Why Are My Drynaria Fronds Curling?

Underwatering

Underwatering is the most common cause of drynaria fertile frond curl. Although drynaria is an epiphyte adapted to tree trunks and surfaces that drain quickly and may experience seasonal dryness, the large, deeply lobed fertile fronds have considerable surface area and lose moisture rapidly. When the growing medium dries out completely, the fertile fronds curl inward within a few days, beginning at the lobes and progressing along the frond. The nest fronds remain brown and papery regardless of watering, so these cannot be used as indicators of plant stress. The creeping rhizome that connects the plant's fronds provides some moisture reserve, but this is limited.

What to do

• Water drynaria when the growing medium has partially dried out, checking by feeling 2 to 3 centimetres into the substrate. In bark-based mixes, this may mean watering every 5 to 7 days in warm summer conditions and every 10 to 14 days in winter.
• For drynaria mounted on boards or in hanging baskets, soak the entire mount or basket in a bucket of water for 15 to 20 minutes, then allow to drain completely before rehinging. This ensures the rhizome and roots absorb adequate moisture, which a quick pour of water may not achieve with a mounted plant.
• After rewetting, curled fertile fronds typically begin to unfurl within 24 to 48 hours if the drought was not too prolonged. Fronds that have dried out and browned will not recover; trim them back to allow new fronds to emerge.

Low humidity

Low humidity causes the fertile fronds of drynaria to curl at the lobes and tips even when the rhizome and roots are receiving adequate moisture. Drynaria grows naturally in tropical and subtropical regions with higher ambient humidity than is typical in UK homes, and the combination of winter central heating and the plant's large frond surface area makes it vulnerable to humidity-related stress. The characteristic lobed margins of the fertile fronds are particularly susceptible to drying at their tips in low humidity, producing a distinctive pattern of tip curl and browning.

What to do

• Position drynaria in a warm conservatory, bathroom, or kitchen where ambient humidity is higher than in typical living rooms. Warm conservatories in particular suit drynaria well, providing good light, warmth, and humidity in summer.
• Use a pebble tray with water beneath the container, or mist the fertile fronds lightly in dry conditions. For mounted drynaria, regular misting of both the rhizome and the fronds helps maintain adequate moisture levels.
• A room humidifier is the most effective solution for UK homes where persistent low humidity affects the plant. Group drynaria with other large tropical plants to benefit from collective transpiration.

Overwatering

Overwatering causes the rhizome of drynaria to rot in persistently saturated growing medium. As an epiphyte evolved to grow on surfaces with excellent drainage and aeration, drynaria has no tolerance for waterlogged conditions. An overwatered drynaria shows yellowing fertile fronds that collapse rather than curl, and the rhizome sections become dark and slimy at their bases. Because drynaria's root system is shallow and the rhizome creeps across the surface of the growing medium rather than penetrating deeply, root rot progresses quickly once it begins.

What to do

• Grow drynaria in a very well-draining substrate such as coarse orchid bark mixed with perlite, or on a mounted board with a small amount of sphagnum moss and bark around the rhizome. Never use standard houseplant compost, which retains too much moisture for drynaria's epiphytic roots.
• Ensure excellent drainage from the container. Drynaria grown in pots should have large drainage holes and the pot should drain freely within minutes of watering.
• Do not mist the base of the rhizome or the roots when watering mounted specimens: apply water to the sphagnum and bark around the rhizome and allow it to dry between waterings. Continuously wet rhizomes rot quickly.

Direct sun

Direct sun bleaches the large fertile fronds of drynaria and causes the lobes to curl and develop scorched, papery patches. Drynaria naturally grows on the shaded side of tree trunks and on rock faces in positions that receive dappled or filtered light rather than direct sun, and the fertile fronds are not adapted to the intensity of direct sun exposure, particularly through glass. In warm conservatories in summer, drynaria must be protected from direct afternoon sun.

