How Does Your Garden Grow?

This lesson is designed for high school biology students, but could easily be modified for students in any age group. This project is woven throughout an Ecology unit, and the resulting garden is then an appropriate outdoor classroom for Geoscience, Biology, and Physical Science students.

1. Students learn about their local ecosystem. I start with a lesson on Biomes. Students collect local climate data to create a climograph of their region to determine which biome our local environment best matches. This is followed by a discussion of the challenges faced by plants and animals in this ecosystem, and what adaptations may have developed as a result.

2. Students use a dichotomous key to identify local plants. This activity is most interesting when conducted out in the field, but works well as a classroom laboratory activity if it is not possible to take students out to the field. If presented as a classroom lab, I recommend having fresh samples of a variety of local plants, along with photographs of each plant in its native habitat. Students are asked to identify each plant, using the dichotomous key and to identify adaptations that make that plant suited for the local ecosystem. Students follow up by researching specific plants to find soil and light requirements, pollinators, herbivores, etc. Student research is presented to the class via Powerpoint presentations.

3. The soil of the proposed garden space is tested for nutrients and biotic communities (macro and micro). There are three laboratory acivities that I use for this. Students test the soil for nitrogen, phosphorus, and potassium, as well as for porosity and pH. I present these activities as part of our study of abiotic factors in the environment and biogeochemical cycles. The second laboratory is a study of the macroscopic life present in and on the soil. students use dissection scopes to observe and identify soil insects, worms, isopods, and fungi. This lab is part of a study of communities and food webs. The third soil lab looks at the microscopic life present in the soil as part of a study of decomposition and the role of decomposers in communities. Students culture soil fungi and bacteria over a one-to-two week period (one week if an incubator is available, two if not).

4. Now that students have analyzed the garden soil and know what plants grow in their ecosystem, they can design the garden! Landscaping software makes this easier, as students can try out a variety of designs and see what works best and gives the desired results. My own class garden has four sections, each representing a different California ecosystem; the desert, chaparral, redwoods, and Channel Islands.

5. Local environmental groups and garden clubs are good resources for seeds, plants, and for planting advice. The completed garden provides a perfect spot for hands-on studies of species diversity and communities, using quadrats and transects. Food chains, symbiosis, and bird behavior studies are all three steps away from my classroom. Students are able to observe and document seasonal changes in the garden, and have become much more sensitive to the subtle seasons that we have in Southern California. Changes in the garden are documented with digital cameras, preserved specimens, and student drawings and journal entries.

6. As a follow-up, we have started a composting program to produce our own garden compost, and have been maintaining a worm bin in our classroom. We are currently composting all of the green waste from our school cafeteria (from food prep), and are working on training students to sort their food waste, so that we can compost post-consumer food waste as well.