The Blue Oil Fern (Microsorum thailandicum), sometimes called the Blue Fern, is prized for its metallic blue-iridescent leaves. It can be a little finicky but thrives with the right conditions.

Light

• Bright, indirect light is best.

• Avoid direct sunlight, which can scorch the leaves and diminish the blue coloration.

• A north- or east-facing window works well.

Water

• Keep the soil consistently moist but not soggy.

• Water when the top inch of the growing medium feels slightly dry.

• Never allow the plant to sit in standing water.

• Use filtered, distilled, or rainwater if possible, as ferns can be sensitive to minerals.

Humidity

• High humidity is essential, ideally 60-80%.

• Great locations include bathrooms with natural light.

• Consider a humidifier or pebble tray if your home is dry.

Temperature

• Prefers temperatures between 65-80°F (18-27°C).

• Protect from drafts, air-conditioning vents, and sudden temperature changes.

Soil

• Use a loose, well-draining mix rich in organic matter.

• A mix of orchid bark, coco coir or peat moss, and perlite works well.

• The rhizome should sit on top of the soil rather than being buried deeply.

Fertilizer

• Feed lightly during spring and summer with a balanced liquid fertilizer diluted to half strength every 4-6 weeks.

• Avoid over-fertilizing, which can damage the roots.

Common Problems

• Brown leaf edges: Low humidity or inconsistent watering.

• Yellowing leaves: Overwatering or poor drainage.

• Faded blue color: Insufficient light.

• Crispy leaves: Too much direct sun or dry air.