Why is my coleus turning yellow?

The 4 most likely causes

The cause of coleus yellow leaves usually narrows to one of the items below, ranked by how often we see each in Growli's diagnostic chats. Work down the list — most readers find their answer in the top two.

1. Overwatering or poor drainage (Most likely)
   In most homes overwatering is more often a drainage problem than a frequency problem. Coleus needs a pot with a drainage hole, a chunky free-draining mix, and a watering rhythm of water when the surface dries — it wilts fast and recovers fast. Soggy soil drowns the roots and the first symptom you see above ground is yellowing or wilting foliage.
2. Wrong light level (Likely)
   Coleus is a high-light plant and quickly turns leggy, pale, or stalled in low light. Move it within a metre of a south or east-facing window, or supplement with a grow light. It wants bright light; morning sun deepens the colour.
3. Nutrient deficiency (nitrogen or iron) (Possible)
   If coleus has not been repotted or fed in a year or more, the older leaves can yellow uniformly while the newest growth stays green — a classic sign of nitrogen depletion. Yellow leaves with green veins on new growth point to iron or manganese deficiency. A balanced liquid feed during the growing season usually resolves both.
4. Underwatering or letting it dry too long (Possible)
   Coleus is a thirsty plant that wilts dramatically when it dries out. If the leaves are limp and the soil pulls away from the pot edge, it has gone too long between waterings. Soak the rootball thoroughly until water runs out the drainage hole.

Why coleus in particular

A tender tropical of Southeast Asian forests grown for its foliage, coleus is a soft, fast herb in the mint family, and it yellows readily when unhappy. Cold is a frequent trigger, since this frost-tender plant sulks and yellows in a chilly room or draught, as are soggy roots and hungry soil in a fast grower that feeds heavily. Some lower-leaf yellowing is normal as vigorous stems shade their own bases. Even, widespread yellowing usually points to cold or overwatering rather than age.

Normal turnover, or real trouble?

A fast, soft mint-family plant sheds a lower leaf or two as its vigorous stems shade their own base, so a little yellowing low down on a leafy plant is ordinary. Read it as trouble when the yellowing is even and widespread, when it follows a chilly night or a draughty sill, or when it comes on soil that stays wet, since this tender tropical answers cold and sodden roots with wholesale paling.

How to diagnose in 60 seconds

Run these quick checks before you change anything — the right fix depends on what you find.

• Coleus wants water water when the surface dries — it wilts fast and recovers fast. Push a finger into the mix and hold it against that: still damp well before it is due, alongside the symptom, is the overwatering signature.
• Are the yellowing leaves the oldest ones at the base, or the newest at the tips? Old-leaf yellowing is usually water or nitrogen; new-leaf yellowing is usually iron or root damage.
• Look at the back of a yellow leaf with strong light — any speckling, webbing, or sticky residue? That points to pests, not water.
• Tip coleus out of its pot and look at the roots: firm and pale is healthy; brown, soft or sour-smelling is rot, which is the real cause behind most of these symptoms.

The fix — step by step

First rule out cold, the fix others miss: move the plant off any draughty or chilled sill into a steadily warm room, away from cold glass and out of frost's reach, since it starts to suffer once the air drops much below room warmth. Then check the soil; if it is wet, ease off watering and let it dry before the next drink. A hungry grower may want a weak feed once warm and dry.

This is the recovery sequence Growli walks users through for coleus with yellow leaves. Work through the steps in order; skipping ahead is the most common reason a plant fails to bounce back.

1. Stop watering and check the roots. Don't add more water yet. Unpot coleus and look at the rootball — firm white roots mean you have time; brown mushy roots mean you need to act today.
2. Trim damaged roots and yellow leaves. Cut off any soft brown roots with clean scissors. Remove fully yellow leaves at the base — they won't green back up. Leave half-yellow leaves alone for now; the plant is still pulling nutrients out of them.
3. Repot into fresh dry mix. Repot into fresh, well-draining mix in a pot one size up. For coleus, pick a spot with bright light; morning sun deepens the colour.
4. Reset the watering rhythm. Water deeply once, then wait. For coleus, that means water when the surface dries — it wilts fast and recovers fast. Use a finger or a moisture meter — never a calendar.
5. Resume feeding only after recovery. A stressed plant cannot use fertiliser and the salts will worsen the damage. Wait for at least one round of healthy new growth (4-6 weeks) before resuming a half-strength liquid feed during the growing season.

When this can't be saved

Most cases of coleus yellow leaves are recoverable, but a few red flags point to a plant that has gone past the point of return. If you spot any of these, consider propagating a clean cutting and starting over.

• Every leaf has yellowed simultaneously and the stem feels soft at the base — root rot has likely consumed the plant.
• New leaves emerge yellow and crispy and never green up — the growing tip is damaged.
• The soil smells sour or sulphurous even after a thorough drying period.

Prevention

For coleus, the single biggest preventative is matching its native rhythm: water when the surface dries — it wilts fast and recovers fast, bright light; morning sun deepens the colour, and a free-draining pot with a working drainage hole. Group coleus with plants of similar needs so you can water them as a batch rather than guessing per-pot. Set a calendar reminder to feed during the growing season but never feed a sick or freshly-repotted plant — wait for healthy new growth first.

Common questions

Related guides

• What's wrong with my plant? — the diagnosis apps compared
• Is coleus toxic to cats and dogs? — toxic to pets, per the ASPCA
• How often to water coleus — the watering brief
• When to repot coleus — pot size and timing
• Yellow leaves on plants — the full diagnostic guide across species
• What's wrong with my plant? — Growli's flagship diagnosis index
• Coleus — curling leaves
• Coleus — drooping
• Coleus — brown spots
• Monstera — yellow leaves