The unfurling of exquisite fern crosiers into delicate emerald fronds intermixed with bluebells is a welcome sight in spring along the banks and ravines of my local woodland. Here in the nearby woods, the ferns are majestic in form and fully complement the bluebells and other delicate spring flowers. But in many gardens ferns are missing, often perceived to be difficult to grow and uninteresting to look at.
Their delicate shape and structure certainly holds more than enough interest for me. Ferns are simply beautiful plants. In some cultures ferns are highly prized for their appearance and as a food source. The Maori often feature ferns in their art, carving and tattoos and the Maori word ‘koru’ means loop. This loop shape is based on an unfurling silver fern frond. It is highly symbolic in Maori culture and represents new life, growth, strength and peace. The spiral shape denotes continuous movement and the centre suggests a return to the origin. It is a symbol found on the New Zealand flag and the symbol of New Zealand’s famous All-Blacks rugby team.
The fern lifecycle
Belonging to the division of plants called pteridophytes, ferns are vascular plants that produce spores. They are botanically pretty interesting because they do not reproduce in the way most horticulturists are familiar with. There is an absence of conspicuous flowers and fruit, instead they use spores often in huge quantities. The plants usually alternate between haploid (one single set of chromosomes) and diploid (two sets of chromosomes – one from each parent) generations in the form of gametophytes and sporophytes. The gametophytes can be male, female or both and produce the cells for sexual reproduction. The sporophyte produces spores that in turn produce the gametophyte.
In brief, the sexual cycle involves the production of spores on the sporophyte, which are shed and grow into gametophytes, also often called the prothallium. When the conditions are right, mature sperm are released from the antheridium and swim to the egg-producing part called the archegonia under the gametophyte's underside. When fertilisation occurs a zygote forms, which develops into an embryo and eventually outgrows the gametophyte to become the sporophyte.
Alternatively, many ferns will reproduce vegetatively by branching of the underground root stem or rhizome. Some do this by root proliferations and others in the wet tropics by leaf proliferations. In fact, ferns are so diverse in their reproduction that some are termed apomictic, that is they will produce spores that have the same number of chromosomes as the sporophyte, so new sporophytes can arise from cells of the gametophyte without the need for gametes.
The diverse world of ferns
Ferns are extremely varied in their appearance and habitats. They occur all over the world and are also prolifically evident in the fossil record. Being extremely versatile plants, ferns will accommodate any number of different sites from boggy patches to dry shade. For gardeners, there is a limitless choice of different varieties to choose from.
Colin Ward from Swinesmeadow Farm Nursery in Peterborough has been fascinated by ferns for many years and grows over 60 different varieties. The nursery stocks other exotic and rare plants but Colin has keen interest in ferns.
“I spent my childhood in Hong Kong where I was immersed in the local flora and this gave me a passion for exotics including bamboos, palms and of course ferns,” said Colin. “I am a complete and utter plantaholic but ferns are something special.”
He considers them essential in any garden to enhance the structure, form and colour of other plants like for instance hellebores, bamboos and Arisaema. As long as there is a good contrast between different fern varieties they can be very successfully planted together. Another good use of ferns is as a foil to spring bulbs like snowdrops adding an extra layer of interest. Their uses are not limited as there is a vast range of species and varieties, which suit many different situations offering substantial scope for gardeners.
Colin grows many of the ferns that are sold at Swinesmeadow Farm Nursery. Fern propagation can be tricky but the key to success is moisture. Collecting spores involves picking fronds and placing in them in brown paper bags and leaving them for a few days somewhere cool and dry. After a couple of weeks the spores will have separated away from the frond but careful sieving is still needed to separate out the leaf debris. Some gardeners use a fine potter’s sieve to achieve this.
Colin explains, “Picking the right time for collecting spores is crucial. The sporangia which are the structures containing the spores, need to be fully ripe.”
Once the spores are collected, they need to be sown. Using fine grade compost and boiled water, make a substrate soup in a suitable container (takeaway tubs with lids are ideal) and leave to rest. This is important to eliminate any rogue spores and other weed species. After 24 hours sow the fern spores over the surface and pop a lid on. Containers can then be stacked in a cool greenhouse and left, as the condensation from the lids will keep the substrate moist. Once the young fern plants appear and they are large enough they can be carefully pricked out. Ferns that can be reliably propagated from spores include Adiantum and many Blechnum species.
“All that’s needed is patience once the spores have been sown,” added Colin. “Sometimes I can often wait 5 years for certain fern spores to germinate. Unfortunately this is normally the fern species that are more interesting.”
