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Fern terrariums: choose the roots, fronds, and care you can manage

Compare true ferns with Frosty fern, spikemoss, and asparagus plants before a small nursery pot becomes a crowded display.

By Terrarium GuideSources & editorial method

The short answer

For a reachable humid planting, compare an identified maidenhair fern when you can keep its roots consistently moist, or the compact fern in the RHS N. duffii / N. cordifolia ‘Duffii’ horticultural entry when its fronds fit. Choose by actual growing room and care: a broad bird’s nest fern, an exposed-rhizome rabbit’s foot fern, and a button fern with lower humidity needs are different decisions.

Keep the container openable, provide the named plant’s light and root moisture, and leave room for inspection and removal. Frosty fern and spikemoss are Selaginella; asparagus fern is a flowering plant. Their fern-like appearance does not establish the same care or suitability for a permanently sealed jar.

Evidence[4][2][5][6][7][10][11][16][17]

Which true fern matches your growing space?

True-fern choices: roots, growing direction, and the reason to change the plan
Plant and identity checkLight and water directionGrowing room and your decision
Delta maidenhair · Adiantum raddianumFiltered light with humidity and consistently moist roots. NC State warns against root drying, full sun, and excessive shade. Its species profile describes creeping rhizomes and 1–2 ft. height and width in ordinary culture. Compare when you can inspect moisture and allow spreading fronds; fine leaflets do not mean a permanently tiny plant.
Lemon button · RHS N. duffii entry, listing N. cordifolia ‘Duffii’Bright filtered light, moist draining compost, moderate to high humidity and ventilation; RHS explicitly describes terrarium use. Choose for an upright frond clump when the 10–50 cm source size band and actual specimen fit. Keep runners and crown reachable; a compact fern still needs more headroom than a groundcover.
Bird’s nest fern · Asplenium nidusBright filtered light or light shade; humid air and moist, porous medium. A broad rosette of undivided fronds needs lateral room and an accessible center. NC State lists ordinary species dimensions of 3–5 ft. high and 2–3 ft. wide: choose a suitable larger display or a verified compact form, not an unnamed juvenile for a narrow bottle.
Rabbit’s foot fern · Davallia fejeensisGood indirect light; moist medium with some surface drying. NC State specifies letting the top ½ in. dry between waterings. Fuzzy rhizomes grow over the surface and pot edge. Keep them above the soil and leave lateral space; a permanently wet buried-rhizome bed is a different environment.
Button fern · Pellaea rotundifolia (NC State: Hemionitis rotundifolia)Indirect indoor light and regular water in a draining mix; NC State says it does not require the humid air of many other ferns. Compare for a reachable draining pot when you do not need a very humid enclosure. It is distinct from lemon button fern; rounded leaflets do not settle the identity or justify saturated roots.

Evidence[4][2][5][6][3][7][17]

Scope and important limits

A useful fit when

  • Choosing a named indoor fern or distinguishing a fern-like retail plant.
  • Comparing rooted pots, exposed rhizomes, growing room, moisture checks, and reachable maintenance.

Use another path when

  • Treating every fern as a miniature tropical plant or every humid plant as a sealed-bottle candidate.
  • Using a parent-species dimension as a fixed cultivar limit, or a small retail pot as an adult measurement.

These comparisons apply source guidance to the actual display decision. They do not create a shared planting assessment or establish long-term sealed performance. Named plant and cultivated-form limits stay with each comparison.

Look at the growing structure before choosing the container

These true ferns need different checks even when both are sold in small pots. Use their visible structure with the comparison above; the photographs do not establish adult size in glass.

Maidenhair · a spreading canopy
A potted maidenhair fern with arching dark stems and many small green leaflets.
Follow the arching dark stems beyond the pot. Small maidenhair leaflets still form a spreading canopy; compare the whole frond span with your opening and growing room. Image: André Karwath · CC BY-SA 2.5
Allow room around the whole frond, not just each small leaflet.
Check
Adiantum raddianum has arching fronds and creeping rhizomes. NC State’s ordinary-culture dimensions are 1–2 ft. high and wide.
Action
Choose only when you can check its consistently moist rootball and leave lateral clearance. Use the frond span and care opening to assess the actual specimen.
Stop or reassess
Fine leaflets do not establish a permanently miniature plant.

