Meter - Blue

Water Meters

$12

In Stock

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Temperature Stress (Heat Stress)

Lettuce is a cool-season crop; exposure to temperatures above 25°C (77°F) can trigger physiological stress. This often manifests as rapid yellowing and eventual bolting.

Common

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How to confirm: Monitor local ambient temperatures and check if the plant center looks elongated or bitter.

build How to fix it

shopping_cart Recommended Products

1 Relocate the lettuce to a cooler, shaded area or use a shade cloth to reduce direct heat exposure and prevent further yellowing.

2 Increase watering frequency to maintain consistent soil moisture and cool the root zone, using a tool like the GROWIT Soil Water Monitor to ensure the soil doesn't dry out.

GROWIT Soil Moisture Meter - Blue

Water Meters

$12

In Stock

3 Apply a light mulch around the base of the plants to insulate the soil and keep temperatures stable.