A selection of Blechnum and other ferns

Hardy Blechnum in cultivation Many species of hard fern are hardy but only a few are widely grown. Tim Pyner has trialled a broad range in his garden and discusses those that are valuable additions to the palette of evergreen ferns

lechnum provide some known but a wider selection is grown Classification and morphology of the best-known and most by enthusiasts. Many of these lesser With around 200 species, Blechnum Buseful ferns in cultivation. known species make attractive is the largest genus in the family Commonly known as hard or water garden plants. Blechnaceae. Most species occur ferns, the tough, evergreen fronds In this article I will discuss the in the southern hemisphere. The are architecturally pleasing and most worthwhile species that I have family includes 7 or 8 other genera, create an effective background to found to be winter hardy over a Woodwardia and Doodia being the often colourful young croziers. number of years in coastal Essex, frequently cultivated. Recent Only a handful of species are well plus a few others grown elsewhere. molecular studies have placed

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size with tough evergreen foliage, colourful new growth and easily cultivated. Many of these species have previously been classified as B. capense, but this name is now restricted to African plants. Plants from South Africa are supposedly in cultivation, but the vast majority in gardens will be one of the following.

n Blechnum chilense (syn. B. cordatum) This well known species is deservedly one the most popular garden ferns. It is unfortunate that two names are in current use.

RHS Herbarium Blechnum cordatum has priority but Blechnum chilense is one of the largest of the cultivated species and can form extensive colonies there is some doubt regarding its conspecifity with B. chilense. I have Blechnaceae in a group of families that Blechnum chilense group chosen to use B. chilense, not least includes Thelypteridaceae, Onocleaceae These species have strong and because Australasian species in this (Schuettpelz & Pryer 2008) and creeping rhizomes, robust and fully group have been subject to careful Athyriaceae (Christenhusz et al. 2011). pinnate dimorphic fronds, and revisions that have resolved their Blechnum itself requires further study pinnae that are shortly stalked, taxonomy and recognized additional and generic changes are certain to strongly veined and toothed. The species. Recent authors (e.g. Kessler occur in the future (Smith et al. first four species have the lowest et al. 2007) consider a detailed study 2008, Christenhusz et al. 2011). pinnae on the frond not or hardly of the species complex in South The stems of Blechnum are woody shorter than those above. The other America is required. Blechnum chilense RHS / Tim Sandall rhizomes, creeping or erect, two species have lower pinnae that in the narrow sense is native to sometimes forming trunks. The decrease in size down the frond. temperate South America and can fronds are pinnate or pinnatifid. The various species range be abundant in high rainfall areas. The frond stalk (stipe) is scaly to throughout temperate regions of the In ideal conditions this some degree as is the frond midrib southern hemisphere. They are magnificent species can produce (rachis). The leaflets (pinnae) can among the most useful ferns for fronds reaching 150cm long and be stalked or sessile (adnate). The gardens, being of moderate to large 30cm wide. The new fronds are spores are borne on specialized reddish, maturing to dark green. fronds known as fertile fronds (the The stipes are clothed with broad, normal fronds are referred to as brown scales and the pinnae tend to sterile fronds) . The sterile and have strongly wavy margins. In large fertile fronds can be similar in gardens old plants of B. chilense can appearance (monomorphic) or form impressive colonies that differ (dimorphic). Most of the dominate extensive areas. hardy species bear dimorphic fronds. n Blechnum wattsii In this article I have attempted This species, native to eastern to group the species discussed Australia, is surprisingly hardy. It using characters that show natural superficially resembles B. chilense but relationships. However, in some is lower growing, with fewer, flat cases the characters are superficial. pinnae. The young fronds are ➤ Unless stated, frond descriptions Blechnum wattsii showing sterile fronds on the left

refer to the sterile fronds. otherwise stated unless Simon Garbutt by All photographs and a fertile (spore-bearing) frond on the right

