Cinnamon fern

Cinnamon fern: how do you recognise it?

Habit

Broad, vase-shaped clump about 1 m tall and 80 cm wide, from a thick, upright rhizome.

Fronds

Once divided into deeply cut segments, fresh green; at the base of each segment there is a tuft of rusty hairs.

Fertile fronds

Separate, upright fronds in the centre, green at first and then cinnamon brown in April–May; they wither in early summer.

Autumn colour

Yellow to orange-brown in October; then the fronds die back.

Roots

A thick, fibrous rhizome with a dense mass of black roots.

Plants: March–May and September–October · Pruning: March and June

Why grow it?

• Striking in spring: woolly croziers followed by cinnamon-brown fertile fronds among the green foliage.
• A stately, regular vase of fronds for the pond edge or a wet, shady corner.
• Fine autumn colour: the fronds turn yellow to orange-brown before dying back.
• One of the few large ferns that really tolerate wet soil.
• Hardly spreads: the clump slowly widens but does not run.
• The dense clump along the bank gives shelter to frogs and other pond creatures.

Cinnamon fern: where does it grow best?

• Partial shade to shade; in wet soil it also tolerates more sun.
• Acid, humus-rich soil: sand, loam or peat. No lime.
• Moist to wet: ideal on a wet pond edge or in a bog border, where the soil is saturated but the crown is not permanently under water.
• A spot sheltered from strong wind keeps the large fronds looking good.
• Plant 80–100 cm apart: the clump needs room to show its vase shape.

Light

Partial shade and shade

Soil type

Sand, loam or peat

Acidity

Acid

Moisture

Wet

Size

1 m tall, 0.8 m wide

Hardiness

Hardy (to -35 °C)

Goes well with

• Rhododendron: An evergreen shrub that also likes acid, humus-rich soil.
• Royal fern: Its native relative, for the same wet, acid soil.
• Marsh marigold: Golden flowers in March–April on the wet bank, beside the woolly croziers.
• Japanese water iris: Large, flat flowers in summer, on moist, acid soil.
• Water forget-me-not: Sky-blue little flowers at the water’s edge, in the same moist partial shade.

Cinnamon fern: when and how to plant it?

Plant in March–May and September–October.

1. Plant from March to May or in September–October, when the soil is not frozen.
2. Dig a hole twice as wide as the pot and work in plenty of leaf mould or acid, rotted conifer needles.
3. Set the plant at the same depth as before: the crown with the croziers belongs at the surface, not below it.
4. Leave 80–100 cm between plants and firm the soil well.
5. Water thoroughly straight away, ideally with rainwater, and then keep the soil moist to wet at all times.
6. Spread a layer of leaf mould around the plant as a mulch, but not over the crown.

Care

Water

The soil must never dry out. In a wet spot watering is not needed; elsewhere water generously with rainwater in dry periods.

Feeding

Not needed: a layer of leaf mould in spring is enough. No chemical fertiliser and no lime, especially near the pond.

Mulching

A layer of leaf mould or fallen oak leaves keeps the soil acid, cool and moist.

Fertile fronds

Remove the withered brown fertile fronds in June if you do not like the look of them; it is not necessary.

Old fronds

Leave the dead fronds standing over winter and cut them off in March.

Tip: Give it acid, wet soil and water only with rainwater: it will grow larger and finer every year. Plant it where you can see the cinnamon-brown fertile fronds well in April–May.

Cinnamon fern: when to prune it?

Pruning months: March and June.

When: In March remove the old fronds, before the new croziers unfurl. In June, optionally, the withered fertile fronds.

How:

• In March cut the dead, brown fronds off just above the crown.
• In June cut the withered fertile fronds off at the base if you want a tidier clump.
• Work carefully around the woolly croziers in the centre: they are the new fronds.

Caution: Do not cut off the young cinnamon-brown fertile fronds in spring: they are its main feature.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

Only for old, large clumps with several crowns: in March–April cut off a piece with a crown and roots using a sharp spade or saw. The roots are tough; replant at once and keep wet.

Spores

The green spores remain viable for only a short time. Sow them in May–June straight after collecting on sterile, moist, acid compost under glass; small ferns appear after a few months.

Cinnamon fern: how does it get through the winter?

Hardy to −35 °C.

• Very hardy, to about −35 °C: no protection is needed in Belgium.
• In autumn the fronds turn yellow to orange-brown and then die back; the plant regrows in spring.
• Leave the old fronds until March: they protect the crown and croziers.
• In a pot: keep the compost moist, stand the pot in shelter and wrap it in hessian during severe frost.

Diseases and pests

• Brown fronds: Dry, brown frond edges in summer from dry soil or fierce sun. Water generously with rainwater, mulch or move it to a wetter spot.
• Yellow fronds: Pale, yellow fronds in limy soil or from limy tap water. Use rainwater and acid leaf mould.
• Late frost: The young croziers can freeze in April. Cover with fleece if frost is forecast; the plant usually regrows.
• Slugs: Sometimes eat the young croziers. Pick them off in the evening, or lay a plank as a hiding place and clear them in the morning.

Through the year

• March: Cut off the old fronds. Spread acid leaf mould.
• April: Woolly croziers appear. Plant or divide.
• May: Cinnamon-brown fertile fronds. Sow fresh spores.
• June: Remove withered fertile fronds. Water in dry spells.
• July: Water in dry spells, ideally with rainwater.
• August: Water in dry spells.
• September: Plant.
• October: Autumn colour yellow to orange-brown. Plant.
• November: The fronds die back. Leave them standing as protection.

Did you know?

• It was long called Osmunda cinnamomea, but DNA research showed that it forms a separate lineage; that is why it is now called Osmundastrum.
• Its spores are green and remain viable for only a short time, unlike the spores of most other ferns.
• It belongs to a very old group: fossils of almost identical ferns are tens of millions of years old.