Spring is upon us, and it’s the perfect time to get outside and get some sunlight. It’s also the perfect time to try out crafts that get your hands in the dirt. But spring won’t stick around forever, and for those of us who don’t look forward to the return of gray and chilly days, it’s also the perfect time to brighten up our living spaces with some green, so that we’ve got some insurance against fall and winter. And don’t fear if you don’t have access to nice plant pots, or direct sunlight, or if you’re just tight on space for houseplants. I’m talking about making moss terrariums.

A BRIEF HISTORY OF TERRARIUMS

The word terrarium comes from the Latin word “terra”, for land, and is structured off of the word for aquarium. From their invention, terrariums were designed to handle circumstances under which plants couldn’t normally thrive. The Wardian case, commonly agreed to be the earliest example of a terrarium, was created in 19th-century London by Dr. Nathaniel Ward, who’d been struggling to keep his ferns alive amid the smog and pollution of the industrial city. From there, Wardian cases became widely used both as decoration in middle-class homes and as transport for plants across long seafaring journeys.

What accounts for the success of the Wardian case? The Wardian case, like modern terrariums, was a closed or mostly closed glass container. The glass walls kept the pollution out and kept water in, allowing plants to thrive even in a polluted city and allowing sailors to conserve freshwater while taking plants across oceans. The Wardian case had a huge impact — it broke monopolies on crops like rubber and tea, and allowed for the widespread cultivation of cinchona (the source of antimalarial quinine), so historians credit it with increasing the pace of European imperial colonization. That’s the global history of today’s humble ornamental terrarium.

UNRAVELLING THE MYSTERIES OF MOSS

Before delving into the how-to’s of moss terrariums, it’s helpful to know a little about moss biology and what makes it such a good candidate for a beginner’s terrarium. Mosses belong to a part of the plant kingdom called the Bryophata. And they share a lot of obvious features with other plants — they’re green, they’ve got structures that look like roots, and they need water and sunlight to grow.

That being said, there’s also some things that make moss special. They’re not vascular plants — this means that they don’t have veins on the inside to carry water and nutrients. So although mosses come in a wide variety of shapes and sizes, they’re all quite small, and moss doesn’t have real roots. Instead, those root-like structures are rhizoids. Moss uses rhizoids to cling to rocks and dirt, and not much else. For all those limitations, moss is incredibly diverse and resilient. It’s found almost from pole to pole; anywhere there’s shade and some amount of water, there’s likely to be moss — on trees, on roof tiles, between cracks in the sidewalk, on rocks, on the ground. Some types of moss can grow submerged entirely underwater, and some moss can dry out entirely, then revive when there’s a rainfall. 

Mosses also have a really weird life history. They don’t have flowers or pollen, and moss sperm needs water in order to reach moss eggs and reproduce. Moss is also unusual in that it gets help with reproduction from springtail! These microarthropods forage on dead matter, fungi, and bacteria; they often live on moss and help move sperm from plant to plant. Once moss has been ‘pollinated’, it grows stalks (often reddish or orange) with capsules that contain spores.

If you’re interested in trying to identify moss that you see on your walks, it’s good to have a guide and a magnifying glass handy, but some moss can’t be identified to the species level without a microscope. For terrarium-building purposes, moss can broadly be grouped into “sheet moss” (moss that grows in even, shaggy carpets) and “mood moss” (moss that grows in thick clumps). A few hardy urban species that you might see on the streets or in parks around Philadelphia and the wider Northeast include silvery thread moss (Bryum argenteum), redshank moss (Ceratodon purpureus), and wall screw-moss (Tortula muralis).

HOW-TO: MAKE YOUR OWN MOSS TERRARIUM

This is meant as a beginner’s guide to a simple moss terrarium (compiled from a few different sources), but don’t feel limited by it — with sufficient patience and materials, terrariums can be as simple or elaborate as you want. You can also find a video here!

1. Find an appropriate container.

• Almost anything that’s made of clear glass or plastic will do — a jam jar, a bottle, a decorative box.

2. Find your moss.

• Make sure you have permission to collect it — don’t gather it from public lands or parks without a permit!
• Collect responsibly — don’t take more than you need, choose small fragments of larger patches when possible, and don’t collect fragments that has a lot of sporophytes (since these will help reseed the patch)
• Make sure that what you’re gathering is really moss and not lichens or algae!
• Pay attention to the conditions you’re gathering from. Does this moss like sunlight and dry conditions? Or is it somewhere cold and damp? You’ll want to recreate these conditions to the best of your abilities.
• Moss is quite resilient; you should be able to gather it just by gently pulling it up from where it’s growing, or by scooping some of the soil up with it.

3. Add 1.5 – 2 inches of drainage.

• Gravel or sphagnum moss will both work for this.

4. Put a mesh over the gravel.

• Metal mesh works best, but plastic mesh is good to, or even a plastic sheet with many holes poked through it
• The goal is so that water drains but the next layer of substrate will stay put.

5. Add about an inch of the next layer of substrate.

• Potting soil or just earth from outside will both work.

6. Place your moss.

• If you’re using a narrow-necked container like a bottle, you might want to use tweezers for this step.

7. Get creative with decorative elements.

• Moss can be glued with small dabs of superglue, or tied with thread, to sticks or rocks that you then position in the terrarium
• You can also add pretty rocks, tiny figurines, seashells, or anything else that you like.

8. Once everything else is set, add your springtails.

•  If you have a culture of springtails in a cup, you can pour a little bit of water in it and skim them off the water with a spoon
• Having springtails in your container is important for the long-term health of your moss, since they’ll help it reproduce and also keep mold from forming!

9. Give the terrarium a little misting, and cap it — you’re done!

Maintaining a closed terrarium shouldn’t be too much work. You want to make sure that it’s sitting somewhere where it gets indirect light, and mist it every so often — once every week or two weeks, or whenever the moss seems dry. It’s especially important to make sure it stays well-watered for the first few weeks after you make the terrarium. If your moss goes brown, it could be dried out from underwatering or rotting from overwatering; the best way to distinguish between the two is to feel whether it’s damp.

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