Post category: Heat Requirements


Heated rooms 


Coleus likes warm conditions


Although house plants need warmth for growth, the main concern is to provide conditions warm enough for healthy survival through winter. Many house plants come through winter in such bedraggled condition that they are thrown out. Because indoor temperatures are usually higher than outdoors, most of the plants used as house plants are native to warm climates.


Partly heated rooms



Busy lizzie is quite tolerant

Rooms that are heated for part of the day in winter are suitable for the majority of house plants. The temperature usually stays above 10° to 12° Celsius, and this is adequate for most house plants. Flowering house plants stay in flower longer in cool conditions.


Unheated rooms


Rooms that are not heated at all are suitable for only a limited range of house plants. On a cold night, temperature levels can fall to 5° Celsius in such rooms, and even close to freezing on occasion. These are harsh conditions for house plants and many types will lose condition.

Plants that can survive unheated rooms include geraniums, rubber plant, fatsia, ivy, silk oak, spider plant, mother of thousands, cacti and succulents, cyclamen, primula and cape primrose. Note, that behind the curtains of unheated rooms, plants might be exposed to frost.

Freezing conditions often occur in greenhouses and conservatories in winter, and since very few house plants can survive sub-zero temperatures, greenhouses are not suitable for overwintering house plants unless artificially heated.


Too much heat


Excessive heat is usually localised – caused by heaters or radiators. Any plant in direct contact with a heat source will be scorched and, even though the heater can be some distance away, brown marks could still appear on the leaves nearest to the source. If the air in the room is generally too warm and dry, brown edges often develop on the leaves over a period of time.


Too little heat


The main symptom of a problem with low temperatures is leaf drop. Plants drop leaves for several reasons – too much water, too little water, root damage, old age – but in winter, if leaves drop off suddenly, it is usually from cold. They are often still green when they fall. Some plants sacrifice part of the leaf, which later goes brown.

Many plants can adapt to low temperatures over a period, but even normally hardy plants can suffer if they get a sharp shock. This can be caused by a sudden move from a warm room to a cold one, or by draughts causing low temperatures at floor level.

Avoid sudden changes and, if plants are suffering move them for a while to a warm room to recover. A first sign of trouble, very often, is listless appearance – a slight droopy look – not quite wilting. Plants can tolerate cool conditions better if they are getting good light and are not over-watered.