Why are my houseplant's leaves turning yellow?

Which leaves are turning yellow?

University of Maryland Extension says the pattern and progression of symptoms help diagnose the cause.

One lower leaf on a mature plant. The Royal Horticultural Society (RHS) calls this normal.

From the bottom up. On a dry plant, the older leaves near the soil tend to yellow and drop first, the RHS says. Low light can also yellow lower leaves.

Old and new leaves together. The RHS lists this as a sign of overwatering.

Upper leaves, or yellow between green veins. On lime-hating plants such as gardenia, the RHS links this to iron or manganese being unavailable, often after long use of hard tap water. Yellow between the veins can also signal low magnesium, Washington State University says.

Yellow leaves: what to notice before choosing a treatment

What you notice	What to check	A useful next step
One older, lower leaf	Watch the rest of the plant. Occasional older-leaf loss can be normal.	Note the date and check whether more leaves follow.
Mix still wet; water in the outer pot	Watering and drainage. A yellow leaf is not a signal to add more water.	Empty collected water and compare moisture with your plant’s needs.
Dry mix; leaves also drooping	Moisture below the surface and the plant’s usual care needs.	Water if the mix and the plant’s needs call for it.
Yellowing after a move or weather change	A new light level, strong sun, heater or cold draft.	Record what changed and adjust unsuitable conditions.
Spots, webbing or visible insects	Both sides of the leaves and the stems.	If pests are suspected, separate the plant while you identify the problem.

These are checks, not diagnoses. More than one cause can produce the same symptoms. Based on the RHS and University of Maryland guidance cited in this section.

If you find fine webbing or pale speckles, check for spider mites.

Sources: Yellowing Leaves on Indoor Plants; Leaf damage on houseplants; How to help a poorly houseplant; Miracle, myth...or marketing: Epsom salts.

What should you check first?

1. Potting mix. Push a finger about two inches in. If the mix is dry, the plant probably needs water. If it is still wet, hold off.
2. Pot base and roots. Lift the plant out and tip away any water in the base. Dark, soft or brittle roots are a sign of root trouble.
3. Light. Too much shade can turn leaves yellow, and so can strong midday sun.
4. Cold and drafts. Air from doors, windows or ducts can make leaves yellow and drop, whether warm or cold, Iowa State University Extension says.
5. Food. Under-fertilized plants often yellow, Iowa State says. The RHS advises getting light, water and potting mix right before you add feed.
6. Pests. Damage that looks like insects or disease often comes from the plant's environment, University of Maryland Extension notes, so confirm pests before you treat. If you use a product, choose one labeled for that pest and use.

If yellow leaves are one of several symptoms, try what's wrong with my plant. If you still cannot find the cause, take photos and notes on recent changes to a local nursery or extension service.

Sources: Watering Indoor Plants; How to help a poorly houseplant; Leaf damage on houseplants; What causes leaves on my houseplant to turn yellow or brown and drop off?; Yellowing Leaves on Indoor Plants.

Is it too much water or too little?

University of Maryland Extension names overwatering as the top reason indoor plants fail, and the RHS warns that overwatering also causes wilting, so a droopy plant is not proof of thirst.

Wet mix, water in the pot base, or dark, mushy roots point to too much water. Dry mix and wilted leaves with crispy brown edges point to too little.

If the signs conflict, use this overwatered or underwatered tie-breaker. For routine care, see how often to water houseplants.

Sources: Yellowing Leaves on Indoor Plants; How to help a poorly houseplant.

Why are leaves turning yellow after repotting or a move?

Yellow leaves or leaf drop after repotting are normal, Montana State University Extension says. It advises indirect light for a few days and no fertilizer for at least two weeks, so roots can regrow. A pot that is too large can also cause yellowing, the RHS says.

After a move, Iowa State says a sudden change in light can cause leaf drop, so change light gradually. Cold during transport can also make leaves yellow and drop. We found no extension or RHS figure for how long recovery takes, so keep checking if the yellowing spreads.

Sources: Ask Steward: How do I repot a houseplant?; Leaf damage on houseplants; What causes leaves on my houseplant to turn yellow or brown and drop off?.