Invasive Species Council of British Columbia

Don’t Pick Up Hitchhikers: Let’s Play-Clean-Go!

Grade: K to 12

Duration: 1-3 hours

Setting: Outdoor

Subject: Science

Physical Activity: Yes

Students go on an outdoor adventure – in the schoolyard, neighbourhood green spaces, or on a field trip- and investigate how plants and animals can hitch a ride on them and their gear.  By taking part in “PlayCleanGo” – students learn about best practices that protect natural habitats and biodiversity by stopping the spread of invasive species.

Inquiry Questions
  • How do invasive species spread?
  • What invasive species are found in my region?
  • What can I do to prevent the spread of invasive species in special places near me?
BC Curriculum Links

Science Big Ideas

Connected to all K-7 Biology Big Ideas, for example:

  • Plants and animals have observable features (K)
  • Living things have features and behaviours that help them survive in their environment (Grade 1)
  • Living things have life cycles that are adapted to their environment (Grade 2)
  • Living things are diverse, can be grouped, and interact in their ecosystems (Grade 3)
  • All living things sense and respond to their environment (Grade 4).

Science Curricular Competencies      

Numerous Science Curricular Competencies are addressed for all grades, for example:

  • Experience and interpret the local environment (Grades K-10)
  • Express and reflect on personal experiences of place (Grades K-10)
  • Demonstrate curiosity about the natural world (Grades 3-4)
  • Make observations in familiar or unfamiliar contexts (Grades 5-6)
  • Observe, measure, and record data (Grades 5-8)
  • Small collection containers with lids; clean and empty egg cartons, and/or small ziplock bags. (Plan ahead and collect prior to recycling day). 
  • Masking tape and permanent marker or pens for labelling containers
  • Backpacks for students to carry their own containers and other optional gear

Some optional materials that could be useful for this activity:

  • Tarps/old sheets or ground cloths
  • Magnifiers
  • Rulers
  • Large-sized wool socks that could fit over students’ shoes (and that are OK to get dirty)
  • Boot brushes (To order some from ISCBC go to the Online Store and Merchandise tab)
  • Hand sanitizer
  • Gloves (gardening gloves or thin latex)
  • Field guides or identification apps to help identify species found
  • Clipboards and writing utensils if you plan to use the Hitchhiker Tally Sheet
Documents to Download

Invasive species are introduced, non-native species that negatively impact the environment, the economy and society. For a general background on invasive species and their impacts, read Background on Invasive Species for Educators.

Invasive species have certain characteristics that help them to spread and take over, including:

  • They produce numerous seeds or offspring
  • Their seeds or offspring spread easily and effectively
  • They quickly establish and thrive, displacing native species
  • They lack predators or diseases that keep their populations in check

Many invasive plants produce thousands of seeds that are readily dispersed by wind or by sticking to clothing, pets, vehicles, or outdoor gear. When we go outdoors, we may inadvertently pick up “hitchhikers” in one location and then transport it to another place, where the seeds germinate, grow and the invasive species takes over new areas.  Plants and insects can cling to shoes, vehicles, bike or car tires, clothing, even the fur of pets. Even your backpack could pick up a hitchhiker when it brushes against some plants as you walk along a trail.

We can all play our part and prevent spreading harmful hitchhikers to the lands we love by following best practices when in the outdoors, known as PlayCleanGo

PlayCleanGo Steps:

  1. Arrive at a recreation site with clean boots and gear.  Stay on designated roads and trails to minimize impact and keep any invasive species local. 
  2. Before you leave a site, clean your gear:
    • Remove plants, insects and mud from your boots, gear, and pet. Pick off seeds and burrs and brush off dirt. 
    • Clean your footwear at a trailside boot brush station, if available or pack and use your own boot brush.
    • Check your tires on bikes and ATVs. Remove any mud or plant parts before moving to a new area.
  3. With clean gear you are ready to move on to the next location or head back to school or home!
  4. Learn to identify common invasive species and report them. Report unusual or unfamiliar plants and wildlife that you may see.

In addition to PlayCleanGo, some other ways that we can prevent the spread of invasive species when we are recreating outdoors are by practicing Clean Drain Dry and Buy Local Burn Local, described below.

Clean Drain Dry.  Aquatic invasive species, such as Eurasian watermilfoil and Zebra and Quagga mussels, can be spread from one body of water to another via watercraft (boats, canoes, kayaks) and fishing gear. To protect our lakes, streams, and wetlands, people can clean, drain, and dry their boat and gear on land.  

Buy Local Burn Local. Firewood can harbour invasive insect pests such as Gypsy moth and the Emerald Ash Borer. In order to protect our forests from harmful, wood-infesting species and diseases, don’t transport firewood—buy it where you burn it.  


Before the field trip it is helpful to have had some discussions and have done some activities to introduce the issue of invasive species, their impacts, and some ways that we may help prevent their spread.   See the Additional Resources and Related Activities sections below to download, or link to suggested resources and videos.

