A TERRARIUM IS LIKE a snapshot of nature. Each one a miniature planted world with the power to evoke a pocket rainforest, a slice of desert or even a beach.
Diane Larson is queen of the terrarium universe at Ravenna Gardens, where the botanical creations sell just as fast as she can dream them up. “Glass terrariums reflect light, adding sparkle to everything around them,” she says. Deep winter is terrarium season.
Just about now, I need all the light I can get, so I was grateful when Larson obliged my request for a terrarium tutorial. She begins by gathering the following supplies:
● a clear glass jar
● some gravel
● potting soil
● a bit of decorative sand
● a variety of 2-inch plants with similar growing conditions (how many plants to use will be determined by the size of your glass container).
I know what you’re thinking: How can you plant a container without drainage? Excellent question. Once you add water to your terrarium, you can’t take it out. A layer of gravel in the bottom of your container forms a reservoir to contain any extra water. “But don’t overdo it,” Larson advises. “Most people overwater their plants — you’ll have better luck if you err on the dry side.”
On top of the gravel, Larson adds a layer of sand just around the edge of the jar, which adds a decorative stratum when seen through the side of the container. But this is strictly optional if sand art isn’t your thing. Next, she mounds a couple tablespoons of soil in the middle of the terrarium: regular potting soil for tropical plants, a well-drained cactus mix for succulents and cactuses. Like proper watering, getting the right soil mix is critical to the success of your terrarium. A few well-placed larger stones (or a small branch or shells or crystals) help retain this central core of soil while lending environmental (and emotional) veritas to the composition.
When planting, Larson removes each plant from its container and knocks most of the soil off the roots before using a spoon to settle it into the mound of soil. A chopstick is handy for propping the plant up as you tamp the soil in place. Before topping off the planting with a layer of decorative gravel, Larson cleans the glass walls of the terrarium with a small paintbrush, which also works well for getting soil and sand out of plant crevices. Finally, she waters just enough to settle the plants into the soil. “I use a turkey baster to target water directly to plant roots,” she tells me.
Place your terrarium in a location best suited to the plants’ needs. Cactus and succulents require more light, but avoid direct sun. Glass concentrates heat — you don’t want to cook your plantings.
A well-cared-for terrarium can last for years. A small pocket of soil and no fertilizer help to limit growth. Larson tells people to not be afraid to trim their plants if they’re outgrowing their place in the terrarium. Most nurseries, including Ravenna Gardens, carry DIY terrarium supplies, like glass containers, gravel and decorative sand, along with a variety of small 2-inch plants. Pro tip: Slow-growing, low-water cactus and succulents do really well in terrariums. Then use your imagination to populate your imaginary landscape.