Indoor growing conditions can vary just as much as outdoors in a garden – the three key aspects to bear in mind are light, The concentration of water vapour in the atmosphere. This affects the rate at which plants transpire (lose water from their leaf pores), which in turn affects how much water their roots absorb from the soil. If air humidity is low, plants transpire quickly and become at risk of wilting if water is lost from the leaves faster than it can be absorbed by the roots. Different plants require different levels of humidity to thrive. Many tropical houseplants need high humidity and are best grown in a steamy bathroom, misted regularly or placed on a saucer of damp pebbles. In a greenhouse, humidity can be raised in hot weather by damping down (wetting) the floor or overhead misting.
Amount of light
Light levels are very important to plants, as is the type of light (full sun, bright indirect light and shade). Bear in mind that light will fluctuate across the day, and at different times of year. A spot with direct sun in summer will often cause leaf discoloration and scorching, unless the light is filtered by sheer curtains or blinds. In winter, that location may be a prime growing spot, when the sun is weaker and the days are shorter.
Many plants would struggle in locations set back from windows, where they get very little light. North-facing windowsills can be tricky too, especially in winter when day lengths are reduced.
Domestic lighting doesn’t provide suitable light for plant growth, although artificial grow lamps are widely available if you need to provide additional brightness. These can be expensive, both to buy and run, and aren’t ideal lighting for most homes.
See the different levels of light houseplants need in our video guide:
Humidity levels
Air humidity varies in different rooms. A bathroom or kitchen will often have high humidity, whereas a living room, especially with the central heating on, will tend to have low humidity.
Many popular tropical plants, such as orchids, need humid air, to mimic their natural growing conditions, so will suffer in a drier atmosphere – their foliage may turn brown and they may fail to thrive. Few houseplants, apart from cacti and succulents, like very dry situations.
There are various easy ways to raise the air humidity around your houseplants – see our video guide for tips:
Temperature
Room temperature can vary from season to season, and between day and night. Locations that become very hot from the direct summer sun or from a nearby radiator can lead to leaf damage. Plants left in sun rooms or conservatories over winter can suffer if night temperatures are too cold. Draughts can be damaging too, and hallways tend to be a particular problem area.
So it’s a good idea to check the temperature over 24 hours in different rooms, so you know how much it fluctuates. Consider moving your plants around during the year to make the most of available light and warmth.
For more on growing houseplants successfully, see our guides: