Ferns

These forgiving foliage plants offer lasting colour and texture indoors and out, says Miranda Kimberley.

Nephrolepis exaltata 'Bostoniensis'. Image: Garden Picture Library
Nephrolepis exaltata 'Bostoniensis'. Image: Garden Picture Library

Ferns last experienced a boom in popularity in the "pteridomania" of the mid 19th century. Yet their intricate and subtle leaf forms can also provide a coolly contemporary look.

While they usually fill shady spots, there are many types of ferns that suit different aspects. After all, there are 12,000 species whose life cycles differ to flowering plants and conifers in that they produce spores rather than seeds.

They range from tiny aquatic to terrestrial ferns with their fronds emerging from a crown or rhizomes to the majestic tree ferns that have become popular in landscaping. Many grow in woodland settings, but there are also ferns that grow in full sun, in sand, on rock and submerged in water.

The UK trade in ferns encompasses several types. There are the tender varieties, which need temperatures between 0 degsC and 10 degsC and therefore are marketed as house plants, such as the Boston fern Nephrolepis exaltata Award of Garden Merit (AGM). There are also the hardy ferns, which are good garden plants - many are native British species or bred from them. Then there are the special larger types such as tree fern Dicksonia antartica or Blechnum chilense, which grows to an imposing 1.2m.

Hardy, terrestrial ferns should be planted in open, free-draining soil. Because ferns generally have fibrous roots they prefer the looser soil, made so by incorporating organic matter such as well-rotted compost or leaf mould. However, as they do not need energy for flower or seed formation, ferns do not require fertilising and actually die back if over-fertilised.

Most ferns prefer shade but there are some that can do well in sun, such as Blechnum chilense or Dryopteris cycadina AGM. Once planted, ferns prefer to be left alone to mature and spread. Their dead fronds can be cut off in spring and an occasional mulch applied. Division will set back their growth.

Indoor ferns, like their hardier cousins, also tend to like damp conditions and dislike full sun, although most will tolerate a few hours in early morning. The kitchen and bathroom can be the best places to grow them, being more humid than other rooms. Elsewhere, standing plants on a saucer of damp pebbles or gravel will create a humid microclimate. They can be given a weak liquid feed once a fortnight.

Retailers should be careful when buying tree fern species Cyathea and Dicksonia. They are both listed in CITES, the convention governing the trade in endangered plants and animals, and retailers should ask to see evidence of their provenance and check they have been grown under licence before buying.

WHAT THE SPECIALISTS SAY

- Steven Fletcher, owner, Fernatix, Suffolk

"The reason people like ferns is because they are incredibly resilient. Even if the fronds dry out and die, new ones will come back the following year. They are generally pest free and don't get attacked by slugs, like Hosta. They can be put in a shady or semi-shady spot and just forgotten. There are lots of different varieties and colours.

"I'm commonly asked for ferns that suit dry shade. Dryopteris is a good genus for that aspect - they are tough, resilient and evergreen. I used to think that they were dull but they are excellent garden plants.

"If the garden is reasonably damp then the most popular choice is the Japanese painted fern, Athyrium. There are so many different varieties - including 'Pewter Lace', 'Burgundy Lace' and 'Silver Falls'.

"It may be controversial, but I think tree ferns have probably had their day. They can go down to -6 degsC or -7 degsC, but this winter we saw temperatures down to -10 degsC in the coldest winter for 30 years, so a lot of people will have lost them.

"After all, they are southern hemisphere plants not native to this country and are not as tough as a lot of nurseries make them out to be. I don't know whether many people will have wrapped them in fleece."

- Ben Kettle, director, World of Ferns, Gwynedd

"Ferns are popular because there is a huge variety of forms, colours and patterns. They are tactile, sexy plants. Generally the most popular hardy genera in retail include Dryopteris, Athyrium, Polystichum and Blechnum.

"We are always introducing new varieties. One of these is Araiostegia parvipinnata, from south-west China and Taiwan. It is related to Davallia but is a giant in comparison. Another great new fern is Woodwardia orientalis var. formosana, one of the Chain Ferns. It has flat, glossy fronds and is stronger than Woodwardia unigemmata.