Evidence[4]

Rabbit’s foot · a surface rhizome
A mass of exposed brown fern rhizomes beneath finely divided green fronds.
The brown branching structures beneath the fronds are exposed rhizomes. Leave their growing surface clear and room beside the pot; this large specimen does not set a miniature display’s dimensions. Image: David J. Stang · CC BY-SA 4.0
Keep the creeping rhizome exposed and give it a route over the surface.
Check
Davallia fejeensis forms fronds along fuzzy rhizomes. They can extend beyond a pot edge; NC State advises some surface drying between watering.
Action
Choose an accessible draining pot or suitable support when you can maintain that routine. Keep rhizomes above the medium rather than burying them under decorative moss.
Stop or reassess
A continuously wet buried root zone is not the same growing arrangement.

Evidence[6][3]

Check the cultivated form behind lemon button fern

UConn describes its lemon button entry at about 12 inches tall. That named-entry description and larger parent-species reports have different scope; they are not values to average into a bottle-size promise.

Plant records

A compact Nephrolepis cordifolia plant labeled Living Lace Cute as a Button by the photo source.
Nephrolepis cordifolia Living Lace® Cute as a Button™ Image: Cindy Christian · CC BY 4.0

Identity record

Nephrolepis cordifolia

The source labels this photograph Living Lace® Cute as a Button™. Use it to recognize that pictured form, then verify the plant you are buying.

The photograph does not identify Duffii or establish a mature size for every lemon button fern.

Read the plant profile

Make the purchase decision

Request the species and cultivated-form label, current frond span, expected growth, and propagation origin. Test whether the whole rootball and fronds can pass through the opening. Leave a removal route before runners or new fronds crowd adjacent plants.

Evidence[2][1]

Evidence[3]

A fern name can describe a different kind of plant

Fern-like plants: identity, growth, and the care decision
Plant or source-specific groupWhat matters in the displayChoose only with this management
Krauss’s spikemoss · Selaginella kraussianaA low creeping vascular plant, distinct from true moss and true ferns. Humid air and indirect light accompany rapid surface spread. Use moist, draining medium and a reachable trimming edge. Do not let a mat cover a fern crown.
Frosty fern · Selaginella martensiiA different Selaginella. Missouri’s Frosty fern form grows upward as well as outward and needs high humidity. For that form, Missouri gives about 65–70°F, at least 70% RH, and moist draining medium. Keep roots above collected water and verify the actual botanical label.
Asparagus fern · Asparagus setaceusA flowering plant with fine fern-like foliage and twining or scrambling stems. Use suitable bright filtered light, moist draining roots, support, and accessible growth control in a larger display. Do not choose it merely because its starter foliage looks delicate.
NC State’s Asparagus densiflorus Sprengeri GroupThe source describes an arching, spreading plant with substantial root and canopy growth, distinct from climbing A. setaceus. Compare the source-identified group and its actual size. Retail Sprengeri naming overlaps other taxonomic usage; an unverified trade label cannot inherit these facts or a fern routine.

Evidence[9][10][11][12][13]

Give fern-like plants their own care route

Use the identity comparison above before choosing a planting method. Selaginella’s creeping edge and Asparagus setaceus’s climbing canopy call for different space and management; neither becomes a true fern because of a trade name.

Evidence[9][11]

Choose the enclosure after the plant’s requirements

You want ferns in a closed terrarium
Use an openable humid container and an identified plant that fits.
Check
Check moisture at a maidenhair rootball and clearance around fronds separately. A lid retains moisture but cannot establish the right root condition, leaf temperature or room for new growth.
Action
Use an openable humid display where the named fern fits; keep glass out of direct sun and open it when excess moisture needs to escape.
Stop or reassess
Do not infer permanent sealed success from a general houseplant or terrarium-use statement.

Evidence[16][8]

One plant needs a different watering interval
Choose independent roots only when shared air and light also work.
Check
Compare maidenhair’s consistently moist roots with rabbit’s foot surface drying, and check each plant’s humidity needs.
Action
Use removable draining pots if their above-ground conditions overlap. Drain outside the display and empty collected water.
Stop or reassess
A separate pot cannot fix incompatible air, light, temperature, or unreachable growth.

Evidence[4][6][14]

The shop plant is small but its form grows broadly
Choose space and maintenance deliberately.
Check
Measure frond span, rosette width, rhizome direction, rootball, and the opening. Ask which form the expected size describes.
Action
Test the full frond span and rootball through the opening. Choose a larger accessible vessel or a verified compact form if the fern would become trapped.
Stop or reassess
Repeatedly cutting frond tips is not evidence that any fern can stay in a narrow bottle.