March 2012 37 genus profile Tim Pyner Tim Blechnum procerum (left) takes on deep orange-brown hues (centre) in winter. The fronds of B. minus (right) are orange to pink on emergence in spring reddish and even mature fronds Chambers & Farrant (1998) resolved is native to southeast Australia. It is retain a brownish tint. This is an the taxonomy of the group in New unclear whether similar plants in elegant fern with fronds up to 60cm Zealand and this species was circum­ New Zealand are conspecific. long that is useful in smaller gardens scribed to include the endemic Despite the epithet, B. minus can get where B. chilense may be too vigorous. lowland plants of that country. quite large and old plants often form It is hardy in Essex but remains short trunks. The rhizomes spread n Blechnum procerum small, with fronds of 30–40cm, but slowly and the fronds are glossy, and Native to New Zealand this is a with greater humidity it is much orange to pink when young. The superb garden fern. The sterile larger, up to 120cm. Even small plants fronds are less resistant to cold than fronds have few, rather short, broad produce some of the most colourful other members of the group, but pinnae that are dark, bronze-green fronds of any hardy Blechnum. Bright many colourful new fronds are during the growing season. In winter light is required to develop the quickly produced in the spring. they take on a glorious orange-brown pigments which can range from hue which lights up the area where it bright pink to deep orange. Blechnum magellanicum group grows. The fertile fronds are erect to This group contains some of the around 40cm, contrasting with the n Blechnum minus largest and most beautiful hard ferns. strongly spreading sterile fronds. This is a very attractive species that They can form massive trunks, sometimes 3–4m high in the wild. n Blechnum montanum These large plants may be centuries This fern resembles B. procerum, but old and can form magnificent the fronds, to 50cm, are more glossy colonies. Plants grown in the UK are with curved and tapered pinnae. I smaller but still form striking plants. have not noticed any marked change The fronds are dimorphic, and the in frond colour in winter. It is endemic sterile pinnae are adnate to the rachis to New Zealand at relatively high with only the lowest ones stalked. altitudes and I have found it rather Rudimentary pinnae reduced to slow-growing compared to other small flanges flank the stipes. The species in the group. pinnae margins are entire. n Blechnum novae-zelandiae n Blechnum magellanicum

Until recently, this and the previous Pyner Tim This is the hardiest of the trunked species were confused with B. capense. Blechnum novae-zelandiae species, thriving in most of the UK.

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Blechnum magellanicum (left) is the hardiest of the trunked species, butBlechnum tabulare (right) is less so, seen here on a short trunk

The trunk is stout, reaching 2m in 60cm fronds. Fernández Islands off the west coast the wild. The fronds are large, glossy, Compared to B. magellanicum, the of Chile. Large plants there form pale and rather whitish below, and pinnae are broader, fewer and more magnificent colonies at higher usually 50–80cm in cultivation but widely spaced. The fertile fronds altitudes, both in shade and in the up to 150cm in the wild. The dense also have fewer pinnae, and the open. It has recently become blackish scales on the rhizome and scales are ginger rather than black. available in horticulture and is stipes are stiff and have been In the past, plants as diverse as proving to be fairly hardy in compared to pig bristles. The fronds B. chilense and B. magellanicum have sheltered gardens. Ensoll & Hughes are often coated in stalked glands been included in B. tabulare. This is (2007) describe its cultivation at making them sticky to the touch, perplexing as the plants are clearly Royal Botanic Garden Edinburgh the fertile fronds particularly so. morphologically and geographically and at Logan Botanic Garden on the Blechnum magellanicum is a highly distinct. The name is now restricted west coast of Scotland. A plant in my impressive fern and seeing a group to plants from Africa and islands in garden in Essex is slow and remains of large plants gives a primeval the Indian Ocean. small, so higher rainfall and humidity atmosphere in sheltered gardens. may be beneficial. It is hardly conceivable that, in the n Blechnum cycadifolium This species resembles B. magellan­ past, this and B. chilense have been This species is endemic to the Juan icum but has shorter fronds to 100cm. treated as a single species as they The young fronds are densely scaly differ substantially. on the lower surfaces and the scales are bright golden-brown. If this n Blechnum tabulare species proves to be consistently The least hardy member of the hardy it will become a wonderful group, young plants of this species addition to British gardens. will struggle to survive an average UK winter without protection. Even n Blechnum palmiforme large plants lose their fronds through Very recently introduced, this moderate winters and are slow to exciting species from Tristan da recover. With protection, young Cunha and nearby islands in the plants grow quickly but will not southern Atlantic Ocean is showing produce trunks for many years. great promise in Scottish gardens. However, trunkless specimens make It has proved cold-hardy through extremely handsome ferns with Blechnum cycadifolium recent winters in Scotland ➤

