Lilliputian landscaping: creating a sustainable terrarium garden

Gardening is a popular pastime that requires an understanding of plants and soil to produce beautiful gardens. In this activity, students will examine the different materials gardeners add to their soil and discuss how these materials are important for plant growth. They will learn how to build a sustainable terrarium by adding a waterbed, mixing their own soil, and transplanting a small plant into their terrarium.

To prepare students to create their terrariums, introduce them to key soil concepts by having them listen to “Sprucing Up Your Springtime Soils” or “Tending to Your Winter Garden.” Tell the students that even if they don’t have a backyard, they can create a small indoor garden by building their own terrarium.

Materials

• Quart-sized clear round plastic food containers (you can use old take-out soup containers) – two for each student
• Pebbles
• Horticultural charcoal
• Potting soil
• Perlite
• Peat moss
• Compost
• Sand
• Nylon stocking, cut to fit diameter of the clear plastic food container – one for each student
• Tape
• Small plants, one for each student. Plants should be small enough to fit into the size of the food container.
• Spoons – one for each student
• Water
• Magnifying lens

Activity one: soil study

• Have students create a chart with two columns labeled “Materials” and “Observations,” respectively. In the Materials column, have students list the following: compost, horticultural charcoal, pebbles, potting soil, peat moss, perlite, sand, and nylon stocking.
• Have students use the magnifying lens to observe the different materials, then record descriptions and/or sketches of each in the Observations column on the chart. Some characteristics to observe and record are size, color, smell, and texture.
• Tell students that these are the materials needed to make a terrarium. Review the definition of a terrarium and have students suggest how to use these materials in a terrarium.
• Have students draw a diagram that illustrates what they think is the best way to layer these materials in their terrarium. Have students compare and contrast their diagrams and explain their choices of layering materials.

Activity two: building biospheres

• Into a clear plastic container, ask students to add three teaspoons of pebbles followed by three teaspoons of horticulture charcoal. Place a piece of nylon stocking over these two layers. Why do the students think that these specific materials were placed at the bottom of the biosphere?
• Have students examine the remaining materials. Should they also be separated into layers to build the rest of the terrarium? Tell students that the remaining materials work best when they are mixed together to create a nutrient rich soil.
• In a separate container, have students mix the following ingredients to make their soil mixture:
  – 4 teaspoons potting soil
  – 2 teaspoons perlite
  – 2 teaspoons peat moss
  – 1 teaspoon sand
  – 2 teaspoons compost
• After the soil mixture is completely mixed, have students gently pour it on top of the pebble/stocking layer. Have students use their thumb to make a depression in the soil mixture large enough for each small plant to fit into, but not so large that the depression is deeper than the stocking.
• Have students add two teaspoons of water to each depression. Why is water being added to the soil mixture before planting?
• Hand out plants to students and have them place each plant in a depression, making sure to cover the roots completely. Add four to five teaspoons of water. Why is it necessary to add more water? Check that the soil appears moist. If the soil appears dry, add one teaspoon at a time until the soil becomes moist.
• Rinse the empty clear plastic food container, and place it over the container with the plant so that the two openings are facing each other. Using tape, seal the two containers together. Why is the container being sealed?
• Review the diagrams that the students created earlier. Were any of the students’ suggestions for layering the terrarium different? Could any of the models that differ still serve well as a terrarium?
• Review with students the best way to maintain their terrarium. What would the plant need to survive? Have students observe their terrarium for the next few days. What are the different natural processes that are occurring within the terrarium? Have students keep a journal recording the terrarium’s appearance (water condensation, plant growth, etc.) over time.

The Earth’s biosphere includes a number of vital non-living, or inorganic, components such as sunlight, air, water, and soil that make it possible for life to survive. A terrarium illustrates how living organisms, such as plants, can survive in a closed environment, provided that these vital non-living components are included.

The bottom of the terrarium consists of a waterbed that filters impurities from the water and soil. It also prevents mold growth by promoting drainage, so that the soil does not become too wet. The horticultural charcoal is added for filtering, and the pebbles allow for water drainage. The nylon stocking prevents the soil mixture from seeping into the waterbed.

Since the terrarium will be sealed, each ingredient in the soil mixture is important for providing the right amount of nutrients. The soil mixture consists of five materials, each with an important role in a terrarium. The compost is made of decomposed plant matter and enriches the soil with necessary nutrients. Perlite can absorb and hold extra nutrients and moisture until they are needed. Perlite also improves soil aeration by keeping the soil mixture loose so that minuscule air pockets can form, which assists in water drainage. Like compost, potting soil also contains nutrients needed for plant growth. Peat moss improves aeration and adds more nutrients. Lastly, sand adds stability and improves the aeration of the soil mixture.

Once the two containers are sealed, the plants will recycle the water as the moisture condenses and returns to the soil. If the right amount of nutrients and water is sealed within, then the terrarium will only need sunlight to ensure the well-being of the plant indefinitely. A terrarium can last for years.

Topics for class discussion

• Why did the soil mixture require different amounts of compost, potting soil, peat moss, perlite, and sand instead of the same amount of everything?
• Will the soil mixture used in this lesson promote growth in other types of plants? Would a cactus survive in this terrarium?
• Why are water droplets forming on the sides of the terrarium?

Vocabulary

• Horticulture: the science of cultivating plants.
• Terrarium: an enclosed container to grow plants.
• Compost: a mixture of decayed plants and other organic matter used for enriching soil.
• Perlite: a grayish or white volcanic mineral used in horticulture for promoting aeration and retaining moisture.
• Biosphere: the part of the Earth and its atmosphere in which living organisms exist.

• Have students make daily observations of terrarium growth in their science notebooks. The data can be graphed and compared to other terrariums.
• Have students research different types of biomes that make up the Earth’s biosphere. What are the living and non-living components that make each of these biomes unique?
• Learn about your official state soil through this online interactive.
• Find out what it takes to become a soil scientist.
• Discover more soil mixes with an excerpt from “Building Soil: A Down to Earth Approach.“

National Standards: NS.5-8.1, NS.5-8.3

This lesson plan was created by the New York Hall of Science in collaboration with Science Friday as part of Teachers Talking Science, an online resource for teachers, homeschoolers, and parents to produce free materials based on very popular SciFri Videos to help in the classroom or around the kitchen table.

The New York Hall of Science is a science museum located in the New York City borough of Queens. NYSCI is New York City’s only hands-on science and technology center, with more than 400 hands-on exhibits explore biology, chemistry, and physics.