STEM Mystery:

Burning Bush

Grades 3-5

Why does one bush grow faster than another?

The Mystery:

Gabby loved plants! She knew that someday she would have a job that would let her work with plants all day. Because Gabby was so interested in growing flowers and bushes, her family let her take care of their garden. Her family and friends called her Gabby Gardener. What she liked most of all was looking for problems in her garden that she could solve.

This year Gabby noticed a new problem. She had two striking burning bushes in her front yard, but one bush was growing faster and larger than the other. She decided to practice her science thinking to solve this mystery.

Career Description and Education:

There are many jobs for people who want to work with plants. Anyone with some land and a few tools can grow plants for food or for their beauty. You can grow trees, bushes, flowers, or vegetables. People with a lot of farmland and larger tools can grow large amounts of food like fruit trees, vegetables, or grains like wheat or corn.

If you like plants and science, you will probably want to go to college to study botany, biology, or ecology. If you want to work in a plant business, you can become a horticulturist, a landscaper, or an organic farmer. If you are more interested in the environment, you can become a biologist or conservation scientist, a forester, or a soil scientist.

Solving the Mystery:

Like a good scientist, Gabby started by brainstorming some ideas about what plants need to grow. Help Gabby think through each idea to decide what might be making one of her bushes grow bigger than the other. Use your worksheet to help you.   



Gabby knew that plants need air to grow. This is a map of Gabby’s road, the sidewalk, her house and driveway, and the bushes. She decided to take a look at how well air circulated around the two bushes. What do you think? Is lack of air circulation likely to be a reason for one bush to grow a lot more than the other? She aso looked at pollution that might be coming from cars. Is one bush likely to be impacted more from pollution coming from the road or the driveways?


Gabby knew that there are different kinds of soil: clay, silt, sand, or loam. She remembered that loam might be darker because it has lots of dead organic material – or humus – in it. Gabby dug a small hole next to each bush. She put the dirt from each hole in a separate bowl and made a chart of her observations. Do you think there is a significant difference in the soil of the two bushes?

Smaller BushLarger Bush
Colordark browndark brown
Soil Testloamloam
Pieces of Organic Matter
(anything that used to be left alive
Number of worms43


Were the two bushes getting different amounts of sunlight each day? Gabby checked her map again and also made observations during the day. Do you think the two bushes were getting different amounts of sunlight? The yellow arrow points directly east. Gabby’s house faces east, and so gets the most sun in the morning. The house starts to shade both bushes in the late afternoon and evening because the sun moves to the point that it is behind the house as it sets in the west. Do you see anything that might shade one bush or the other?


Gabby watered her garden anytime there had not been rain for five days. She checked the weather for the last week. She saw that it had been hot and sunny for six days in a row, so she went to the tap to turn on her hose and water the garden. She noticed that there was a leak at the faucet and decided that at some point, she needed to fix that. But then she went on and watered each bush the same amount, timing the amount of water she put on each bush so that each bush would receive roughly the same amount of water from her. The blue arrow indicates where the tap, or faucet for the garden hose is.

Room to Grow

Next, Gabby wondered if each bush had enough room for the roots to grow. Most plants can grow with their root absolutely packed in, but at some point, their growth is limited by the space their roots have. The neighbor’s driveway runs along the south side of Gabby’s house. The neighbor also has a large fir tree growing in their yard, right next to their driveway. Gabby can see the roots growing on her side of the neighbor’s driveway.  Do you think space for roots would make a big difference in the size of the bushes?

A healthy, but root bound Snapdragon in a seed pot.

Given all the information Gabby gathered and looked at, why do you think one bush is larger than the other?


  • Idea: Gail Wheatley
  • Writing: Jeanette Kuder
  • Editing: Tonya Schield
  • Illustration: Sandy Loi