Diagnostic sheets · Leaf
Yellow leaves: how to tell normal ageing from rot in five minutes
Yellowing is the single most common houseplant complaint and it covers at least six unrelated problems. The fastest way to separate them is not to look at the leaf but at three things: how many leaves are affected, whether the veins stayed green, and whether the mix is wet.
| Symptom | Yellowing leavesLeaf |
|---|---|
| Likely causes listed | 6 |
| Confusable conditions | 3 |
| Remedies listed | 6 |
listLikely causes
- Normal ageing of the oldest leaf: one leaf at a time, from the bottom, uniform yellow with no spots, over two to three weeks.
- Overwatering: several leaves yellowing at once, lower leaves first, with soft or mushy stems and a wet-smelling mix.
- Nitrogen deficiency: uniform pale yellow across the whole plant including new growth, with a general loss of vigour.
- Iron or magnesium deficiency: yellow between the veins while the veins stay green (interveinal chlorosis), usually on new growth for iron and old growth for magnesium.
- Sudden cold: yellowing plus a water-soaked look after a plant has been next to a window during a cold night.
- Root constriction: a plant that has been in the same pot for years and is now yellowing slowly despite good care.
listWhat to do
- Identify whether it is one leaf or many. One bottom leaf every few weeks is normal and requires nothing.
- If many leaves are yellow and the mix is wet, stop watering entirely and check the drainage hole. Do not water again until the top 3-4 cm is dry.
- Turn the pot out and look at the roots. Firm white or tan roots are healthy; brown, soft, or foul-smelling roots mean rot. Cut the rotten roots off with clean scissors.
- If the plant is otherwise healthy, repot into fresh free-draining mix in a pot no more than 3 cm wider.
- For pale interveinal yellowing, feed with a balanced liquid fertiliser at half strength and check the pH. In very alkaline tap water, iron becomes unavailable even when it is present in the mix.
- Hold off on feeding a plant that is yellowing from overwatering. Fertiliser on damaged roots makes it worse.
differentialConfusable conditions
| Variegation | Some cultivars have yellow or cream leaf margins or centres by design. Check whether the colour has been there since the leaf opened. |
|---|---|
| Mosaic virus | Yellow mottling in irregular patches that cross the veins, on a plant whose growth is stunted. Not treatable; destroy the plant. |
| Spider mite damage | Fine pale stippling that reads as yellow from a distance. Look for webbing and mites on the leaf undersides. |
presentationWhat you are seeing
- One or more leaves losing chlorophyll and turning uniformly pale yellow, sometimes with a soft brown base where the petiole joins the stem, sometimes staying firm and yellow in place.
- The affected leaves may be only at the bottom, only at the top, only between the veins, or scattered at random.
aetiologyWhy it happens
- Ageing: the plant is withdrawing nutrients from an old leaf it no longer needs. This is a one-leaf-at-a-time event from the bottom, and it is not a problem at all.
- Overwatering: roots deprived of oxygen stop functioning, and the plant cannot move water or nutrients through them. The oldest leaves yellow first because the plant sacrifices them first.
- Nutrient deficiency: nitrogen produces uniform pale yellow across the whole plant; iron produces yellow between the veins with green veins intact; magnesium produces the reverse pattern on older leaves.
- Cold: cell damage from low temperature makes the leaf look water-soaked before it yellows, and the pattern follows the shape of the window or the draught.
managementWhat to do
- Count the affected leaves and note where they are on the plant.
- Check the mix with a finger or a moisture meter at 4 cm depth. Wet mix plus yellow lower leaves is overwatering until proven otherwise.
- If the plant has been in the same pot for more than two years with no feeding, feed at half strength and observe for three weeks.
- If the yellowing is interveinal on new growth, the cause is almost always iron at high pH, and repotting into fresh slightly acidic mix fixes it faster than feeding.
- Do not remove a yellow leaf while it is still attached and firm unless it has gone fully brown. The plant is still reclaiming nutrients from it.
The three-question diagnostic
Question one: how many leaves? One leaf at a time, from the bottom, on a plant that otherwise looks well, is ageing. Several leaves at once across different parts of the plant is a systemic problem.
Question two: are the veins green? If the leaf is yellow with green veins still visible, it is a nutrient problem — chlorosis — not a watering problem. If the leaf is uniformly yellow with no pattern, it is ageing, light, or water.
Question three: is the mix wet? Water 4 cm down. A wet mix plus yellow lower leaves plus soft stems is overwatering and it needs immediate action. A dry mix plus yellow lower leaves on an old plant is more likely to be normal ageing or root constriction.
- One leaf, bottom, plant otherwise fine: ageing, do nothing
- Uniform yellow, whole plant, pale: nitrogen deficiency
- Yellow between green veins, new leaves: iron deficiency
- Yellow between green veins, old leaves: magnesium deficiency
- Many leaves, wet mix, soft stems: overwatering — stop water now
- Yellow following a window shape after a cold night: cold damage
Why overwatering makes the oldest leaves yellow first
A plant that cannot take up water through damaged roots still needs water, so it pulls water out of its own leaves. It begins with the leaves that cost the least to lose — the oldest ones, which are in the shade of newer growth and contribute least to the plant's energy budget.
This is why the overwatering signal is always at the bottom. If you see a bottom leaf yellow and the stem base feels soft, stop watering and check the roots immediately. Rot in a 15 cm pot can go from the first yellow leaf to a dead plant in ten days.
Fixing chlorosis properly
Chlorosis is yellowing between green veins, and it most often means iron at a pH the plant cannot extract it from. Tap water above pH 7 gradually raises the mix pH, and above about 6.5 iron becomes insoluble, sitting in the pot but unavailable.
The fast fix is repotting into fresh, slightly acidic mix — coir or peat-based, with a little bark. The slow fix is a chelated iron feed, which works but takes three to four weeks to show in new leaves. Do not use iron sulphate directly, which is unavailable at high pH and can burn the roots.
Magnesium deficiency produces the same pattern but appears on older leaves first, because magnesium is mobile in the plant and moves to new growth. Epsom salts at one teaspoon per litre, once, is usually enough to correct it.
Plants this applies to
| Golden pothos: the low-light plant that still needs some light | Epipremnum aureum is the most forgiving houseplant in the aroid family and the most misused. It genuinely tolerates 200 lx, which is why it survives… |
|---|---|
| Peace lily: the plant that tells you when it is thirsty | Spathiphyllum is unusual among houseplants in that it signals drought loudly and recovers from it completely. It is also one of the few that flowers… |
| Fiddle-leaf fig: why it drops leaves every time you move it | Ficus lyrata is sold as a statement plant and kept, usually, in conditions it cannot tolerate. It needs more light than almost any other common… |
| Calathea orbifolia: a plant that is honest about humidity | Goeppertia orbifolia — still sold as Calathea — has the largest leaves of the common prayer plants, and the least tolerance for dry air. It is not a… |
| Spider plant: brown tips, and why this one really is the water | Chlorophytum comosum is the plant most often recommended for beginners and the one most often described as having brown tips from low humidity. For… |
Troubleshooting
Should I pull the yellow leaf off?
My plant has three yellow leaves at once after I overwatered it last week. Is it too late?
Can too much light cause yellow leaves?
CaveatCultivation guidance only, not a plant pathology diagnosis: the same symptom usually has several unrelated causes, so treat the least invasive cause first and change one variable at a time. If a plant is valuable to you, isolate it before treating.
Published2026-08-23 ·