Growing Blue Oil Fern
Blue Oil Fern (Microsorum thailandicum) is a stunning iridescent fern native to Thailand, Vietnam, and China. This fern is known for its absolutely stunning metallic blue leaves. M. thailandicum is both epiphytic and lithophytic in its natural habitat, meaning it grows both on the ground and in the trees. These ferns naturally grow in very shaded jungle understories; the blue leaves are actually a fascinating adaptation used to capture more light.
Blue Oil Fern is very much a tropical plant, growing best in warm, moist conditions but easily adapts to household temperatures and humidity, as long as the soil stays moist. The leaves grow from a rhizome that grows horizontally circling the pot or crawling along terrarium walls.
As far as lighting goes, Oil Ferns seem to grow fastest in bright indirect light but will show off more of their stunning blue color if grown in shade similar to a jungle floor. They prefer higher humidity levels but are surprisingly easy to acclimate to household conditions. I would still recommend keeping them in a pebble tray or around other plants if possible. Even indoors, this fern seems to go through seasonal phases of growth and leaf loss, so don’t fret if you lose a few leaves once in a while.
The growth rate is slow to medium depending on the conditions. In normal household conditions M. thailandicum grows very slowly but the growth rate increases with humidity and water access. The fastest growth will be in greenhouse or terrarium conditions. Blue Oil Ferns grow fastest in medium indirect light but you’ll get the most blue iridescent color in full shade.
It’s important to plant in a chunky soil mix that allows for lots of airflow around the roots to prevent rot. Blue Oil Ferns like to be consistently moist (their roots dry out very quickly) so oxygen around the roots is essential to prevent fungal pathogens from taking over.
Propagation is very simple. The leaves sprout from a rhizome that grows just under the soil level. This rhizome can be cut into pieces that will each grow into their own fern. I’ve had success even with small pieces without any leaves on them, although these grow much slower than larger ones with active ferns and roots.