Growing in the Dark: Plants and Light

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Updated on Dec 14, 2012

Plants and light seem to be good buddies, but how far does the friendship really go? While a lot of plants grow happily underneath warm, sunny skies, the light of the sun might not be necessary for growth and health. Do you think you could grow a plant in darkness? Try out this simple and fun experiment to find out how important -- or unimportant -- light is to a plant.


Do plants need light to grow?


  • Six bean seeds
  • Six pots
  • Plant sprayer
  • Potting soil
  • Shelf
  • Cupboard
  • Ruler
  • Notebook
  • Pencil
  • Grow light (optional)


  1. Fill each pot with soil.
  2. Plant one bean seed in each pot. Make sure you gently cover each seed with a shallow layer of soil.
  3. Place three of the pots outside in a spot that receives lots of sunshine. If the weather is too stormy or overcast, position the pots under a grow light.
  4. Place the remaining three pots in a dark cupboard.
  5. Think about what you know of plants and light. Why do you think plants might need light? Why do you think they might be able to do without it?
  6. Remember the question of this experiment: Do plants need light to grow? Write down your guess, often called a hypothesis, in your notebook.
  7. Spray all your planted seeds gently with the mister.
  8. Now it's time to wait. To get the best results, you'll want to observe your seeds for at least three weeks. Make sure you use the mister every couple of days.
  9. At the end of each week, take a close look at each of your pots. Write down what you see in your notebook.
  10. Once a full three weeks have passed, read through your notes. Did the absence of light make a difference?


The seeds in the cupboard, away from the light, will not grow. Only the plants that received light will sprout.


Plants need light -- they can't survive without it. Light is a very important part of photosynthesis, the process plants use to convert carbon dioxide and water into food. Without light, photosynthesis can't work properly, and without photosynthesis, plants don't get all the food they need to grow healthy and strong. A good tip to remember? Plants always need the presence of three things to grow: water, heat and light.

That's not to say, however, that all plants need the exact same levels or types of light. Some plants require lots of warm sunshine, but others are okay with just a few hours of cool light. Do you think you can find out which plants love the heat and which ones are okay without it? Try another growing experiment and play with new ways to study plants and light. Continuing to guess and test your ideas is a big part of being a real scientist!

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