This is a fun class project, which also produces a nice product – worthy of gift giving or keeping around long-term. Students provide a clean glass jar from home. It should be a jar with a wide mouth, such as a peanut butter jar, a canning jar, or a short squat jam jar. (We’ve also used spaghetti sauce or applesauce jars, plastic tubs, and plastic cups.)
This is part of our geology unit. We explain that the earth is made of layers of different kinds of rocks, and this layering activity is a way to experience that. We also share how mountains break up into big boulders, which break up into small rocks, which break into pebbles, then sand.
We set things up assembly line style, where kids go down the line, and put in first sand (this is an optional layer – it’s an inexpensive way to fill a little space at the bottom of the jar), then rocks and pebbles (important for drainage), then horticultural charcoal (to reduce odors and mold), then cactus soil, then the plant. (We used cacti and succulents.) Pack the soil in a little around the plant, and water it to compress it a bit – otherwise, the first time they water it at home, the soil compresses and leaves the plant poking up out of it. It just takes a few minutes per child with an adult helper.
Succulents are really easy to care for (and I say this as someone who DOES NOT garden, or own any other house plants!) Set them on a window sill that gets a fair amount of sun. And about once a week, give them an ounce or two of water. That’s it.
As an FYI, here’s the products / quantities we used to make 20 terrariums, in case you want to re-create the project. Horticultural Sand – 1 quart ~ $6. (If you have clean play sand, that may be a cheaper option.) Decorative garden rocks – 2 pounds of pebbles, 1 quart of larger rocks ~ $9 on Amazon, cheaper craft rocks at Michael’s. (You could “wild gather” your rocks, but you’d want to clean them so the terrarium is a pretty clean system.) Horticultural Charcoal – 1 quart – $10. Cactus Soil – 3 quarts ~ $9. Succulents – $37. Note: I haven’t had to buy succulents in the past two years, because during the year between classes, I propagate a new crop of baby succulents – it’s super easy but it takes a whole year!