  • Group discussions or Think/Pair/Share:
    • What types of “outdoor adventures” do you like to take part in?  For example, walking the dog on trails, hiking, camping, fishing, mountain biking, hunting, off-roading, kayaking, sailing. 
    • Have you ever discovered any plants or insects on your clothing, gear, or pets’ fur after being outdoors?
    • Have you ever seen boot brush stations or boat inspection stations? What are these for and why might they be important?
  • Show photos of some species that commonly “hitchhike”, such as Burdock burrs on a dog or livestock, Puncturevine on a bike tire, or Hound’s tongue on clothing or boots. 
  • Brainstorm: What can we do to prevent unwanted species from hitching a ride on us and spreading to a new place?  Introduce PlayCleanGo steps. Tell students that they are going to do a fun and active investigation to learn how to Play, Clean and Go! 

Step 1: Play! 

Choose the type/s of activities that best suit the age and abilities of your students and the location of your school.  Some ideas:

  • You could walk together as a class on a park trail or in an area that has unmown, tall grasses. 
  • If all students have bikes, you could have a class biking field trip in and around your school field or in the neighbourhood. 
  • Students could be assigned homework to “Play” after school or on the weekend with their family or friends by going on a bike ride on a trail, walking their dog in a park, or other outdoor activity. 


  • Have students wear long pants and long socks that can go over their pant cuffs and a long-sleeved shirt.  This will allow sticky seeds or plant parts to cling to socks and clothing and will also prevent insect bites or ticks. 
  • Another fun and effective way to look for “hitchhikers” is to have everyone wear an old pair of big wool socks over top of one or both of their shoes. You can often buy a package of adult wool socks cheaply from thrift stores or dollar stores.

Step 2: Clean! 

After the outdoor activity in Step 1, students need to clean their gear.  This is the critical step to prevent the spread of invasive species and where students inquire and investigate.  You may want to have protective gloves or hand sanitizer. Remember, follow the steps below before you leave Site #1!

Before you leave the location where you Played in Step 1, everyone needs to inspect and clean their clothing and gear.  Go to a paved area or set up tarps/ground cloths or old sheets on the ground for students to sit or stand on while they look for hitchhikers. If you went for a walk as a class, have students work in pairs to help each other look for and remove all the natural material that is clinging to their socks and clothing.

  • Have students use small collecting containers or clean, empty egg cartons to gather and sort the collected materials.  Students should label their containers with their name, date, and location.
  • While standing on the tarp use boot brushes or other tools to scrape clean all parts of shoes. Don’t forget the bottom of shoes where seeds may be hiding in the mud and soil!  Collect any soil/mud scraped off boots into a collection container with a lid, labeled with name, date, and location. 
  • If you went for a bike ride, follow the same procedure to collect soil or plant material clinging to tires or clothing.
  • Make a tally, take photographs or make sketches or detailed descriptions of any living animals that were found on clothing, such as inchworms or other larvae, or adult invertebrates such as beetles or spiders. Use containers and magnifiers for temporary viewing, but don’t transport any living organisms off site.

Step 3: Go! 

Once students have inspected and gathered everything off their shoes, socks, clothing and/or bike tires, have them work with a buddy to double check and make sure they’re free of hitchhikers.  Once everyone is clear, head back to school with all of your hitchhikers secured in the containers.  (Optional:  Repeat the above steps in a new location in order to compare and contrast what was collected in each.)

Step 4: Hitchhiker Analysis

This step could be done back in class or outdoors at school.

  1. Sort and tally what everyone found. (Use the Hitchhiker Tally Sheet Template from the Documents to Download.)  If you went to more than one location, you could compare and contrast what was found in the different sites and why they might be similar or different based on your observations about the locations and their habitats.
  2. Closely observe what was collected with magnifiers and measure them with rulers. Look for structures that help seeds to attach to fabric or fur, or other features that promote dispersal and hitchhiking. Sketch what you see.
  3. See if you can identify any of the hitchhikers by using field guides, identification apps, and ISCBC resources (see Additional Resources section).  You could also try growing any seeds that were found.  If you collected mud/soil off shoes, you could water it and put it in a sunny location in the classroom to see if anything germinates.  Photographs could be submitted to SEEK by iNaturalist, other apps, or to experts for identification. 
  4. Discuss your results. What was most commonly found and what features did it have that helped it to hitchhike?  Why and how do organisms disperse to new locations?  Compare and contrast features that help some native and non-native species to disperse.  How is PlayCleanGo an effective way to prevent the spread of invasive species?

Step 5: Take the Pledge

Take the PlayCleanGo pledge! Provide students with certificates (see Documents to Download) pledging to do their part to prevent the spread of invasive species by practicing PlayCleanGo.

Share with us!

We’d love to have your feedback and see photos of your students’ learning and participation in this activity. Send to for the opportunity to win resources and have your class have a virtual visit with an invasive species expert!

  • Have students spread the word about PlayCleanGo. Make posters, short video clips, or podcasts about their learning to share with family, the school community, and the greater community, including any parks that were visited.
  • Do research on some invasive species that you found or that are common in your region.  How did they get there and how do they spread?
  • Connect with local stewardship groups to take part in invasive species removal or a restoration project.  Adopt a trail near your school to keep free from invasive species.
Additional Resources

Related Activities (Grades 4-7)

Invasive Species Identification and Reporting

Prevent the Spread of Invasive Species

  • PlayCleanGo to prevent the spread of invasive species when you’re playing outdoors.


Books and Activity Guides for Youth