Ferns can also be propagated vegetatively or by division. Vegetative propagation is easy to do and can be very successful with many species. Many ferns will produce plantlets or bubils either along the frond rib or at the ends of fronds that will form into new plants. Selected fern fronds can simply be cut and laid on suitable compost, pegged with wire and then half buried with the substrate. The Woodwardia genus responds well to this form of propagation. With some species, bubils can be carefully pulled away from the frond and planted up. Polystichum setiferum Divisilobum Group can be easily propagated in this way.
Colin’s pick of the best ferns
Here is an extensive list of varieties favoured by Colin:
Adiantums: This genus can be slightly tricky to cultivate. Prefers humus rich, moist and well-drained sites.
Adiantum hispidum – A lovely maidenhair fern with dark rib and delicate green fronds. Prefers full shade. If soil conditions are good then it may overwinter.
Adiantum capillus-veneris – A maidenhair fern with black rib. Needs a sheltered site to overwinter outdoors.
Adiantum venustum – The Himalayan maidenhair fern and one of Colin’s favourites. Lovely lime green fronds. Needs a cool humid shaded sheltered spot with moist soil. Deciduous in winter. Good growing in walls.
Aspleniums: A genus with very robust hardy varieties. Provide interest and good form in winter and spring.
Asplenium scolopendrium ‘Angustifolia’ – A good variety with prickled and narrow fronds. Needs partial or full shade.
Asplenium scolopendrium ‘Furcata’ – Another good variety with highly lobed fronds and crispy ends. Needs full shade and free draining soil. Will grow in dry stonewalls.
Asplenium scolopendrium ‘Cristatum’ – This is described by Colin as the ‘lettuce one’. It has a lovely frilly habit. Needs partial or full shade.
Asplenium trichomanes – A delicate looking fern. Needs partial shade and good drainage.
Asplenium australasicum – Commonly known as the bird’s nest fern. A large structural fern with big fronds. Needs moist free draining soil.
Asplenium bulbiferum – Also known as the hen and chickens fern. Finely divided fronds with plantlets produced on upper surface of fronds. Needs partial shade and moist free draining soil
Athyriums: A large genus of deciduous ferns. All require moist soil and partial or full shade. Hardy, tough and easy to grow.
Athyrium nipponicum ‘Pictum’ – Known as the Japanese painted fern. Beautiful silver/pink/purple/green fronds. Needs humus rich soil. It can cope with sub zero temperatures down to about -18°C.
Athyrium nipponicum ‘Regal Red’ – A variety with pretty pale red fronds and darker ribs.
Athyrium nipponicum ‘Silver Falls’ - Another lovely variety with silver fronds, maroon midribs and cascading habit.
Athyrium nipponicum ‘Ghost’ – A stunning variety with pale silvery fronds.
Athyrium otophorum ‘Okanum’ – This has silvery pale green fronds with red flushed mid rib. Delicate colour and very tactile fronds.
Athyrium filix-femina ‘Dre’s Dagger’ – This is unusual in form with crossed deep green frondlets on the main fronds and beautiful crested ends.
Athyrium x ‘Ocean’s Fury’ – This is a hybrid. Silvery green fronds with crested ends like surf on an ocean. Does not like pots. Needs humus rich soil.
Blechnums: This genus is known as the hard ferns. Mainly from the tropical and warm temperate regions. They prefer moist conditions, acid to neural soils and full shade.
Blechnum spiccant – More commonly known as the ladder fern. A good evergreen fern but it can be picky. Fronds are dimorphic, that is the sterile fronds are very different from the spore bearing fronds. Needs moist lime free soil.
Blechnum brasiliense – Known as the dwarf Brazilian tree fern. Beautiful shuttlecock form and fine fronds. Not hardy but will tolerate a cold greenhouse.
Blechnum brasilinense ‘Volcano’ – This variety has beautiful red emerging fronds, which turn green on maturity. Will form a small trunk with height of 30cm. Not hardy but will tolerate a cold greenhouse. Will become deciduous if subjected to really cold conditions.
Tree Ferns: These popular ferns contain a number of different genera mainly from the tropics and sub tropics. They require partial or full shade. Many are not hardy and require winter protection or a cold greenhouse. They need moist soil free draining soil. It is important to not let them dry out over winter.
Cyathea cooperi – More commonly known as the lace fern. This has a lovely form much like a parasol with delicate fronds and really hairy crosiers. It will not tolerate frost.