March 2012 39 genus profile RHS / Carol Sheppard RHS / Carol Blechnum nudum (left) is the Australian counterpart to New Zealand native,Blechnum discolor (centre). Blechnum spicant (right) is a northern hemisphere species

(J. Taggart, pers. comm.). Taggart that are only lost in the harshest species the sterile fronds are (2009) gives an excellent account winters. In the UK plants tend to spreading and gradually narrow and description of the fern, including form large clumps, but in more towards both ends. The sterile details of its native habitat and favoured areas huge colonies can fronds are narrow and erect. introduction to Scotland. develop, as for example in the It resembles B. cycadifolium but Parque da Pena, Sintra, Portugal. n Blechnum spicant has shorter pinnae and blunt fronds This beautiful evergreen species reaching 80cm in length. n Blechnum discolor often carpets woodlands, stream This the New Zealand counterpart banks and rocky gorges in the west Blechnum nudum group of B. nudum; both have been confused and north of the UK. Even in the Species in this group are medium- in the past although they are quite drier southeast it grows well in sized ferns native to Australia and distinct. Blechnum discolor forms well- sheltered woodland. It is native New Zealand that can produce short defined shuttlecocks and the frond throughout Europe and western trunks in humid habitats. In the UK, lower surface is very pale, sometimes Asia, and also western North trunked crowns are liable to be killed almost whitish. The sterile pinnae America. Hard fern makes in hard winters but new crowns re- are broader and their apices are more a wonderful garden plant given grow from the base. obtuse. The fertile fronds are even sheltered, acidic, conditions and more distinctive: the lower pinnae can eventually form large clumps. n Blechnum nudum being basally expanded at the rachis The fronds are dark green and up This species is native to eastern giving a unique and readily to 5cm wide, while the fertile ones Australia. The fronds can reach 1m recognized appearance. The ginger are longer than the sterile, reaching but are usually no more than half this scales on the fertile fronds are hair- about 45cm in length. length. The undersides of the sterile like and relatively abundant. fronds are pale green and the stipes When well-grown this is one of n Blechnum niponicum and lower part of the rachis are the most beautiful ferns. However, it This Japanese species is closely blackish. The fertile fronds have can lose fronds in moderate winters related to B. spicant but has broader crowded narrow pinnae that are not and this will prevent plants reaching sterile fronds, up to 10cm wide and expanded at the base. The scales on their full potential. 40cm long. The new fronds are the fertile fronds are broad, pale and heavily tinged pink and mature a rather sparse. Blechnum spicant group paler green than those of B. spicant. It is a very attractive species The well-known UK native hard fern This is a very attractive species but producing many fronds each summer belongs to this group. In both remains small in my garden.