"Blechnum chilense is currently very popular, with its bold, leathery fronds that are deep red when new but turn green. I also like Doodia media and the slightly larger D. squarrosa. Caring for ferns really depends where they originate from - some need quite a lot of care, but not the hardy varieties."

IN PRACTICE

- Verity Guise, planteria supervisor, Batsford Garden Centre, Gloucestershire

"We focus on the hardy outdoor types, including Asplenium, Polystichum, Dryopteris and Athyrium. Certain types, like the Athryium species and varieties, need more moist conditions and shelter from the sun.

"However, others such as Asplenium can withstand drier conditions. They are quite tough varieties and they can even be grown in rockeries. To show off our range of plants we have a fernery, where the ferns grow among pieces of wood and moss."

SPECIES AND CULTIVARS

Hardy, outdoor types

- Athyrium filix-femina AGM, known as the lady fern, is a tall, upright, deciduous species growing to 1.2m. Suited to woodland planting, it is one of the most attractive native ferns and has many cultivated varieties.

- A. niponicum var. pictum AGM, the Japanese painted fern, has bipinnate fronds that are silver greyish green with mauve midribs. A deciduous type that likes moist conditions. Minimum temperature -15 degsC. Again, many cultivars.

- Blechnum chilense is a large fern, growing up to 1.2m, with leathery, matt green fronds that are deep red when young. An evergreen type that likes moist conditions. Minimum temperature -15 degsC.

- Cyathea australis, the rough tree fern, grows up to 6m tall in cultivation. It has broad triangular fronds, with conspicuous leaf-bases that are rough with blunt spines. An evergreen type that likes damp conditions. Minimum temperature -5 degsC.

- Dicksonia antarctica is the most popular and widely available tree fern species in the UK. Copes with temperatures down to -10 degsC. Specimens have survived the winter outdoors in Britain but recent winter temperatures may have been too bitter. Giving them a sheltered position and extra insulation during cold spells is recommended.

- Dryopteris filix-mas AGM is a hardy British native, also known as the male fern. It has elegant but fairly robust foliage. Able to cope with a sunnier site and drier soil than most hardy ferns, it is classified as deciduous but in mild climates the foliage may remain all winter. Grows up to 90cm.

Indoor types

- Adiantum capillus-veneris, the maidenhair fern, is a familiar house plant. The deciduous fronds unfurl a delicate purplish-pink, but end up mid-green. Likes dry conditions, minimum temperature 0 degsC.

- Asplenium bulbiferum hybrids are bred from a species originating in New Zealand and Australia. The fern has tripinnate oval fronds that produce bulbils. An evergreen type that needs a minimum temperature of 0 degsC and likes dry conditions.

- A. nidus AGM, the bird's nest fern, is a tropical variety that is used as a house plant. Has simple, upright, bright green fronds. It is evergreen and likes dry conditions. Minimum temperature 10 degsC.

- Nephrolepis duffii is known as the fishbone fern because of its small, rounded pinnae along the frond midrib that resemble a fish skeleton. An evergreen type that likes dry conditions. Height 30cm. Minimum temperature 10 degsC.

- N. exaltata 'Bostoniensis' is a new variety whose parent species is already in widespread cultivation. It has attractive arching, lance-shaped pinnate fronds. An evergreen type that likes to be kept dry. Minimum temperature 0 degsC.

- N. falcata is a tropical species from Malaysia that needs a minimum temperature of 10 degsC. Known as the giant sword fern, it produces lance-shaped, pinnate fronds, with widely spaced pinnae. An evergreen that likes to be kept dry.

- Platycerium bifurcatum AGM is the dramatic staghorn fern. As its name suggests, the fronds are flat and deeply lobed, resembling a stag's antlers. Best fastened to bark with wire and sphagnum moss rather than potted. Minimum temperature 0 degsC.

- Polypodium subauriculatum 'Knightii' has weeping feathery fronds, with deeply incised pinnae. It is a large fern - its fronds reaching up to 2.4m long - making for an imposing potted plant. An evergreen type that likes damp conditions. Minimum temperature 0 degsC.


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