Background and Guide for Experimenting with Invasive Plants

Ecologists interested in why some invasive plants become noxious weeds have various theories:

  1. Insect pests or diseases controlling species in their original areas are absent in the new location.
  2. Most invasive plants grow readily, producing an abundance of seeds in a short span.
  3. Some may have seeds easily dispersed by animals.
  4. Some reproduce both vegetatively and by seed.
  5. Some flower for a long time.
  6. Many have seeds that do not require conditions like heat, cold, or scraping for germination.
  7. Others have large growing ranges and do not need specific soil or climatic requirements.
  8. Some invasive species have less DNA than normal plants, a feature that assists cells to multiply and spread rapidly.

In this lab activity you will create an experiment that leads to understandings of how an invasive plant takes over the habitat of a native species. You will take two types of local seeds or plants, one, an invasive, exotic plant, the other, a native plant.

Imagine you are an ecologist or ecological restoration specialist assigned to determine how to stop the spread of the invasive plant and protect the native one. You will design an experiment that will help you understand how the two plants grow and interact. You might want to test one of the theories described above as a hypothesis that you intend to validate or disprove.

Develop the experiment with the following guide:

  1. Name your invasive plant and your native plant. What do you know about their growth habits?
  2. What question about these plants will you will try to answer?
  3. Write a hypothesis as to a possible solution to your problem.
  4. How would you design an experiment to test this hypothesis? List possible materials.
  5. Describe an experiment that will effectively test your hypothesis. Remember: some seeds do not germinate readily and require special treatment such as a cold period. If working with seeds, you might include different treatments in your experiment.
  6. Describe steps for your experiment. Identify experimental trials and plant materials with labels. Initial and date each label.
  7. Draw a table to record collected data for the experiment and information needed to test your hypothesis.
  8. Gather needed materials and equipment, set up, and start your planned experiment.

    Follow up:

  9. Collect data from your chart several times weekly for 4 to 8 weeks. Once plants start growing, water them regularly to prevent drying out.
  10. Did anything unexpected happen? For example, did some of the seeds fail to germinate? Why do you think this happened?
  11. Interpret your recorded data. In other words, describe your experimental results.
  12. Does your data support or refute your hypothesis?
  13. What factors could have affected the accuracy of your data?
  14. What can you conclude from this experiment? Using your data, what would you recommend to a forest service interested in controlling invasive species and encouraging native species?
  15. What questions arise from your results? What additional information or research would help understand more about the interaction of these native and exotic plants?