Why does my ZZ plant have leaves falling off?

On a ZZ plant this is leaflets yellowing and falling, or whole stems dropping their leaves and going bare, sometimes after a cold night. The loss is often worst on the side of the plant nearest the window, and the stems that are left can look sparse.

The most likely cause is cold. The entry says it is usually a room below about 10 degrees, or a draught from a winter window. This is a plant from the warm lands of eastern and southern Africa, and the Royal Horticultural Society advises protecting it from extreme cold and draughts. A ZZ that has stood on a windowsill behind a closed curtain on a winter night can be far colder than the room.

To confirm it in a minute, think about where the plant stood and for how long. A cold windowsill, a spot near an outside door that is opened, or a room that is unheated in winter points to cold. A thermometer beside the plant for a night settles it. Also push a finger deep into the compost. A ZZ in cold, wet compost is at risk of rot, and that can drop leaves too.

Two other causes are worth ruling out. A recent move to a different spot, or a hot blast from a radiator or vent, causes leaf drop on plants that have no other fault. And watering at either extreme does it, though a ZZ is much more tolerant of dry compost than of wet.

The rhizomes underground are the plant's reserve, so a plant that has shed most of its stems is not necessarily dead. Check that a rhizome is firm. The recovery is slow: new stems come up in the next growing season, spring to early summer, not within weeks, and the plant will look thin until they do.

What this plant wants

The fix

Move it somewhere warmer and water less until spring. It regrows from the rhizomes when the temperature comes back up.

Read on

Leaves falling off

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

ZZ plant 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.