Delta maidenhair fern

Delta maidenhair fern: how do you recognise it?

Habit

Dense, arching clump 30–40 cm tall and 40–50 cm wide, growing from a short, creeping rhizome.

Leaves

Triangular fronds, two to three times divided, with small fan- to wedge-shaped leaflets; fresh light green.

Stalks

Wiry, stiff and glossy blackish brown.

Spores

Brown clusters of spore cases under the folded-over edges of the leaflets; ferns do not flower.

Roots

Fine and shallow; they tolerate neither drying out nor waterlogging.

Plants: March–April · Pruning: March

Why grow it?

• One of the loveliest ferns for indoors, with fine, airy foliage on black stalks.
• It grows well in a bright spot without sun, for example by a north-facing window.
• Perfect for a bathroom or kitchen, where the air is more humid.
• Evergreen: fresh green all year round.
• Suitable for a terrarium or bottle garden, together with other moisture-loving plants.

Delta maidenhair fern: where does it grow best?

• Bright but out of direct sun: by a north- or east-facing window, or a few metres from a sunny one.
• Humid air: in a bathroom, a kitchen or on a tray of pebbles and water.
• Warm and steady, 18–24 °C, and never below 12 °C; away from draughts and radiators.
• Light, humus-rich potting compost, acid to neutral, that holds moisture but drains well.

Light

Bright, out of direct sun

Potting soil

Multi-purpose compost or airy, humus-rich compost

Acidity

Acid or neutral

Watering

Generously

Size

0.4 m tall, 0.5 m wide

Temperature

Minimum 12 °C

Goes well with

• Nerve plant: Likes the same humid air and light shade; lovely together in a terrarium.
• Calathea: Large, patterned leaves next to the fine maidenhair, with the same care.
• Bird’s nest fern: Broad, glossy fronds for contrast, also happy in a bathroom.
• Spikemoss: A low, moss-like ground cover for a bottle garden or terrarium.

Delta maidenhair fern: when and how to plant it?

Plant in March–April.

1. Repot in March–April, only when the pot is full of roots: it likes to be slightly pot-bound.
2. Choose a pot just a few cm wider, with a drainage hole; a plastic pot keeps the compost moist for longer.
3. Use a light, humus-rich compost for ferns or houseplants, perhaps mixed with a little perlite.
4. Set the plant at the same depth as before and firm the compost gently, without packing it down.
5. Water in with lukewarm, soft water and let the excess drain away.

Care

Water

Keep the compost always lightly moist, never soggy. Ideally use rainwater or soft water at room temperature. Never let the root ball dry out.

Humidity

Stand the pot on a tray of pebbles and water, or group it with other plants. A bathroom with daylight is ideal.

Feeding

From April to September, a half-strength liquid houseplant feed every four weeks.

Brown fronds

Cut withered fronds off at the base; new ones will replace them.

No leaf shine

Do not use leaf-shine products: the delicate foliage cannot cope with them.

Repotting

Every one to two years in spring, or divide it when it gets too big.

Tip: Stand the pot on a tray of wet pebbles: the water evaporates around the plant and keeps the air humid without the roots sitting in water.

Delta maidenhair fern: when to prune it?

Pruning months: March.

When: Remove brown fronds all year round. If the plant looks bare or dried out in March, you can cut everything back.

How:

• Cut withered or yellow fronds off with their stalk, just above the compost.
• If it has dried out completely, cut all fronds back to just above the compost and keep it moist: it often regrows within a few weeks.
• Combine a hard cut in March with repotting or dividing.

Caution: Never cut into the rhizome: that is where the new fronds come from.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In March–April when repotting: cut the clump into two or three pieces with a sharp knife, each with roots and a piece of rhizome, and pot them up separately.

Spores

Lay a ripe frond underside down on paper to catch the spores. Sprinkle them on moist, sterile compost in a covered tray, in a bright, warm place. It takes months before small ferns appear.

Delta maidenhair fern: how does it get through the winter?

• Houseplant: it stays indoors all year and cannot take temperatures below about 12 °C.
• Do not stand it above or next to a radiator: the dry, warm air makes the foliage shrivel.
• Water a little less in winter, but never let the root ball dry out; do not feed from October to March.
• In winter it can move a little closer to the window, as the sun is weak; but watch out for cold draughts and icy panes.

Diseases and pests

• Shrivelled leaflets: Brown, crisp leaflets caused by dry air or a dried-out root ball. Cut them off, water and raise the humidity.
• Yellow fronds and rot: Too wet, or a pot standing in water. Empty the saucer and only water when the surface is just starting to dry.
• Scorched leaves: Pale or brown patches from direct sun. Move it to a bright spot without sun.
• Scale and mealybug: Brown scales or white fluff on the stalks. Remove them carefully with a cotton bud; do not spray products on the delicate foliage.
• Red spider mite: Fine yellow speckling and webbing in warm, dry air. Raise the humidity and rinse the plant gently with lukewarm water.

Through the year

• January: Keep lightly moist, away from the radiator. No feeding.
• February: Raise the humidity. Cut off brown fronds.
• March: Cut back if bare. Repot or divide.
• April: Repot. Feed every four weeks.
• May: Growing. Feed and keep out of direct sun.
• June: Water regularly. Top up the pebble tray.
• July: Protect from strong sun and heat. Feed.
• August: Feed. Watch for spider mite.
• September: Last feed of the year.
• October: Slightly less water. Away from the heating.
• November: Rest: less water, no feeding.
• December: Keep lightly moist. Keep the air humid.

Did you know?

• Adiantum comes from the Greek adiantos, ‘unwetted’: water droplets roll straight off the leaves.
• The spores are hidden beneath the folded-over edges of the leaflets.
• The species is named after the Italian botanist Giuseppe Raddi, who collected plants in Brazil in the early 19th century.