The Blue Oil Fern: Care, History, and Why It Looks Like Moonlight on Water
““Fronds iridescent blue in live material; rhizome creeping, densely scaly…””
Some plants bloom in color. Others shimmer.
The Blue Oil Fern (Microsorum thailandicum) — an iridescent fern that glows as if lit from within, catching light like a dragonfly’s wing. Native to the limestone forests of northern Thailand, this is one of the most captivating and strange members of the fern world — and it just might be your next botanical obsession.
The first time I saw one was at the New Orleans Botanical Garden when I was swept away by its blue, glossy shimmer and succulent-like leaves, which began a years-long obsession to find one.
Advice that we often share about plant care is to first learn about its habitat and then attempt to replicate its conditions. So let’s do a thorough and delightful (hopefully) examination into its care, history, and why it deserves a special spot in your collection ( it absolutely does).
🔮 What Makes the Blue Oil Fern So Unique?
✨ Iridescent Leaves – Its striking blue sheen isn’t from pigment. It’s a trick of the light caused by structural coloration, where microscopic surface layers reflect blue wavelengths.
🌱 Epiphytic Nature – In the wild, it grows on rocks or trees, not in soil.
🧪 Scientifically Fascinating – Researchers have studied it for its unusual light-reflecting properties — it’s one of very few plants known to shimmer this way.
🌿 Rare in Cultivation – Only recently introduced to specialty horticulture, and still considered hard to find.
A Brief History of the Blue Oil Fern
Discovered & Described: First scientifically recorded in 2001 by botanists Hennipman & Nooteboom in the rainforests of Thailand.
Native Habitat: Cool, shaded, and damp forests with high humidity and filtered light, often growing on mossy limestone rocks or tree trunks.
First Cultivation: Introduced to terrarium culture and rare plant markets around 2015–2020 via tissue culture propagation.
Current Status: Still rare, but now available in limited numbers through select nurseries. Sought after by collectors, terrarium artists, and lovers of the weird and beautiful.
What is its Native Habitat Like
A favorite creative exercise for me is to imagine the habitats of these plants. With eyes closed, slow deep breaths with a few sentences that describe these environments, I’m there so let’s go:
We’re at a cool, lush, wet forest in Thailand; its upper story is crowded with branches reaching up toward the rain and sun but down here, it is wet. And dark. The environment vibrates with energy from the water trickling through the limestone and there in the gloom, clumps grouped together of shimmering blue leaves and this is where we find the Blue Oil Fern. Nearby are rabbits foot ferns, orchids of all kinds that enrich this place with a kind of gorgeous mystery.
This vision, based on what I’ve learned of the forests of this region tells me much about its care and how I’d feature it when considering a terrarium design.
🌿 CARE GUIDE: Keep Your Blue Oil Fern Thriving
☀️ LIGHT
Bright, indirect light is ideal
No direct sun — it will bleach or burn the iridescent leaves
Can tolerate low light, but may lose its shimmer
🌡️ TEMPERATURE
65–85°F (18–29°C) is the comfort zone
Avoid temps below 55°F
Keep away from cold drafts or dry heating vents
🌫️ HUMIDITY
Thrives in high humidity (70–90%)
Ideal for terrariums, bathroom windowsills, or a humidity tray
Mist regularly if grown in open air
Brown edges = air is too dry
💧 WATERING
Keep substrate evenly moist, but not soggy
Let top layer of moss or bark just begin to dry before watering again
Use distilled, rain, or filtered water — it’s sensitive to hard tap water (think orchid)
🪴 SOIL / MOUNTING
Mimic its epiphytic roots by using:
Sphagnum moss
Orchid bark
Perlite or charcoal for airiness
You can also mount it on cork bark with sphagnum moss for a showpiece
🍽️ FEEDING
Light feeder — avoid over-fertilizing
Use diluted orchid or epiphyte fertilizer (1/4 strength) once per month during spring and summer
Don’t feed during winter or dormancy
Extra Tips for a Healthy Shimmer
Wipe the leaves gently to remove dust and keep that blue glow visible
Airflow matters — even in terrariums. Use passive ventilation or open the lid for a few minutes daily or at least 1-3 times a week.
Don’t crowd it. Give the fronds space to breathe and show off.