Why Are My Plant Leaves Turning Yellow? 7 Causes & Fixes
Yellow leaves are the most common distress signal plants send. Here's how to diagnose exactly what's wrong and fix it fast.
Reading Your Plant’s Distress Signals
Yellow leaves are one of the most common plant complaints, and also one of the most misdiagnosed. The mistake most people make is assuming the cause immediately — usually over-watering — when in reality there are seven distinct causes, each requiring a different fix.
Cause 1: Over-Watering (Most Common)
Over-watering is the number one plant killer. Symptoms: yellow leaves that feel soft and mushy, soggy soil, possibly mould on the soil surface, and sometimes a smell of rot. Fix: stop watering immediately, check the roots (healthy roots are white/cream; rotten roots are brown/black and mushy). If root rot is present, remove affected roots, repot into fresh compost with added perlite, and water only when the top 3–4cm of soil is dry.
Cause 2: Under-Watering
Under-watered plants have yellowing leaves too, but they feel crispy and dry rather than soft. The soil will be completely dry and pulling away from the pot sides. Fix: water thoroughly until it drains from the bottom, then wait. Don’t compensate by over-watering — let the plant recover gradually.
Cause 3: Nutrient Deficiency
Nitrogen deficiency causes uniform yellowing starting on older (lower) leaves. Iron or magnesium deficiency shows as yellowing between leaf veins while the veins stay green — called chlorosis. Fix: use a balanced liquid fertiliser for general deficiency; for chlorosis, use a feed containing chelated iron.
Cause 4: Too Little Light
Plants in insufficient light gradually lose their green colour as chlorophyll degrades. The yellowing tends to be uniform across the whole plant rather than concentrated in one area. Fix: move to a brighter spot or add a grow light. Recovery is slow but steady over 4–6 weeks.
Cause 5: Natural Ageing
If only the lowest, oldest leaves are yellowing while the rest of the plant looks healthy, this is completely normal. Plants shed old leaves to redirect energy to new growth. No action needed — simply remove yellow leaves to keep the plant looking tidy.
Cause 6: Root Bound
When a plant’s roots completely fill its pot, it can no longer absorb nutrients efficiently, leading to yellowing. Check by gently removing the plant — if roots are tightly circling the bottom or emerging from drainage holes, it’s time to repot into a container 2–3cm larger.
Cause 7: Pests
Spider mites, fungus gnats, and scale insects all cause yellowing leaves. Check the undersides of leaves (spider mites leave fine webbing), the soil surface (fungus gnats prefer moist compost), and stems (scale insects look like brown bumps). Treat with neem oil spray for an organic, effective solution.