Why Are My Geranium Leaves Turning Yellow?

Yellow leaves on geraniums are one of the most common complaints from growers, yet the cause is rarely one single thing. Both hardy geraniums (cranesbills) and tender pelargoniums yellow for overlapping reasons — mostly cultural, occasionally disease-driven. Pinpointing the pattern of yellowing tells you most of what you need to know before you touch a single leaf.

Overwatering — the Most Frequent Culprit

Geraniums and pelargoniums hate wet feet. When compost stays soggy, roots suffocate and can no longer move nutrients to the leaves, so the oldest (lowest) leaves yellow first and may feel soft or translucent. Lift the pot — if it feels very heavy and the compost smells earthy-sour, you have drainage trouble. Fix it by letting the pot dry almost completely before watering again, and repot into a freely draining mix if the problem recurs. Never let plants sit in a full saucer for more than an hour.

Nutrient Deficiency

Nitrogen deficiency causes a pale, uniform yellowing that starts on the oldest leaves and works upward. Iron or magnesium shortages show up differently — interveinal chlorosis, where the veins stay green but the tissue between them turns yellow, usually on younger leaves first. In containers, nutrients wash out with every watering, so regular feeding with a balanced liquid fertiliser (or a high-potash tomato feed from midsummer onward) is essential. If you are growing in the ground and the soil is very acidic, lime the bed to improve nutrient availability before feeding.

Natural Leaf Shedding

Both cranesbills and pelargoniums routinely shed their lower leaves as they age. A small number of yellow-then-brown leaves at the base of an otherwise healthy, blooming plant is completely normal. Pick them off cleanly to maintain airflow and appearance; no other action is needed. If yellowing is restricted to one or two leaves per week on a vigorously growing plant, ageing is almost certainly the explanation.

Too Much Direct Hot Sun or Heat Stress

Pelargoniums enjoy sun but can scorch in intense, unbroken midday heat, especially against a south-facing wall. The leaves yellow or develop bleached patches in the centre and the edges curl inward. Move containers to a spot with morning sun and afternoon shade during a heatwave, and water early in the day so the root zone stays cool. Hardy geraniums growing in deep shade can also yellow from light starvation — move them to a brighter position or cut back overhanging plants.

Disease and Pest Damage

Fungal leaf spot and rust both cause yellowing, but they are accompanied by visible spots, rings, or powdery deposits. Whitefly and spider mite feeding causes a speckled yellowing that is more mottled than nutrient-linked pallor. Check the undersides of leaves carefully. Isolate affected plants, remove badly infected leaves, and treat with an appropriate fungicide or insecticide depending on the cause. Good airflow between plants is the best long-term prevention.