Light Basics for Plant Parents

These are the main questions plant parents ask themselves – how much light does this plant need or is it getting enough light?

Different plants have different light needs, but ALL plants need light – its how they make their food through photosynthesis.
Light is so crucial, that the growth rate of the plant is proportional to the intensity, quality, and duration of light it receives.

Low / Indirect / Direct Light

Each plant processes light differently, and with time and observation, you can deduce which plant has what light requirement just by looking at their leaves and stems.
This illustration by Leon & George shows lighting intensities, using on a north facing window.

Plants grow in the light spectrum of 400 to 740 nanometers, with optimal photosynthesis occurring at 430nm.

Low Light
Plants can survive, but not thrive, in low light. ‘Low light’ plants receive no direct light and do well in south facing windows, or 2m from a sunny window.
Bright-Indirect Light
Place your plants about 0.5m from a north facing window, and not in direct light.
Bright / Direct Light
Place your plants in a north or west facing window, to receive a higher amount of direct sunlight.

These are 3 plants that are tolerant of light on the higher end of the low-light spectrum. From left (Aglonema, sansevieria laurentii, Zamioculcas zamiifolia)

These plants do well in bright indirect lighting. From left (Ficus elastic, Calathea lancifolia, anthurium clarinervium, Monstera deliciosa).

Most all cacti and succulents thrive in bright direct light, and have evolved ways in which to protect themselves from the suns harsh rays. From left ( Kalanchoe, Bird of Paradise (not a succulent), Senecio crassissimus)

What to ask yourself before buying a plant.

  1. Does my living space allow enough quality light in?
  2. What kind of plant parents am I – an over or under-waterer? Am I a helicopter plant parent or am I forgetful?
  3. Will the plant fit into the aesthetics of my home? Does my home provide enough space for the plant I want, say a ‘Fiddle Leaf Fig’?

Additional Things to Consider

Windows: Is your glass clear or reflective? Clean or dirty? A clean window will allow 86% of light intensity to pass through and reach your plant.
Mirrors: Mirrors help to reflect light, providing more light to darker, low-lit rooms. This allows you to have plants in your room that may otherwise have had to go in a north facing window.
Light Compensation Point: **This is the point where photosynthesis = food usage via respiration. If this point is reached but not exceeded, the plant is neither growing nor dying, just existing. This will eventually cause the leaves to die off; eventually killing your plant.
Too much light? If this is the case, your plants leaves will either pale or burn. Move your plant further away from the window to avoid irreversible damage.

**Science and the Garden: The Scientific Basis of Horticultural Practice, 3rd Edition edited by David S. Ingram, Daphne Vince-Prue, Peter J. Gregory.