Yellow leaves — chlorosis — are the single most common signal a plant sends, and also the most misread, because a dozen unrelated problems all end in the same colour. The trick to diagnosis is not the yellow itself but the pattern: which leaves yellowed (oldest, newest, or all at once), whether the veins stayed green, how fast it spread, and what the soil and roots are doing. Read those four things and the cause usually narrows to one or two possibilities.
The short answer
On houseplants the most common cause by far is overwatering — soggy soil starves roots of oxygen and they begin to rot, so leaves yellow even though the plant looks “thirsty.” The next most common causes are too little light, a nutrient shortage, and simple old-age leaf drop. Feel the soil and note which leaves are affected before you do anything — watering a plant that is already overwatered is the classic way to kill it.
How to identify the cause from the pattern
- Oldest, lowest leaves yellow first, evenly → nitrogen shortage, natural aging, or root/water stress.
- Newest leaves yellow with green veins (interveinal) → iron or manganese deficiency, usually a pH or root problem, not a lack of the nutrient in the soil.
- Older leaves yellow between the veins while veins stay green → magnesium shortage.
- All leaves pale and yellowing together → light shortage, cold stress, or serious root damage.
- Yellowing with wet soil → overwatering / root rot. With bone-dry soil → underwatering.
Water-related causes (check these first)
Overwatering is the number-one cause. Constantly wet soil drives the oxygen out of the root zone; roots suffocate and rot, and a rotted root system cannot move water or nutrients — so the plant yellows, wilts and drops leaves while sitting in wet soil. If the soil is wet and the lower leaves are yellowing and soft, treat it as root rot and read overwatering vs underwatering. Underwatering also yellows leaves, but they are usually dry and crisp and the soil has pulled away from the pot. Correct the watering rhythm using how to water houseplants, and if the pot drains poorly, fix that too — see improving soil drainage.
Root and soil causes
A root-bound plant — roots circling with almost no soil left — cannot hold water or nutrients and yellows steadily; it is time to repot. Wrong soil pH locks nutrients out even when they are present: iron becomes unavailable in alkaline soil, which is why acid-loving plants such as gardenias, azaleas, blueberries and citrus show yellow new leaves with green veins. Compacted or exhausted potting mix causes the same slow decline — refresh it and see choosing the right soil.
Light and temperature causes
Too little light forces a plant to shed its oldest leaves because it cannot sustain them; they yellow and drop from the bottom up. Move the plant brighter or add light — see light requirements for houseplants. A sudden move into fierce direct sun does the opposite, bleaching and yellowing the exposed leaves (see leaf scorch and sunburn). Cold drafts, heat stress and sudden temperature swings — a plant next to an air-conditioner, a cold window or a radiator — all trigger yellowing; keep plants away from those spots and protect tender ones from cold.
Nutrient causes
Because nitrogen and magnesium are mobile in the plant, a shortage shows first on the old leaves as the plant moves those nutrients to new growth. Iron and manganese are immobile, so their shortage shows on the new leaves. That mobility rule is the fastest way to tell a nitrogen problem (whole old leaves yellow) from an iron problem (young leaves yellow, veins green). Correct feeding with a balanced fertiliser usually fixes true deficiencies — see how and when to fertilize — but remember that most “deficiencies” in pots are really root or pH problems preventing uptake, so fix watering and pH before reaching for more fertiliser.
Pest and disease causes
Sap-sucking pests drain chlorophyll and cause fine yellow stippling or mottling; check leaf undersides for spider mites (fine webbing, dusty stippling) and mealybugs (white cottony clusters). Several fungal and bacterial leaf-spot diseases yellow the tissue around spots. Viruses cause yellow mosaic or ringspot patterns that no feeding will fix.
What to do now — and what not to do
Feel the soil first. Wet: stop watering, move to good light, and if roots are brown and mushy, unpot, trim the rot and repot into fresh, free-draining mix. Dry: water thoroughly and set a consistent schedule. Then check undersides for pests and consider light and feeding. Do not automatically add water to a yellowing plant — if it is overwatered you will make it worse — and do not pile on fertiliser hoping to “green it up,” which burns stressed roots.
Recovery, prevention and when it is normal
Yellow leaves rarely turn green again; the sign of recovery is healthy new growth, so judge success by the newest leaves, not the old ones. Remove badly yellowed leaves for appearance and to reduce disease. Prevent recurrence with the right pot and drainage, watering to the plant’s need rather than a fixed calendar, suitable light, and occasional balanced feeding in the growing season. Finally, a few yellow lower leaves are completely normal: plants routinely shed their oldest leaves as they grow, and many shed some foliage after being moved, repotted or brought indoors for winter. Widespread or rapid yellowing is what needs action.
Plant-group exceptions
Acid-lovers (gardenia, azalea, blueberry, citrus) yellow from iron lockout in hard water or alkaline mix — use rainwater and an ericaceous or acidic feed. Succulents that yellow and go translucent are almost always overwatered. Calatheas and marantas yellow from tap-water minerals and dry air as readily as from watering faults.
For a full breakdown of which nutrient causes which leaf pattern, see nutrient deficiency in plants.
Related plant problems
◀ Back to the Plant Problems hub to diagnose by symptom, pest or disease.
Leaves curling rather than yellowing? See why plant leaves curl — heat, pests, virus or herbicide stress.
- Why plant leaves drop
- Brown leaf tips and edges
- Wilting and drooping
- Leaf scorch and sunburn
- Transplant shock
- Leggy growth (etiolation)