Geraniums are popular for their vibrant blooms and relatively easy care. However, yellow or red leaves often signal an underlying issue with the plant’s environment or health. Understanding these discolorations is the first step toward restoring your geraniums. This article explores the common causes of yellow and red leaves on geraniums and provides guidance on how to address them.
Why Geranium Leaves Turn Yellow or Red
Watering Issues
Geraniums are sensitive to both too much and too little water. Overwatering frequently causes yellowing leaves, often with wilting even in wet soil. Excess water deprives roots of oxygen, leading to root rot. Mold or algae may also appear on the soil surface.
Conversely, underwatering also causes yellowing, starting with leaf edges and tips. Severe cases result in brown, brittle leaves. Geraniums require consistent moisture; water when the top 1 to 2 inches of soil feel dry.
Nutrient Deficiencies
A lack of specific nutrients significantly impacts leaf color. Nitrogen deficiency causes general yellowing, beginning with older, lower leaves, and may stunt plant growth. Apply a balanced fertilizer containing nitrogen to address this.
Phosphorus deficiency results in reddish or purplish tints on leaves, particularly older, lower ones, which may eventually turn brown. Magnesium deficiency appears as yellowing between leaf veins, starting at the margins. Iron deficiency causes yellowing of new leaves while veins remain green. Applying a balanced fertilizer with these micronutrients corrects these deficiencies.
Temperature Stress
Extreme temperatures can cause geranium leaves to change color. Cold conditions, below 50°F (10°C), can cause reddish or purplish tints on older leaves, especially along the edges, and yellowing. Brief cold snaps can also lead to yellow leaves. Geraniums thrive with daytime temperatures around 70-75°F (21-24°C) and nighttime temperatures around 60-65°F (15-18°C).
Conversely, hot temperatures, above 85°F (29°C), can cause yellowing, scorch marks, and wilting. While geraniums prefer warmth, excessive heat is detrimental. Provide afternoon shade in hot climates to protect plants.
Light Problems
Geraniums are sun-loving plants that need ample light to thrive. Insufficient light leads to pale yellowing of leaves and leggy growth as the plant stretches for light. They require at least six hours of direct sunlight daily for healthy growth and vibrant color.
Too much direct sunlight, particularly intense midday sun in hot climates, can cause scorching, yellowing, or browning of leaves. Some varieties may develop a reddish hue as a protective response to high light intensity. If plants show signs of scorching, move them to a location with partial afternoon shade.
Pests and Diseases
Pests and diseases also contribute to leaf discoloration. Common pests like spider mites and aphids feed on plant sap, leading to yellowing or mottled leaves. Inspect the undersides of leaves for tiny insects or sticky residue to identify pest issues.
Fungal diseases such as Alternaria leaf spot cause dark brown, irregularly shaped spots, with a yellow halo, primarily on lower leaves. Botrytis blight, or gray mold, appears as brown, water-soaked spots on leaves and petals in cool, damp conditions. Bacterial blight, caused by Xanthomonas hortorum, results in small, water-soaked spots or V-shaped yellow to brown lesions on leaves, often leading to wilting. Discard infected plants to prevent spread.
Aging and Natural Cycle
It is normal for older, lower geranium leaves to yellow and eventually drop off. This is a natural part of the plant’s life cycle as it sheds older foliage to focus energy on new growth. This natural shedding is not a cause for concern unless widespread yellowing occurs across the entire plant.
Preventing Yellow and Red Geranium Leaves
Proactive care maintains healthy geraniums and prevents leaf discoloration. Plant geraniums in well-draining soil, as good drainage prevents root rot. For container plants, use pots with adequate drainage holes. Water consistently, allowing the top soil layer to dry between waterings.
Regular fertilization during the growing season provides necessary nutrients for robust growth and vibrant foliage. A balanced slow-release fertilizer applied in spring works for garden soil. For potted plants, apply liquid fertilizers every two to three weeks. Ensure adequate air circulation to prevent fungal diseases. Regularly inspect plants for pests or diseases to address issues promptly.
When to Seek Further Help
If your geraniums continue to exhibit yellowing or reddening leaves despite consistent troubleshooting, the problem might be more complex. If symptoms are severe, rapidly spreading, or accompanied by unusual growths or widespread wilting, seek expert advice. Consulting a local nursery, university extension office, or professional plant care specialist can provide a more accurate diagnosis and tailored solutions for persistent health issues.