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Thinking Thursday: Greenhouse Experiment

Have you ever visited a greenhouse before?  I love walking through the doors of a greenhouse and feeling the warm, humid air.  We know that greenhouses let us start growing plants sooner – but have you ever wondered exactly how much impact a greenhouse has on the growing process?  In this Thinking Thursday, we are going to set up an experiment so you can monitor just how much the extra warmth and moisture helps a plant to grow.

Find a helpful video on how to set up your greenhouse experiment below:

Greenhouse Experiments


  • Three Plastic Cups (at least one of them must be clear)
  • Scissors or Craft Knife
  • Soil
  • Seeds
  • Water
  • Tape


  1. Gather all your supplies in an area where it won’t hurt if it gets a little dirty.
  2. With the help of an adult, use the scissors or craft knife to make holes in the bottom of each cup.  This will be important for extra water to go out and air to come in.
  3. Fill two of your cups 2/3 to 3/4 full of soil.  You will use these two cups as pots for growing your seeds.
  4. Place the same number of seeds in each pot, then sprinkle a layer of soil over the seeds that is around 1/4 of an inch thick.
  5. Gently water or mist your soil so the top layer is soaked through.  Set one of your pots aside – it is finished!
  6. For your other pot, place your third cup upside down on top of the pot so the lips of the cups are touching.  Use tape to secure.  This pot will act as your greenhouse.
  7. Place your pots together in a window so they get plenty of sunlight and add water as necessary to keep the soil moist.
  8. As you watch your plants grow, monitor their growth.  Look to answer questions like:
    1. Did the seeds in the greenhouse sprout on the same day as the seeds in your uncovered pot?
    2. Do the same number of seeds sprout in both pots?
    3. Do you have to water your uncovered pot more or less often to keep the soil as moist as your greenhouse?
    4. Are your plants growing faster in one of the pots?
  9. Once your plants have outgrown your pots, you can transplant them to bigger pots or to a garden.


Thinking Thursday projects will be posted each Thursday (except for holidays) throughout the museum closure for COVID-19.  For a full list of previous projects, visit our Thinking Thursday website.

Questions? Contact Sarah, the museum's education coordinator.