Publication No. 10574
The Grass Won’t Grow
Student Laboratory Kit
Materials Included In Kit
Filter paper, 30 sheets
Additional Materials Required
(for each lab group)
This activity is considered non-hazardous. However, all normal laboratory safety guidelines should be followed. Safety goggles should be worn. Always remind students wash hands thoroughly with soap and water after working in the laboratory.
Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. All materials can be disposed of in the trash according to Flinn Suggested Disposal Method #26a.
Correlation to Next Generation Science Standards (NGSS)†
Science & Engineering PracticesPlanning and carrying out investigations
Analyzing and interpreting data
Constructing explanations and designing solutions
Disciplinary Core IdeasMS-LS1.B: Growth and Development of Organisms
HS-LS1.B: Growth and Development of Organisms
Crosscutting ConceptsCause and effect
MS-LS1-5. Construct a scientific explanation based on evidence for how environmental and genetic factors influence the growth of organisms.
Answers to Questions
___X____ Ryan’s Hypothesis Tested
The Petri dish with just seeds and water was used as a control.
The grass seed covered by the pine needles will not grow.
The grass seeds covered by the pine needles will grow.
Almost all of the seeds in the Petri dish with just water germinated. About half of the seeds in the Petri dish with pine needles germinated. The results may vary.
Ryan’s hypothesis may hold some truth, but it does not explain why all of the grass under the pine tree is not growing.
Answers will vary.
The Petri dish with just water was used as a control.
The grass seed in the Petri dish containing the “pine needle juice” will not grow.
The grass seed in the Petri dish containing the “pine needle juice” will grow.
Almost all of the seeds in the Petri dish with just water germinated. Only a couple of the grass seeds in the Petri dish containing “pine needle juice” germinated. The results may vary.
Emily’s hypothesis was correct. Only a couple of the grass seeds germinated in the Petri dish containing the “pine needle juice.”
Answers will vary.
The boiled “pine needle juice solution” will inhibit grass seed germination completely or nearly complete. Pine trees contain polyphenols and monoterpenes, both of which have been connected with the inhibition of growth in some plants. By “boiling” the pine needles in tap water, these chemicals are extracted and enter the tap water solution. The pine needle bed on top of the seed will likely be inhibitory to the grass seed growth, but depending upon its depth, it may or may not completely inhibit seed growth. The amount of water in the dish and the condition and thickness of the pine needles will affect the level of inhibition. Emily’s hypothesis would seem to have a valid foundation based upon typical results from this experiment.
The Grass Won’t Grow
Emily: “Hey, look, there’s no grass growing under that pine tree.”
Who is right? When scientists are faced with questions like Ryan’s and Emily’s, they find answers using the scientific method. The scientific method is a way of solving problems using a systematic approach. A hypothesis is formulated based on a series of observations, and then the hypothesis is tested by means of experiments designed to either support or invalidate the hypothesis. Based on experimental evidence, a theory is proposed to account for initial observations. If the theory lacks the ability to explain further observations, a new hypothesis may be developed and tested, leading to a refined theory. In a sense, scientific knowledge is continually changing and becoming more reliable as we gather more information, perform tests and improve a hypothesis.
• Record and analyze data—Data, such as observations and measurements, are recorded and then analyzed. If the data support the hypothesis, then the conclusion would state that the hypothesis is correct. If the data contradict the hypothesis, then a new hypothesis must be made and tested.
Student should wear safety goggles when working in the laboratory. Follow all laboratory safety precautions. Wash hands thoroughly with soap and water before leaving the laboratory.
Student Worksheet PDF