Cyathea australis – This is known as the rough tree fern. Different in fronding habit to cooperi with a more upright shuttlecock habit. It will not tolerate frost.
Dicksonia antarctica – The very popular smooth tree fern. It can be hardy under good care. Prefers partial shade and needs moist soil. Winter protection is required in all but the mildest areas. It remains evergreen over mild winters. When mature it will survive a frost. For winter protection wrap trunk and to protect crown, stuff with a wodge of straw. Do not allow to dry out over winter. Water at the base and along the trunk. Do not water the crown, as it will cause it to rot.
Dryopteris: Large genera of ferns which are readily available. These are hardy, easy to grow and add interest during winter. They have decorative crosiers emerging in spring.
Dryopteris erythrosora ‘Brilliance’ – A lovely fern with rosy red new fronds and yellowish green fronds in winter. It will tolerate some sun if grown in moist soil.
Dryopteris lepidopoda – An easy to grow evergreen fern from the Himalayas known as the sunset fern. Colourful fronds with hues of orange and gold. Needs moist shade.
Dryopteris austriaca ‘Crispa Whiteside’ – A fern with crisped growth and frilly appearance. Prefers partial shade and moist soil. Semi evergreen.
Dryopteris wallichiana – From the Himalayas and Japan. It has golden green unfurling fronds with dark midrib. Attractive hairy crosiers. Needs moist soil. Dislikes alkaline soils. Reasonably evergreen.
Dryopteris felix-mas ‘Linearis Polydactyla’ – An airy frilly fern with fine foliage. More or less deciduous. It will tolerate dry conditions. It does not like wet ground.
Dryopteris affinis ‘Cristata the King’ – A good large fern with sizable arching fronds, which are finely crested. Prefers moist soil and partial shade.
Dryopteris sieboldii – This species is from Japan. It has lobed (3-5 off main stem) glaucous leathery fronds. It has a completely different frond to other Dryopteris looking more like an Asplenium. Requires shady moist soil and a sheltered spot.
Osmundas: A genus of mainly temperate zone ferns.
Osmunda regalis – More commonly known as the Royal Fern. It thrives along river and streambeds. It is only really interesting once fully mature. Russet tones in autumn. Prefers acid soil and full shade. It will tolerate sun but only under moist conditions.
Polystichums: A large genus of evergreen ferns. Easy to grow in moist well drained soil in partial or full shade. Fully hardy.
Polystichum setiferum – A tough and adaptable fern with a number of different varieties. Semi evergreen until mature. Variety ‘Bevis’ has beautiful filigree like fronds.
Polypodiums: Another large genus of evergreen ferns. Once established it will tolerate dry shade and more open sites. Fully hardy.
Polypodium vulgare ‘Bifido Multifidum’ – A lovely fern with finely divided fronds and crested ends. It looks good in winter and will tolerate dry shade.
Polypodium vulgare ‘Parsley’ – Unsurprisingly the fronds look like parsley!
Onychiums: A small genus of ferns native to the tropics and sub tropics. Beautiful lacy fronds, which look good, contrasted against large leaved plants. Prefers moist well-drained soils and partial shade. Looks good planted on slopes.
Onychium japonicum – Appropriately called the carrot fern. Beautiful airy and lacy fronds. Needs partial shade and a moist sheltered spot. Not fully hardy.
The oddities: This is a list of Colin’s favourite ‘odd-ball’ ferns.
Davallia trichomanoides – More commonly known as the squirrel fern. An epiphytic fern with finely dissected fronds and hairy rhizomes. Fairly hardy. Requires full or partial shade. Needs daily misting during the growing season.
Sphenomeris chinensis BSWJ6108 – A lace fern from the island of Yakushima, Japan and collected in 1998. Delicate fine texture, which forms dense patches of rhizomes. Requires humus rich moist soil and partial/full shade.
Anemia mexicana – This species is commonly known as the Mexican flowering fern. An attractive dimorphic fern with leathery deep green fronds. Needs protection in really harsh winters. Not fussy about soil type but prefers dry shade.
Woodwardia radicans – Also known as the chain fern. A large evergreen fern from the Macaronesian region but also found on other Mediterranean islands. Erect fronds which becoming more arching as they mature. Produces bulbils located at the ends of the fronds. The roots start to develop in the air but when they touch the ground will root into the substrate and form new plants. Prefers partial shade and rich moist soil.
Platycerium sp. – Known as the staghorn ferns. Epiphytic in habit. Evergreen dimorphic fronds. Prefers moist well drained soil. Grow indoors.