Microsorum thailandicum

Blue Oil Fern, Blue Strap Fern

Moderate careLithophyteNon-toxic15–30 cm

Microsorum thailandicum grows on shaded limestone cliffs in peninsular Thailand, where narrow strap-like fronds emerge from a creeping rhizome pressed against the rock. The leathery fronds carry a metallic-blue iridescence — produced by microscopic structures in the leaf surface that scatter light back as blue, an adaptation thought to help capture the dim wavelengths reaching the forest floor. It does best in low to medium indirect light with humidity above 70%, conditions easiest to maintain inside a closed terrarium or glass cabinet. Direct sun bleaches the fronds and the blue glow fades; sustained dry air browns the leaf tips.

Build a terrarium with this plant
Blue Oil Fern image

Photo by pratyeka·CC BY-NC 4.0

Care

Prefers very high humidity, low light, with 18–24 °C, and reaches 30 cm at maturity.

Light

Shade tolerant(preferred)Indirect light

Humidity

Very high (80%+)(preferred)High (60–80%)

Temperature

10°C25°C40°C
18°C – 24°C

Soil

Orchid mix(preferred)Sphagnum mixWell draining

Moisture

Moist(preferred)

Propagation

Lift a section of rhizome bearing two to three fronds and its own roots, then pin it to the surface of fresh substrate rather than burying it — buried rhizomes tend to rot. Keep humidity high and the surface evenly moist until new growth appears.

Native range

Native to Indo-China.

Appearance

Growth habit

CreepingClumping

Leaf shape

Strap

Leaf texture

LeatheryGlossy

Frequently asked

Can Blue Oil Fern grow in a closed terrarium?

Yes. Blue Oil Fern prefers very high (above 80%) humidity, which is what a closed terrarium provides, and tolerates shade-tolerant conditions.

Does Blue Oil Fern need drainage?

Blue Oil Fern prefers a moist substrate. Drainage is helpful but not critical; consistent moisture matters more.

What humidity does Blue Oil Fern need?

Blue Oil Fern does best in very high (above 80%) humidity.

Is Blue Oil Fern pet-safe?

Blue Oil Fern is considered non-toxic to common household pets.

How tall does Blue Oil Fern grow?

Blue Oil Fern typically reaches 15–30 cm at maturity.

How do you propagate Blue Oil Fern?

Blue Oil Fern can be propagated by rhizome division or spores.

References

  1. 1

    Kew Plants of the World Online — Microsorum thailandicum

    https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:20002929-1
  2. 2

    Wikipedia — Microsorum thailandicum

    https://en.wikipedia.org/wiki/Microsorum_thailandicum
  3. 3
  4. 4

    Soltech — Blue Oil Fern Plant Care Guide

    https://soltech.com/products/blue-oil-fern-care
  5. 5
  6. 6

    NParks Singapore FloraFaunaWeb — Microsorum thailandicum

    https://www.nparks.gov.sg/florafaunaweb/flora/6/4/6433
  7. 7

    Boonkerd & Nooteboom — A new species of Microsorum (Polypodiaceae) from Thailand

    https://www.researchgate.net/publication/290799062_A_new_species_of_Microsorum_Polypodiaceae_from_Thailand