Adiantum thongthamii

Adiantum thongthamii is a rare maidenhair fern endemic to Thailand, known only from a very restricted locality (sandstone rock crevices on ridges of Koh Chang, Trat Province), typically growing at elevations of around 500–650 m.

Features:

• Short-creeping or erect to suberect rhizome, covered with shiny reddish-brown linear scales.

• Fronds simply pinnate; leaflets (pinnae) 3-6 (rarely up to 9) pairs, pinnae with lobed margins, densely covered in hairs on both surfaces.

• Sori numerous (5-10 per pinna), margin sori under false indusia that are reddish-brown and hairy.

Care Tips:

• Light: Provide bright indirect light; avoid direct harsh midday sunlight. It naturally occurs partly exposed but in rock crevices, so some filtered sun may be tolerable but shade is safer.

• Substrate / Soil: Use a well-draining, mineral-rich substrate, possibly with sandstone chips or gritty mineral content to mimic rock crevices. Also include organic matter to retain moisture without waterlogging.

• Moisture & Humidity: Keep soil evenly moist, avoid letting it dry out. High humidity is helpful because in its habitat it would receive moisture from ambient humidity and possibly mist/rain.

• Temperature / Elevation Conditions: Moderate temperatures reflecting mid-elevation tropical climate (~500-650 m). Avoid cold (especially sudden cold) and avoid very hot, dry conditions.

• Protection: Because it grows in exposed rock patches, protection from extremes (excess sun, drying wind) will help. Possibly acclimate gradually if moving from nursery/growth house.