genuS profile Woodwardia radicans in a garden in London Tim Pyner surveys Woodwardia chain ferns, a genus of mostly large and in cultivation spectacular species ommonly known as chain most species are colourful, mostly in of elongated segments resembling ferns, Woodwardia are some shades ranging from bronze through a chain of sausages. Cof the most spectacular and to bright red. The young fronds of This article was prompted by imposing ground ferns that can be W. unigemmata and W. prolifera are the realization that two of the grown in temperate gardens. The amongst the most intensely coloured most frequently cultivated species, frond length of European chain fern, of all cultivated ferns. W. radicans and W. unigemmata, have W. radicans, can exceed 3m in its The fertile, spore-bearing fronds few differentiating characters. natural habitats. Ideal growing resemble the sterile fronds in all Without knowing the geographical conditions are not easily replicated species apart from W. areolata. origin of a plant it is sometimes in cultivation but fronds of 2m or Woodwardia radicans and other difficult to decide which species more for this species can be achieved. closely related species usually is being grown. I have therefore The most commonly cultivated produce bulbils or plantlets on checked many herbarium specimens species have erect or shortly the fronds that afford a means at the Natural History Museum creeping rhizomes and leathery, of vegetative propagation. in London, read various papers and winter-green fronds. Two species The name chain fern refers to articles, and visited gardens and fern have far-creeping rhizomes and are the arrangement of the sori. These growers to find reliable characters deciduous, the fronds dying as winter are located close to the midrib of to identify plants grown in British approaches. The young fronds of the frond lobes and are formed and Irish gardens. 184 September 2015 PlantsmanThe Taxonomy The sori of Woodwardia radicans show Recent molecular studies confirm how the genus got its name of chain fern previous hypotheses based on morphology and cytology that Woodwardia belongs to the family Blechnaceae. Cranfill & Kato (2003) demonstrate that the woodwardioid ferns form a monophyletic clade that forms the sister group to the remainder of the Blechnaceae. They recognize 14 species but separate W. areolata and W. virginica into two segregated genera, Lorinseria and Anchistea, respectively. I am persuaded by their arguments for separating these two genera. They cite unique and aberrant morpholog- Species in cultivation form huge stands on steep, forested ical characters, unique cytology, a There appear to be eight or possibly mountain slopes. The large fronds long history of separate evolutionary nine species in cultivation in western arch over and downwards, often existence, and geographical isolation Europe. I discuss the European and resulting in the apical bulbil rooting – both occurring in eastern North Asian species first, then the American when it touches the ground. America. However, for practical species. Within these geographical Most clones withstand frosts to reasons I include them here as groupings they are listed in order of -5°c (RHS hardiness rating H3). species of Woodwardia. frequency of cultivation. Occasionally I have come across All photographs by Tim Pyner unless stated otherwise stated Pyner Tim unless by All photographs Apart from the enigmatic Mexican healthy plants that have survived species, W. martinezii, the remaining European and temperatures briefly down to -10°c species are placed in three sections. Asian species (H4). As it is generally less hardy Most hardy species are in section These species can be recognized by than W. unigemmata the latter is now Woodwardia, and can for convenience the fact that most produce plantlets more commonly planted. be separated into the Old World and or bulbils on the fronds. The thick rhizome is erect or New World groups. Old World ascending and carries large, arched, species are found from the Himalayas Woodwardia radicans evergreen, bipinnatifid fronds of one eastwards to Japan and Taiwan and The natural range of this species is type, to 2m long, rarely to 3m. These south to islands in Indonesia and the Macaronesia and southern Europe. usually bear one to three large, scaly Philippines. One species, W. radicans, It is found abundantly in the Azores, bulbils in the axils of pinnae near the has a disjunct distribution and is Madeira and high rainfall areas of the frond apex. The stipe (frond stalk) is found in Macaronesia and more Canary Islands. It also occurs rarely up to half as long as the leaf blade. rarely in southern Europe. The New in Portugal, Spain, Italy and also on This species is the most frequently World species range from Canada the islands of Corsica, Sicily and encountered in gardens, although it south to Costa Rica. Species in Crete. It has also been recorded from is being usurped by W. fimbriata, and subtropical areas tend to