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Blechnum australe subsp. australe (left), Blechnum hastatum (centre) and Blechnum penna-marina subsp. penna-marina (right)

Blechnum australe group somewhat dimorphic. It is not as Blechnum penna-marina group Species in this group occur in South attractive as subsp. australe because These species are low-growing with Africa and South America. They the new fronds are green. strongly creeping rhizomes forming have creeping rhizomes that can large patches. The narrow fronds are form substantial colonies. The n Blechnum hastatum strongly dimorphic, sparsely scaly fronds reach about 40cm in length This species is from western South and taper towards the base. The and are pinnate at the frond base America, mainly Chile but also pinnae are sessile. with the pinnae gradually becoming Argentina. The most obvious diff­ adnate towards the apex. The pinnae erence from B. australe is the almost n Blechnum penna-marina are falcate, basally expanded and monomorphic fronds: the fertile This species is well-known in gradually reduce in size towards the ones have broad areas of sterile tissue cultivation and widely available. It frond base. The pinnae margins are bordering the indusia. The new fronds occupies a cool temperate range in minutely denticulate. are green and the broad pinnae help the southern hemisphere. Its The close relationships between create an attractive ground cover. taxonomy has recently been revised the species can cause problems with This species seems hardier than (Chambers & Farrant 1996) and identification. Typical B. australe B. australe and the fronds remain divided into four geographical and B. hastatum are distinct, however wintergreen at low temperatures. subspecies, two of which are B. australe subsp. auriculatum is commonly grown. somewhat intermediate. Blechnum penna-marina subsp. penna-marina is native to South n Blechnum australe America and some South Atlantic The typical subspecies, subsp. islands. It has pinnae that tend to australe, is native to southern Africa. overlap and the stipe is dark The fronds are dimorphic, and it is purplish-black with this colour the most attractive fern in this group extending into rachis. This as the young fronds are tinged with subspecies tends to be one of the pink and orange. tallest, with fronds to 30cm long. The South American variant, They are less glossy than those of subsp. auriculatum, is found in eastern subsp. alpinum and the pinnae are South America from south Brazil to usually rounded at the apex. Argentina. It approaches B. hastatum Blechnum penna-marina subsp. in some characters but the fronds are Blechnum penna-marina subsp. alpinum alpinum occurs throughout most ➤

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are in cultivation. Blechnum mochaenum var. mochaenum is from mainland South America. Its fronds are rather thick and glossy and reach 35cm in length. The stipe is relatively stout and at least 1mm in diameter. Blechnum mochaenum var. fernandez­ ianum is from the Juan Fernández Islands. The fronds are smaller, to 15cm long, and of a thinner texture. The stipe is under 1mm in diameter.

Other species n Blechnum chambersii Tim Pyner The rhizome of this species is erect, giving rise to a rosette of sterile Blechnum microphyllum (left) and Blechnum mochaenum var. mochaenum (right) fronds to 35cm in length that spread horizontally. The pinnae are slightly of the range of the species and is the other plants. The rhizomes do not falcate, strongly veined and sharply only subspecies found in Australasia. form dense mats and tufts of fronds toothed. The fertile fronds are erect, Its pinnae tend not to overlap and will arise, scattered around the around the same length as the sterile the stipe is dark reddish brown at original planting. The fronds, ones, with very narrow pinnae. the base and greenish below the purplish when young, taper towards It is native to forested areas of rachis. It is low growing and quite the base where the lowest pinnae southeast­ Australia and New dwarf. The fronds are 10–20cm long, form semi-circular flanges along the Zealand. Subtly attractive, the dark have a glossy sheen, and the pinnae rachis. The pinnae are strongly green, glossy fronds stand out among tend to be shortly pointed. adnate. The fertile pinnae are long, other ferns. It is particularly suited Both subspecies make attractive narrow and strongly falcate. The to damp, shaded areas. groundcover with reddish or species seems hardy although fronds purplish young fronds but can be can be scorched in winter. Two n Blechnum fluviatile invasive, especially on peaty soil. varieties are recognised and both This wonderful species is a personal n Blechnum microphyllum (syn. B. gayanum) Chambers & Farrant (1996) consider this to be a subspecies of B. penna- marina. However, in cultivation it is very distinct and I prefer to treat it as a species. It is a delightful, well- behaved, miniature species, slow growing with short rhizomes and orange new fronds. The pinnae are narrowed at the rachis and strongly toothed. The fronds are usually no more than 15cm long. n Blechnum mochaenum This quietly attractive rhizomatous species from south Chile and Argentina slowly creeps among The glossy fronds of Blechnum chambersii make it conspicuous in most garden situations

