What Does it Mean When Leaves of Trees & Plants Turn Yellow?

Healthy green gardens are a pleasure to see. It can be troubling, though, when the leaves of garden plants and trees turn yellow prematurely. There are various reasons why plants lose their green coloring.

Disease

Some plant diseases cause yellow leaves, such as bacterial tip burn and leaf spot. These conditions are caused by harmful bacteria that cause the tips and margins of leaves to yellow. As these diseases progress, entire leaves yellow and drop. Rust is another disease that affects a wide variety of plants. It begins as white spots ringed in yellow and turns into a yellow powder on leaves. Eventually the foliage yellows and drops.

Nutrient Deficiency

Lack of sufficient nutrients causes plants and tree foliage to yellow. Nitrogen deficiency leads to an overall yellowing of older leaves; a magnesium shortage causes older leaves to yellow at the edges. Yellowing in younger leaves indicates a sulfur deficiency. Iron chlorosis is an iron deficiency that shows up as dark leaf veins surrounded by yellow. The condition is a sign that iron is unavailable to plants often because of overly high soil pH.

Pests

Pests such as the whitefly suck plant juices from foliage, which makes leaves yellow and dry.

References

• University of Minnesota Extension: Bacterial Leaf Diseases of Foliage Plants
• University of Arizona Cooperative Extension: Guide to Symptoms of Plant Nutrient Deficiencies
• University of Missouri Extension: Yellow Leaves, Iron Chlorosis
• University of Missouri Extension: Managing Whiteflies on Indoor and Outdoor Plants
• Alabama Cooperative Extension System: Plant Disease Notes-Rust of Garden Beans

Resources

• Purdue University Extension: Leaf Diseases