Evidence[5][2][16]

Place the plant so you can keep caring for it

  1. Inspect and test the whole plant first

    Check the named plant, underside of fronds, roots, and existing medium. Test a removal route without forcing delicate foliage through the neck. Clear space for new growth and for the tool you will use to remove old leaves.

    Evidence[16][5]

  2. Match the medium and growing level

    Use an aerated mix that retains the moisture the named plant needs. Set a rooted crown at its existing growing level without covering it. Keep Davallia’s furry creeping rhizome above the soil surface; leave it room to extend rather than burying it beneath decorative moss.

    Evidence[14][3]

  3. Water the roots and inspect drainage

    Water the medium carefully, let a removable pot drain, and empty collected water. For the shared terrestrial bed, stop before water pools around roots. Inspect actual moisture before the next watering; misting the glass cannot establish that the roots received water.

    Evidence[14][16]

  4. Maintain access as growth changes

    Remove dead fronds and fallen debris with clean tools. Keep a visible crown, inspection area, and reachable mat edge. Move an outgrown plant to suitable space; divide it only when that named plant and your handling method support division. Do not impose a universal trimming or watering calendar.

    Evidence[14][16][9]

Read changes before adding water or fertilizer

Brown dots or lines appear beneath mature fronds
Check for normal spore structures first.
Check
True ferns form spore clusters called sori, often brown or dark when mature. Their arrangement depends on the fern; bird’s nest fern has lines on the underside.
Action
Compare the pattern with the identified plant and look for separate signs of damage or moving pests. Leave normal sori in place.
Stop or reassess
Do not treat every dark mark as a pest or diagnose a disease from color alone.

Evidence[15][5]

Fronds crisp or leaflets drop
Check moisture, heat, light, and air together.
Check
Inspect the rootball and room conditions before watering. Drying is especially consequential for maidenhair; a wet rootball calls for a different check.
Action
Correct a dry root zone according to the species, move overheated glass out of sun, and remove dead growth. Watch new growth rather than expecting dead fronds to become green.
Stop or reassess
Pause added water when the medium is already wet; inspect drainage and decaying roots instead.

Evidence[3][14][16]

Frosty tips change color
Check the cultivated form and feeding history.
Check
For Missouri’s S. martensii Frosty fern form, white tips can be lost with excess nitrogen. It is not a true-fern spore pattern.
Action
Review recent feeding and the actual moisture and humidity before adding more fertilizer. Keep roots above standing water and avoid watering the foliage unnecessarily.
Stop or reassess
Do not use fading white tips alone as proof of nutrient deficiency.

Evidence[10]

Other fern labels still need a specific decision

Boston fern, brake fern, and staghorn fern add different frond sizes and planting methods. RHS’s indoor examples include Boston and brake ferns that grow beyond a tiny starter, while UConn describes staghorn ferns on removable supports that drain after watering. Compare the named species or cultivated form before adding one to this plan.

Hardy outdoor ferns and unidentified miniature-fern assortments do not inherit tropical indoor culture. Confirm the plant’s temperature and seasonal guidance, its growth direction, and whether the seller’s size refers to a juvenile or a mature form. Choose nursery-propagated plants and keep surplus plants out of natural areas.

Evidence[8][3][16]

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Sources and review

  1. WFO Plant List — pinned 2026-06 classification · World Flora Online
  2. Nephrolepis cordifolia — species and cultivated forms · NC State Extension
  3. Ferns: Indoor Growing · University of Connecticut Home Garden Education Center
  4. Adiantum raddianum — Delta maidenhair · NC State Extension
  5. Asplenium nidus — bird’s nest fern · NC State Extension
  6. Davallia fejeensis — rabbit’s foot fern · NC State Extension
  7. Button fern — Hemionitis rotundifolia, previously Pellaea rotundifolia · NC State Extension
  8. Tender ferns — houseplants · Royal Horticultural Society
  9. Selaginella kraussiana — spikemoss · NC State Extension
  10. Frosty Ferns Warm Your Home Interior · University of Missouri
  11. Asparagus setaceus — climbing asparagus · NC State Extension
  12. Asparagus setaceus — growing and support · Royal Horticultural Society
  13. Asparagus densiflorus Sprengeri Group — source-specific group · NC State Extension
  14. Growing Ferns — potting, watering and grooming · University of Georgia Extension
  15. Growing Ferns from Spores — sori and plant development · Iowa State University Extension and Outreach
  16. How to Create and Care for a Terrarium · Iowa State University Extension and Outreach
  17. Nephrolepis duffii — RHS horticultural profile (including the listed Duffii synonyms) · Royal Horticultural Society