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growing in ideal conditions. Acid to neutral soils are essential and plentiful organic content is beneficial. Most species prefer shade, however those with colourful new growth often produce more intense tones in bright light. Most species remain wintergreen above -5°C. Some will lose their fronds at lower temperatures but generally recover quickly the following summer. Dead and damaged fronds are best removed in the spring to allow colourful new growth to be clearly visible. Exposed trunks of some species are vulnerable to drought in summer and cold in The unfurling fronds of Blechnum fluviatile are caterpillar-like and it will slowly form a colony winter. A mulch around exposed trunks is beneficial under both favourite. It is native to New fascinating to watch these fronds, conditions. Zealand and southeast Australia and, resembling large hairy caterpillars, Propagation by spores can be slow despite growing naturally on wet gradually unfurl over a couple of or erratic (Olsen 2007). Species with stream banks, is easy to grow in a days. The fertile fronds are very creeping rhizomes can be easily shady spot that does not dry out. narrow and erect. Shortly rhizom­ divided in spring or early summer. Older plants may produce short atous, it will slowly form a colony. trunks. The narrow, horizontally Conclusion spreading, sterile fronds to 40cm Cultivation Blechnum display a combination of long are furnished with rounded, Blechnum prefer high rainfall and dramatic, colourful young fronds dark or apple green pinnae. These humidity and will grow best in such against a backdrop of dark green contrast beautifully with the dark situations. They can only grow well mature foliage. This allows them to rachis which is densely coated with in drier areas if irrigated, and even be considered an essential compon­ spreading black scales. It is then will not attain the size of plants ent of gardens where structure, form and foliage effect is a priority. references & bibliography My selection of species here is Chambers, TA & Farrant, PA (1996) (Blechnaceae, Pteridophyta) from inevitably rather subjective and Four subspecies of the fern Blechnum Bolivia. Amer. Fern J. 97(2): 66–80 additional species are certainly penna-marina (Blechnaceae: Pteridophyta). Olsen, S (2007) Encyclopedia of Garden Fern Gazette 15(3): 91–100 Ferns. Timber Press, Portland, Oregon grown in British gardens. I would Chambers, TA & Farrant, PA (1998) Schuettpelz, E & Pryer, KM (2008) be grateful to receive further The Blechnum procerum (“capense”) Fern phylogeny. In: Ranker, TA & information on their performance. (Blechnaceae) complex in New Zealand. Haufler, CH (eds)Biology and Evolution New Zealand J. Bot. 36: 1–19 of Ferns and Lycophytes. Cambridge Tim Pyner is a keen plantsman, Christenhusz, MJM, Zhang , X-C University Press, Cambridge particularly interested in ferns and & Schneider, H (2011) A linear Smith, AR, Pryer, KM, Schuettpelz, trialling tender plants outdoors. sequence of extant families and genera E,Korall, P, Schneider, H & Wolf of lycophytes and ferns. Phytotaxa 19: PG (2008) Fern classification. In: email: [email protected] 7–54 Ranker, TA & Haufler, CH (eds) Ensoll, A & Hughes, K (2007) Cultiv­ Biology and Evolution of Ferns and acknowledgements ation and hardiness notes for Blechnum Lycophytes. Cambridge University Many thanks to Martin Rickard, cycadifolium. Sibbaldia 5: 87–92 Press, Cambridge Jamie Taggart, Michael Hayward, Kessler, M, Smith, AR & Lehnert, Taggart, J (2009) Gough Island tree Andrew Leonard and Sylvia M (2007) Ten new species and two fern comes to Scotland. Pteridologist Martinelli their generous help in the new combinations of Blechnum 5(2): 92–94 preparation of this article.

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