Why does my calathea have yellow lower leaves?

On a calathea this is an older leaf, low and on the outside of the clump, turning yellow, often from the edge in, while the leaves higher up stay a good green with their silver bands.

The most likely cause, as the entry says, is waterlogged compost, or cold. This plant is kept lightly moist, so it is watered often, about every 5 days in the growing season and 9 in winter, and that is exactly why it is easy to overdo. A pot much larger than the root ball holds wet compost the plant cannot use, which brings on the yellow lower leaves that look like overwatering because that is exactly what they are. The NC State plant toolbox says overwatering can cause root rot.

To confirm it in a minute, push a finger into the compost. It should be just dry at the surface, and if it is wet down to the second knuckle days after watering, the pot is the cause. Lift the pot, and check the saucer and any decorative cover, because the RHS says to empty any water that collects there. In winter the RHS also warns of oedema, which shows as patchy, water soaked areas on the leaves when the compost is too wet.

Two other causes are worth ruling out. Cold: the entry says to keep the room above 16 degrees, and the RHS gives 16 to 21 degrees. A cold sill or a draught is the other cause the entry gives. And age, where one old leaf yellows while new ones keep opening, is normal.

A yellow leaf never turns green again, so judge the recovery by the next new leaf. Once the roots can breathe the next leaves should open clean. That takes a few weeks in the growing season and longer in winter. If the roots have rotted, the plant needs longer.

What this plant wants

The fix

Check that the pot drains and that the room stays above 16 degrees. Let the surface dry slightly before watering again.

Read on

Yellow leaves at the bottom of the plant

The same sign on any plant, with the causes in the order they are likely.

Calathea care

Light, water, feeding, repotting and the rest of the entry.

Check it in the diagnoser

Opens with the plant, the part and the sign already chosen.