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Unit 2 · Lesson 6

Signs of too little light

2 min read

A plant short of light rarely dies quickly. It slowly runs down, which is why the signs are easy to miss.

Watch for small new leaves, slow or no new growth, yellowing leaves, and stems that stretch with long gaps between leaves, giving a leggy look. In severe cases new growth is pale as well as stretched, because the plant is not making enough chlorophyll. This pattern of long, weak, pale growth is called etiolation.

Plants also bend towards the brightest side. The hormone auxin collects on the shaded side of a stem and makes those cells grow longer, so the stem curves towards the light. This is phototropism, and a strong lean tells you most of the light is coming from one direction.

The fix is more light: move the plant closer to a window or add a grow light, stepping it up gradually if it will now get direct sun.

Key points

  • Small leaves, slow growth and long gaps between leaves point to low light.
  • Long, weak, pale growth is called etiolation.
  • Leaning towards the window shows the light is one-sided.

Try this

Compare the newest leaves on one plant with older leaves lower down. Are they smaller, paler or further apart?

Check yourself

A plant has long, thin stems with big gaps between small, pale leaves. What is the most likely cause?

Read more in the reference

Sources

  1. Troubleshooting Common Problems: Houseplant How-To — SDSU Extension
  2. Etiolation — Wikipedia
  3. Phototropism — Wikipedia
  4. Moving indoor plants outside for summer — Iowa State University Extension
  5. Lighting for houseplants — University of Illinois Extension

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