Hardy Blechnum in Cultivation Many Species of Hard Fern Are Hardy but Only a Few Are Widely Grown
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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 36 March 2012 PlantsmanThe 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 RHS / Tim 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. 38 March 2012 PlantsmanThe 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.