grow in Algeria, apparently as an introduction. has been grown since the late 18th mountainous regions. It demonstrates a relictual distribut- century. Several large gardens in Section Japonicae with two or ion, which means it was once more Cornwall, Ireland and Scotland host three species is rarely cultivated. widespread, and shares close spectacular colonies. Neither bulbils or plantlets occur in ancestry with W. unigemmata. The A few cultivars with atypical this section. split between the two species is fronds, such as ‘Burgessiana’, The third section, Chieniopteris, is estimated to have occurred about 13 ‘Cristata’ (syn. ‘Brownii’) and maintained as a separate genus by million years ago (Li et al. 2014). ‘Plumosum McCormack’, have been Chinese botanists. The two small Woodwardia radicans is very described but have not been seen species are attractive but I am not common in parts of the Canarian recently. The cultivar ‘Crispa’ aware of them being in cultivation. and Madeiran archipelagos. It can actually belongs to W. prolifera. ➤ September 2015 185 genuS profile hardier than W. radicans and are conclusively. I first became aware undamaged at -10°c (H4), and some of this problem after being asked to can survive lower temperatures. identify woodwardias in a Cornish Woodwardia unigemmata has garden during October 2013. become popular and widespread in Despite my initial confidence I cultivation within the last 40 years. found that I was unable to name It is now much more frequently several with any certainty. planted than W. radicans. The Importantly, it should be noted superior hardiness and colourful new that bulbil number is completely growth combine to make this fern an unreliable for identification ideal subject for gardeners who purposes. Both species can produce require a feature plant that is both one to three plantlets in the upper spectacular and easy to maintain. pinnae axils, and occasionally even A bulbil on the underside of a more; up to seven have been Woodwardia radicans frond Differentiating W. radicans reported in W. unigemmata. and W. unigemmata The intensity of red pigmentation Woodwardia unigemmata The differences between W. radicans in the colourful new fronds is very This is similar to the previous species and W. unigemmata are subtle. useful. Woodwardia unigemmata in overall appearance but the fronds Although the extremes can be told usually has bright reddish or orange are relatively narrow with more apart fairly easily, some plants are new growth, whereas colour is widely spaced pinnae. A large colony almost impossible to identify usually lacking or faint in W. radicans. of this magnificent fern can create an awesome spectacle in spring and summer when a mass of intensely coloured young fronds are unfurling. In the best forms they are a bright red but can vary from orange through to burgundy. As the fronds mature they fade to green but new fronds usually emerge throughout the growing season giving a long period of colour. Woodwardia unigemmata occurs naturally over a vast area of east Asia, The first pinna lobe ofWoodwardia unigemmata arises on the side of from India through China to Japan the pinna facing the apex and Taiwan. Fraser-Jenkins (2008) has shown that W. biserrata, a name that could have usurped The colourful new fronds W. unigemmata, is actually based of Woodwardia unigemmata on a wrongly localised specimen of W. fimbriata and can be disregarded. It has been introduced to cultivation many times from different localities, resulting in variation in frond form and colour intensity. Additionally, several different clones with undulate fronds are in cultivation. There is also some variation in cold hardiness. However, most clones seem to be significantly 186 September 2015 PlantsmanThe the pinnae axils of W. radicans and W. unigemmata. Plantlets occur in both species, sometimes completely covering the frond surface. It is now known that W. orientalis is a fertile allotetraploid species derived from a sterile hybrid between diploid W. prolifera and a second, as yet uncertain, species (Takamiya et al. 1992). Most plants in cultivation appear to be W. prolifera. True W. orientalis is possibly grown and I am currently searching fern collections for plants that may be it. Woodwardia prolifera is a large plant that can have fronds more than 2m in length. The young fronds vary in colour, sometimes green but often very intensely coloured carmine or Woodwardia radicans (left) orange, frequently more colourful and W. unigemmata (right) than those of W. unigemmata. When the fronds are covered in tiny However, many plants of W. radicans rather technical distinction, it does plantlets, W. prolifera is easily have some trace of colour, and occas- prove reliable in the majority of distinguishable from W. unigemmata. ionally a pale orange colouration. cases. It is important to check for Even when they have dropped, small Of course, unfurling frond colour presence of a vein in the lobe, as scars remain on the frond surface.