Why are my Croton leaves turning yellow?

Where the yellow shows up matters

On a Croton (Codiaeum variegatum, in cultivars like Petra, Mammy, Gold Star, and Zanzibar), the location of the yellowing is the single most useful clue. Shock and watering problems hit the older, lower leaves first, so a Croton that yellows from the bottom up is usually telling you about its roots or its recent move. Light problems also work inside out, fading interior leaves toward plain green. By contrast, a single bottommost leaf going slowly yellow while everything above it stays vivid is just normal aging and needs nothing more than removal. Read the pattern before you change anything.

The most likely cause: a sudden change

A sudden change in environment is the top cause of yellow Croton leaves. Crotons resent disruption more than almost any common houseplant, and a move to a new room, a repotting, or even the trip home from the shop can trigger a wave of yellowing and leaf drop within days.

You can confirm it by the timing. If the yellowing started shortly after you moved, repotted, or bought the plant, shock is almost certainly the driver. The fix is patience and stability: leave the plant in one bright, warm spot above 60F (15C), resist the urge to keep adjusting it, and give it two to four weeks. New growth signals it has settled.

A worked example

Your Croton sits in a decorative pot with no drainage hole, you water it on a fixed weekly schedule, and the lower third of the leaves have gone yellow and slightly soft over the past two weeks. The pot feels heavy and the soil is still damp days after watering. Nothing about the spot has changed recently, so shock is unlikely. The heavy, wet pot and soft yellow lower leaves point to overwatering and the start of root rot. The fix is to repot into a container with drainage, let the soil dry to the top inch before watering again, and check the roots for brown mushy sections rather than to keep watering on schedule.

Other causes worth ruling out

These rank below environmental shock but often overlap with it.

• Overwatering. Soggy soil starves the roots of oxygen and rots them; lower leaves yellow, the pot feels heavy, and the soil stays wet for days. This is the most common houseplant killer, and the Missouri Botanical Garden explains how overwatering damages roots.
• Underwatering. Drought stress dries the plant out; the soil is bone dry, leaves yellow then curl, and the lower leaves go first.
• Cold drafts. Temperatures below 60F (15C) shock the foliage; yellowing follows a cold snap or appears near a chilly window or vent.
• Too little light. Dim spots dull the plant; colors fade toward plain green and leaves yellow and drop from the inside out.
• Natural aging. A single old lower leaf yellowing slowly is normal; only the bottommost leaf is affected and the rest look healthy.

How to fix it

1. Hold conditions steady. Pick one bright, warm spot and leave the plant there for several weeks instead of moving it around.
2. Check the soil. Feel the top inch. Water only when it is dry, then water thoroughly until it drains.
3. Improve drainage. Make sure the pot drains freely and empty any saucer so roots never sit in water.
4. Keep it warm. Hold the plant above 60 degrees Fahrenheit and away from cold drafts, open doors, and heating vents.
5. Give it bright light. Move it to a spot with several hours of bright light, including some gentle direct sun, to keep color.
6. Remove spent leaves. Cut fully yellow leaves at the base with clean scissors to redirect energy to new growth.
7. Raise humidity. Crotons prefer humidity above 40 percent, so group plants or use a humidity tray if your air is dry.