What to do

• Provide drynaria with bright, indirect light. In a warm conservatory, position it away from the glass and shade it from direct sun using a slatted blind or other sun-filtering material in summer.
• Outdoors in summer, position drynaria in dappled shade beneath a canopy of other plants. The filtered light through leaves is well-suited to its natural habitat conditions.

Cold temperatures

Drynaria is a tropical to subtropical plant that is sensitive to cold. Temperatures below 12 to 13 degrees Celsius cause the fertile fronds to curl and yellow. Frost kills the aerial parts of the plant, though the rhizome may survive light frost and regenerate if protected. In most of the UK, drynaria requires protection from frost and cold, making it a conservatory or warm greenhouse plant except in the mildest coastal regions where it might survive outdoors in an extremely sheltered position.

What to do

• Maintain drynaria above 15 degrees Celsius year-round for best growth, and above 10 to 12 degrees as a minimum to prevent cold damage to the fertile fronds. Warm conservatories are well-suited to drynaria as long as winter temperatures remain above this minimum.
• In summer, drynaria grows vigorously in warm outdoor temperatures and can be placed outside in a sheltered, shaded, warm position. Return it indoors well before autumn temperatures approach 12 degrees Celsius.

Frequently asked questions

Why are my drynaria fronds curling?

Drynaria fronds curl most often from underwatering or low humidity. Drynaria (basket fern or oak-leaf fern) is an epiphytic fern native to tropical and subtropical Asia, Africa, and Australia that grows on tree trunks and rocky surfaces. It has two distinct types of frond: the persistent, rounded nest fronds that anchor to the tree and collect falling debris, and the larger, deeply lobed fertile fronds that extend outward to photosynthesize. The fertile fronds are the ones that curl visibly when the plant is stressed. Because drynaria grows epiphytically on surfaces with good drainage and aeration, it is adapted to periods of dryness but still requires adequate moisture for the fertile fronds to remain uncurled and productive.

What are the two types of fronds on drynaria?

Drynaria produces two distinct types of fronds, which is one of its most striking and unusual features. The first type are the nest fronds (also called humus-collecting fronds or basket fronds): these are short, broadly rounded, brown, papery fronds that clasp the tree trunk or rock face and form a basket shape around the base of the plant, collecting fallen leaves, debris, and organic matter that decomposes to provide nutrients. The second type are the fertile fronds: large, arching, deeply lobed fronds resembling oak leaves (hence the common name oak-leaf fern) that extend outward to photosynthesize and produce spores. When drynaria is stressed, the fertile fronds curl and may turn yellow, while the nest fronds remain brown and papery regardless of plant health.

How do I water drynaria?

Drynaria should be watered when the growing medium has partially dried out, typically when the top 2 to 3 centimetres of the substrate feel dry. As an epiphyte adapted to growing on tree trunks, drynaria requires excellent drainage and should never sit in waterlogged conditions. Water thoroughly, either by pouring water over the growing medium until it drains from the base of the container, or by submerging the container in water for 15 to 20 minutes and then allowing it to drain completely. In winter, reduce watering frequency significantly as growth slows. The rhizome can tolerate some dryness between waterings, but prolonged drought causes the fertile fronds to curl and eventually brown.

Is drynaria the same as platycerium?

Drynaria and platycerium (staghorn fern) are both epiphytic ferns with two types of fronds, and they are sometimes confused because of this shared characteristic. However, they are different genera. Platycerium is native to Africa, Australia, and tropical Asia and is characterised by dramatic, antler-like fertile fronds and flattened, rounded nest fronds pressed against the mounting surface. Drynaria is from tropical and subtropical Asia, Africa, and Australia and has oak-leaf-shaped fertile fronds and a more basket-like arrangement of nest fronds that stand somewhat away from the surface. Their care requirements are similar, both preferring good drainage, warmth, and moderate humidity, but drynaria generally tolerates slightly brighter light conditions than platycerium.