Plants for the jar: moss, ferns and creepers
Published Sep 1, 2026 · 7 min read
A closed jar is a rainforest floor the size of a loaf — fill it with rainforest-floor plants and nothing else.
A closed jar is a rainforest floor the size of a loaf. Plants that come from rainforest floors — mosses, small ferns, creeping things with thin leaves — are radiantly happy in it. Plants that come from anywhere dry, sunny or airy will rot within weeks, no matter how pretty the shop label was. This note sorts the candidates by climate, so the plants in your jar want the same weather.
Moss: the foundation planting
Moss is the point of most closed jars. It carpets the soil, holds moisture, hides the edges of everything, and does it slowly and forever. Two kinds to know by shape rather than name: cushion moss — tight, domed pillows that look like tiny green hills — and sheet or carpet moss — flat, spreading mats that drape over stone. Sources, in order of preference: a shop selling live terrarium moss (not the dyed, preserved kind, which is dead); a friend's damp garden wall with permission; or your own shady paving. Lifted moss comes with a thin sheet of grit underneath — keep it, press it onto damp substrate, and mist. It takes a fortnight to decide it lives here and then never asks for anything again.
Ferns: the vertical interest
Small ferns give a jar height and lace. The reliable ones are the miniatures sold as "terrarium" or "mini" ferns: button fern, lemon button fern, small maidenhairs, the dwarf forms of bird's nest and rabbit's foot ferns. Buy the smallest pot available — a fern in a jar will double in a season — and check the fronds are firm and the crown isn't mushy. One fern per big jar, placed toward the back, is plenty; two is a thicket by spring.
The creepers and the small fry. Nerve plant (the one with veined pink or white leaves) is the classic jar plant: it wilts theatrically when dry and recovers in an hour under a lid. Creeping fig runs along the glass and hides the soil line. Baby's tears foams over stones. Peperomias with small leaves, miniature pileas and tiny selaginellas (spike mosses, which love a lid more than almost anything) fill the middle ground. Choose two or three, in different leaf shapes, and let the moss do the rest.
The plants that will rot under a lid
Succulents and cacti, obviously, but also: air plants, most herbs, any plant with silver or fuzzy leaves (the fuzz traps water and moulds), most flowering plants, and — a frequent casualty — the little "dish garden" mixes that shops sell with a cactus and a fern in the same pot, which are doomed in any climate. If the label says "bright light, water when dry", it's an open-bowl plant. If a plant sits in a damp jar and its leaves go translucent and soft at the base within a week, take it out; it wasn't a lid plant and it won't adjust.
Buying and preparing
Buy small, buy few, and quarantine: new plants wait a week on the windowsill in their own pots, so anything hitchhiking on them (fungus gnats, mealybugs, a slug) shows up before it's sealed inside your jar forever. Before planting, knock off most of the shop compost — it's rich and wet and feeds mould — rinse the roots, and trim any yellow or damaged leaves, because inside a lid a dying leaf becomes a mould colony in days. Moss gets a rinse and a squeeze; ferns get the crown checked; creepers get pinched back by a third so they branch rather than trail.
Composing the cast
A jar reads best with one tall thing (fern) at the back, one spreading thing (creeper or nerve plant) in the middle, one stone or piece of wood for the eye to rest on, and moss over everything else. Odd numbers, different leaf sizes, and gaps: a jar planted to look full on day one is a jungle by month two, and you'll be cutting your way in. Half density is the rule.
Questions from the plant shop
Can I use moss from the garden or the park?
From your own garden, yes, and it's the best moss for your local light. From parks and public land, check the rules — many places prohibit lifting anything, and it's polite to take a small patch from a large expanse and never from a single clump. Wild moss carries more passengers than shop moss, so quarantine it for the full week.
Is the moss in craft shops usable?
Almost never — it's preserved moss, dyed and dead, sold for decorating. It doesn't grow, holds no water cycle, and moulds in a sealed jar. Live moss is sold damp, in a tub or bag, and usually says "live" on it.
What about the "safe for pets" question?
Some common jar plants aren't suitable in homes where a cat or dog might get at them; the jar's lid is a partial guard but jars get knocked over. Check each plant on a reputable list before buying if you have animals, and prefer moss and ferns, which are the least troublesome group — but verify for your own household; that part is yours.
Cast assembled and quarantined — now the fiddly hour: planting with chopsticks.