Quick answer: The best ferns for terrariums are compact, humidity-loving species. Lemon Button fern (Nephrolepis cordifolia 'Duffii'), Bird's Nest fern (dwarf forms), Rabbit's Foot fern, Maidenhair (in sealed builds), Japanese Painted fern (cool builds) and creeping mini ferns like Lemmaphyllum and Microsorum 'Mini' all work well. Give them 70–90% humidity, airy soil or a mount, and bright but indirect light.
Why ferns make great vivarium plants
Ferns evolved long before flowering plants and dominate the humid understorey of rainforests worldwide. In a vivarium they:
- add fine, layered texture that contrasts with broad-leaved plants like pothos and bromeliads;
- tolerate the medium-low light near the bottom of a tall enclosure;
- hold humidity around the soil surface, which helps moss, springtails and amphibians;
- come in epiphytic forms you can mount on cork, and terrestrial forms for the ground.
Best terrarium ferns by size and style
| Fern | Size in a vivarium | Grows | Notes |
|---|---|---|---|
| Lemon Button fern | 15–30 cm | Terrestrial | Tough, compact, lemon-scented fronds. Excellent all-rounder |
| Dwarf Bird's Nest (Asplenium nidus 'Crispy Wave' mini types) | 15–30 cm | Terrestrial or epiphytic | Bold, wavy leaves. Can mount in a cork pocket |
| Rabbit's Foot fern (Davallia) | 15–25 cm | Epiphytic | Furry rhizomes creep over cork. Great on backgrounds |
| Maidenhair (Adiantum) | 15–30 cm | Terrestrial | Delicate. Needs constant humidity; ideal in closed terrariums |
| Button fern (Pellaea rotundifolia) | 15–25 cm | Terrestrial | Prefers a bit less water than most ferns |
| Mini Java fern (Microsorum pteropus 'Mini' / 'Trident') | 8–15 cm | Epiphytic | Mount on wood at the waterline of paludariums |
| Lemmaphyllum microphyllum | 2–5 cm | Creeping epiphyte | Tiny round leaves. Carpets cork and stone |
| Selaginella (spikemoss, a fern ally) | 3–15 cm | Ground cover | Lush, moss-like carpet for very humid builds |
Ferns to avoid in small enclosures
- Standard Boston fern: beautiful, but fronds can reach 60–90 cm.
- Staghorn fern: a stunning mount for very large enclosures, but it outgrows most terrariums.
- Tree ferns and large Asplenium: far too big.
- Japanese painted fern and other temperate ferns: they go dormant in winter and dislike constant warmth. Only use them in unheated, room-temperature builds.
Planting ferns in a bioactive build
Terrestrial ferns want moisture at their roots and air around their crowns. An open, organic substrate like Jurassic ABG Terrarium Mix, Canadian-made by Jurassic Reptile Products, gives them both. Over a drained base of clay balls, it stays moist without going sour.
- Rinse off the nursery soil and inspect the base of the fronds for scale insects and mealybugs, which love ferns.
- Plant with the crown (where fronds emerge) at or slightly above the soil line.
- Tuck a layer of leaf litter and some live moss around the base to hold humidity.
- Group ferns near the back and sides, behind lower plants like fittonia and peperomia, to build depth.
Mounting epiphytic ferns
Rabbit's Foot, mini Java fern, Lemmaphyllum and small Bird's Nest ferns can grow directly on hardscape. Wedge the rhizome into a crack in a cork flat or cork background, pad it with a little sphagnum, and tie it with fishing line until it roots. Never bury a Java fern rhizome. It rots. Full technique: how to mount plants on cork and wood.
Light, humidity and water
- Light: medium, indirect. Under 6,500K LEDs, the middle and lower parts of the enclosure are usually perfect. Direct, intense light yellows the fronds.
- Humidity: 70–90% for most species. Maidenhair and Selaginella want the top of that range and do best in sealed or nearly sealed builds.
- Water: keep the soil evenly moist. Ferns generally tolerate wetter soil than succulents or pothos, but still need drainage.
- Temperature: 18–26°C suits most tropical ferns. Avoid placing them under basking lamps.
Why are my fern fronds turning brown?
| Pattern | Likely cause | Fix |
|---|---|---|
| Crispy tips across the whole plant | Low humidity | Reduce screen ventilation; mist more; check winter humidity |
| Brown, mushy base | Crown buried or soil waterlogged | Replant higher; check drainage layer |
| Old outer fronds browning only | Normal ageing | Trim at the base; your isopods will eat them |
| Pale, yellowing fronds | Too much light or heat | Move lower in the enclosure |
| Sticky residue, small bumps on stems | Scale insects | Remove by hand; quarantine new ferns before planting |
Spore patches aren't pests
Rows of brown dots or lines on the underside of fronds are sori, the fern's spore-producing structures. They're completely normal and a sign of a mature, healthy plant. In a humid vivarium you may even see tiny new ferns sprouting from spores on cork or moss.
FAQ
What is the easiest fern for a terrarium?
Lemon Button fern is the most forgiving. It's compact, tough and tolerant of a range of humidity and light levels.
Are ferns safe for reptiles and amphibians?
The common terrarium ferns listed here are widely used with dart frogs, tree frogs, geckos and inverts. Avoid ferns with herbivorous reptiles unless you've confirmed the species is safe. See our reptile-safe plants guide.
Can ferns grow in a closed jar terrarium?
Yes. Maidenhair, Selaginella, mini Bird's Nest and Lemmaphyllum are among the best plants for sealed jars. Read our closed jar terrarium guide.