The single most common indoor plant problem I see in Australian homes through autumn and winter is overwatering. The watering schedule that kept plants happy in February is the same watering schedule that kills them in May, and the symptoms — droopy leaves, yellowing, dropping foliage — look enough like underwatering that the response is often to water more, which finishes the plant off.

Why winter is different

Most popular indoor plants are tropical or sub-tropical species that grow actively in warm conditions and slow down in cooler conditions. An Australian home in May, even with heating, is meaningfully cooler and drier than the same home in February. The plants respond by reducing their water uptake. Less photosynthesis, less transpiration, less water needed at the roots.

A pot that took a week to dry out in February might take two or three weeks in May. The same volume of water at the same interval is now too much, and the result is waterlogged roots and root rot.

The basic adjustment

The rough rule that works for most indoor plants in Australian conditions is to extend the watering interval to roughly half the summer frequency through autumn and winter, and to reduce the volume slightly when you do water.

For a plant that took 250ml of water every five days in February, that might mean 200ml every nine or ten days in May. Watering is not on a calendar — it is on the plant — but the calendar gives you the ballpark.

The finger test

The single best watering indicator for indoor plants is the finger test. Push a finger an inch or two into the top of the pot. If the soil is dry to that depth, water. If it is still damp, wait. The plant does not care what day of the week it is.

In winter the finger test will report “still damp” much longer than in summer. Trust the test. Skip the watering.

The signs of overwatering

The classic signs of overwatering are leaves that go soft and droop without recovering after watering, yellowing leaves starting from the bottom, brown leaf tips, and a smell from the soil that is heavier and more mushroom-like than the normal pleasant soil smell. The root system, if you remove the plant from the pot, looks dark and may smell bad.

The classic signs of underwatering are leaves that go droopy and crisp, leaves that look papery and dry, and soil that has pulled away from the sides of the pot. The root system looks dry but not rotten.

The two sets of symptoms look similar at the leaf level. The difference is in the soil and the roots.

The plants that need different rules

A few common indoor plants have different winter water needs.

Succulents and cacti want almost no water through winter. Every three to four weeks at most, and only enough to wet the soil lightly. Most succulent winter deaths are overwatering.

Ferns and air-loving tropicals (Boston ferns, maidenhair, calatheas) still want consistent moisture in winter but at a lower volume. The Australian winter humidity drop hurts them more than the temperature drop, so a regular mist or a humidity tray helps.

Orchids on a phalaenopsis schedule typically still want watering every seven to ten days in winter, but with less water at each watering.

Cuttings or recently-potted plants in active root development need more consistent watering even in winter. Once established, they shift to the slower pattern.

The other winter adjustments

Beyond watering, two other adjustments help indoor plants through the Australian winter. Move plants closer to light — the shorter day length and lower sun angle reduce the light most plants are getting. Avoid the cold spots — windowsills that get cold overnight, doorways with regular cold drafts, the back of a heater that swings between hot and cold air.

Most indoor plant winter losses are preventable with these few adjustments. The plants want less water, more light, and a stable temperature. Give them that and they make it to spring.