Rustyback fern

Sun

Partial shade is safest. It tolerates sun in cooler climates when its roots are sheltered in a rock crevice; protect it from strong afternoon sun in hot climates.

Water

Water regularly while establishing, allowing excess water to drain freely. Established plants tolerate dry spells, but prolonged drought makes the fronds curl and growth stop.

Soil

Gritty, sharply drained, neutral to alkaline soil with some leaf mould. Particularly suited to limestone crevices; avoid wet, compacted soil.

Height

0.3-0.7 ft (0.1-0.2 m)

Spread

0.3-0.7 ft (0.1-0.2 m)

Foliage

Evergreen. Short, leathery, green fronds with rounded lobes and dense rusty-brown scales on the undersides. Fronds curl inward in dry weather, exposing the scaly backs.

Growth

Slow

Care needed

Low

• Deer resistant
• Drought tolerant
• Heat tolerant
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   0.5 ft (0.15 m)

   full size

About 5 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Native to

the UK

Growth rate

Slow

• Plant in a roomy rock crevice or gritty soil pocket, keeping the crown at the surface.
• Water new plants during dry spells until their roots are established.
• Keep drainage outlets clear and avoid sites that stay wet through winter.
• Do not bury the crown under bark mulch or fallen leaves.
• Usually no feeding is needed; avoid rich compost and strong fertilisers.

Pruning. In spring, snip off dead or badly damaged fronds at their bases without cutting emerging growth. Leave curled but living fronds alone: they may reopen after watering.

Spring

Plant into a prepared, sharply drained crevice and water thoroughly.

Spring

Remove dead fronds carefully as new growth appears.

Summer

Check new plants during dry weather and water their root pockets when dry.

Autumn

Remove fallen leaves that cover the crown or block drainage.

Winter

Check that pots and planting pockets drain freely; move containers out of persistent rain if necessary.

• Tuck into limestone wall crevices for small patches of evergreen texture.
• Plant in an alpine trough with other lime-loving rock plants.
• Use in a partly shaded rock garden where its curled, rusty-backed fronds can be seen closely.
• Combine with other small wall ferns in separate crevices for contrasting frond shapes.

Garden styles it suits: Alpine rock garden, Dry gravel garden, Cottage garden, Cotswold cottage, Mediterranean and Small-space.

Plant it with: Wall-rue, Maidenhair spleenwort, Fairy foxglove and Encrusted saxifrages.

Wildlife: Rock crevices around the plant provide shelter for small invertebrates. As a fern, it produces no flowers, nectar or pollen.

• Crown or root rot in wet soil: improve drainage and replant in a gritty pocket with the crown exposed.
• Scorched fronds in intense sun: provide afternoon shade, especially in hot climates.
• Prolonged drought causing tightly curled fronds: water the root pocket thoroughly if you want active growth; curling alone does not mean the plant is dead.
• Slugs and snails damaging young fronds: inspect during damp evenings, remove them by hand and clear nearby hiding places.

Not known to be toxic to people, cats, dogs or horses. Species-specific information on ingestion is limited, so do not treat the fronds or rhizomes as food or allow pets to eat substantial amounts.

• Wall-rue (Asplenium ruta-muraria)

  Wall-rue has divided fronds with separate wedge-shaped leaflets, rather than the rustyback's broad, rounded lobes and densely scaly undersides.

• Maidenhair spleenwort (Asplenium trichomanes)

  Maidenhair spleenwort has small, separate leaflets arranged along a dark, wiry stalk; rustyback has broader, closely joined lobes and rusty scales beneath.

The common name refers to the rusty-brown scales covering the undersides of the fronds.

Propagation. Grow from spores sown on a moist, clean, lime-containing fern-growing medium under cover; development is slow. Established clumps with several crowns can sometimes be divided carefully in spring, but small plants are best left undisturbed.

Accepted botanical name

Asplenium ceterach

Native range

Afghanistan, Albania, Algeria, Austria, Baleares, Belgium, Bulgaria, Corse, Cyprus, Czechoslovakia, France and Germany.

Measured

Soil pH 7.5 to 8. Average height 14 cm.

Sources: GBIF (CC BY 4.0) and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.