Why are my plant leaves turning yellow?
Where the yellow shows up is the biggest clue. Pick what you see, and PlantWise narrows down the likely causes.
- Natural ageing. One or two bottom leaves yellowing slowly while new growth is healthy is normal: the plant moves nutrients out of old leaves.
- Overwatering. Soil stays wet for days, leaves go soft and yellow, sometimes with a musty smell. The most common cause in pots.
- Nitrogen shortage. Uniform pale yellow working up from the bottom, slow growth. Common in old potting mix and hungry vegetables.
- Magnesium shortage. Yellow between green veins on older leaves; tomatoes and peppers are prone.
Still unsure? Photograph the plant and use the plant doctor in “What’s wrong with it?” mode.
Chlorosis: why the pattern points to the cause
A leaf is green because it is packed with chlorophyll, the pigment that captures light. Building chlorophyll takes nitrogen and magnesium (it sits at the centre of every chlorophyll molecule), and iron, sulfur and manganese are needed to make it. When any of them runs short, new chlorophyll can’t be made and the leaf fades to the yellow carotenoids that were there all along.
Which leaves fade depends on whether the plant can move the nutrient. Mobile nutrients (nitrogen, magnesium, potassium) are pulled out of old leaves to feed new ones, so shortages show at the bottom first. Immobile ones (iron, sulfur, calcium, manganese) stay put, so the newest leaves go without.
A yellowing leaf is really a leaf dismantling its light-harvesting equipment. How that equipment turns light, water and air into sugar is exactly what ahaboo’s photosynthesis explainer lets you step through, narrated, piece by piece.
Overwatering causes similar yellowing for a different reason: roots in waterlogged soil suffocate and stop taking up nutrients, so the plant shows a nitrogen-like shortage even in rich soil.
Ask about your plant
Questions gardeners ask
Should I cut off yellow leaves?
Yes, once a leaf is mostly yellow it will not turn green again. Removing it tidies the plant and, if disease is involved, reduces spread. Fix the cause first, or new leaves will follow.
Can a yellow leaf turn green again?
Only if the yellowing is mild and caused by a nutrient shortage that you correct quickly. Leaves that are fully yellow have broken down their chlorophyll and will not recover.
What is chlorosis?
Chlorosis is yellowing caused by a lack of chlorophyll, the green pigment. Its pattern (old vs new leaves, whole leaf vs between veins) is the best clue to the cause.
Is Epsom salt good for yellow leaves?
Only when magnesium is actually short, which is less common than often claimed. Extension services such as Washington State University advise a soil test before adding it.