Indoor Plant Basics: Temperature, by Jim Hole

In an ideal world, you would make your houseplants feel at home by adjusting the temperature of their indoor environment to mimic their natural environment. The reality, however, is that, your comfort is likely to come before that of your plants. And even if you were to choose your plant’s comfort over your own, homes have warmer and cooler spots just waiting to present problems.

Because there are so many species of indoor plants, it follows that there is a wide range of ideal growing temperatures. Fortunately, plants are reasonably tolerant of variations from the ideal. As a general rule, keep nighttime temperatures a few degrees cooler than daytime temperatures: 18–27°C during the day and no less than 15°C at night.

The cooler nighttime temperature is important because it allows plants to store energy. When nighttime temperatures are hot, plants have no choice but to burn a portion of the energy that they worked hard to accumulate during the day. Flowering plants are especially appreciative of a cool rest in the evenings because it prolongs flower life and colour intensity.

Here is a list of conditions houseplants generally dislike:

  • Extreme changes in temperature
  • Cold drafts from windows or exterior doors
  • Hot air blasts from fireplaces, heat registers or radiators
  • Close proximity to hot or cold window panes
  • Night temperatures that dip below 14°C
  • Daytime temperatures in the upper 20°C to lower 30°C range