Calvin College

CALVIN - Minds in the Making

Strengthening Liberal Arts Education by Embracing Place and Particularity

Case Study

Service-Learning Partnerships with local Elementary Schools: Creating Native Wildflower Gardens

Description of the Project and Relevance to the Course

In the spring term of Biology 112 (Biology for Elementary Education Majors) within the broad topic of ecology, we highlight the problematic influence of non-native species (also known as ‘biological pollution’).   We begin by asking students to brainstorm answers to this question:  What traits allow some non-native species to become invasive to the point that they degrade native biodiversity? 

From the list generated by students, we focus on one of the answers that inevitably arises – that invasive species may have a greater capacity for reproduction than native species.  This, we posit, is a real-life hypothesis that can be tested and at this point we introduce the students to a local problematic invasive, Purple loosestrife (Lythrum salicaria).  We choose to focus on Purple loosestrife because it is excessively abundant in West Michigan and in wetlands on our own campus.  Furthermore, the factors that lead to the unbalanced success of this plant are not well understood by ecologists.  Together with the class we then design an experimental and announce to the students that we are going to carry out this experiment as a class.

The design includes planting six replicates of 100 seeds each of Purple loosestrife, the results of which are compared with six replicates of 100 seeds each from a variety of native species.  We then assign each pair of students in the class one of the species (we do this by pulling species names out of a hat) and distribute to them a small bag of seeds that had been collected during the previous growing season and over-wintered to break dormancy.

Students count out their allotments of seeds and plant them in small trays (12 trays per flat, hence the utility of using six replicates) that are kept in our college greenhouse.  During the ensuing 4 weeks, the number of emerged seedlings in each tray are counted and recorded at the beginning of each class period (three times per week).  A large data set is thus accumulated.  After all germination has ceased we devote one class period to data processing, which requires students to calculate mean and standard deviation values that they use to generate graphs (mean seedling emergence over time).  These graphs are then used to evaluate the original hypothesis.

Several objectives with regard to the relevance of this project for the course are achieved with this project.  Students engage directly in the scientific process, allowing the scientific method to come to life in a real-world context.  They see why it is important for an experiment to be designed with an initial hypothesis, why replicates are used and how data can be processed and organized in such a way that affords direct evaluation of the hypothesis.  Also, when students are counting their seeds, we have them collect five seeds from each species and tape them onto a common sheet behind each species’ name.  This master sheet is then photocopied so students can see the huge difference in seed size (Purple loosestrife produces the smallest seeds – over 2 million each year by a single plant).  This visual displays provides a springboard to discussing the different strategies plants use in attempting to establish their offspring into succeeding generations. 

Germination success varies widely among the species, with Purple loosestrife typically the fastest and most successful (as high as 90% after just one week).  From the graphs students create, they readily generate evidence that supports the initial hypothesis.  This activity also allows students to make predictions, based on their data, for which species are most likely to be the best competitors with Purple loosestrife.  Usually some species show markedly low germination or fail to germinate at all.  This result provides opportunity to discuss the environmental factors that are required for seed germination to occur. 

After counting is finished and graphs have been produced, the scientific inquiry of the project is complete.  However, the experiment leaves us with a host of valuable native seedlings.  We then use these native seedlings to assist a local school in establishing a native plant garden on their school grounds.  This process is initiated with a seemingly innocent class discussion on the types of plants used in home landscaping and why they are used.  Students are led to identify a list of benefits for utilizing native plants in urban settings.  An appreciation for the value of native plants is developed, including the support of native pollinators, less dependency on chemical inputs, improved genetic diversity by increasing opportunity for cross-pollination, and a deeper appreciation for the indigenous biodiversity of our local ecological context. 

We then devote a class period to hosting students from the partner school.  College students and elementary students are paired up in small groups and the college students (future teachers) explain the experiment and their results to the elementary students.  After this ‘lesson’, which includes an emphasis on the value of planting native wildflowers, the mixed groups together transplant native seedlings into larger pots (Purple loosestrife, of course, is not included in this transplanting effort).  During the last week of class we take Calvin students and the transplanted seedlings to the Elementary school where we re-unite the previously formed groups.  Together the groups outplant their seedlings into a site that had been prepared by the Elementary students.


Next: Relevant Theory and Research