All posts by Tim Pyner

A New Classification of Blechnum

Towards the end of 2016 several papers were published that in my view will have a profound effect on fern classification in general and the Hard Fern family in particular. Firstly the paper published by the Pteridophyte Phylogeny Group (PPG 1, A community-derived classification for extant Lycophytes and Ferns, Journal of Systematics and Evolution 54(6) 563-603) aims to produce a consensus classification for ferns and Lycophytes. 94 pteridologists have contributed to the project and the new classification should hopefully bring stability for some time. There are still genera that require further more detailed research and these are highlighted so this will not be the final word – not that there ever will be. This new classification does not spring any major surprises and in general summarises phylogenetic research over the last 20 years. The one family that does undergo a major re-organisation is the Blechnaceae. This due to the acceptance by the PPG of 2 papers published in late 2016. These are; Gasper et al, Molecular Phylogeny of the fern family Blechnaceae (Polypodiales) with a revised genus level treatment , Cladistics published online 19th October 2016 and Gasper et al, A classification for Blechnaceae (Polypodiales; Polypodiopsida); New genera, resurrected names and combinations, Phytotaxa 275(3) 191-227. The second of these papers publishes several new genera and resurrects some older genera as well as publishing many new species combinations within these genera.
Blechnum has previously been known to be morphologically very diverse and molecular studies have shown that most of the previously accepted genera are nested within Blechnum itself. There are 2 ways to deal with this problem, lumping or splitting. Recently it has been suggested that Blechnum should be enlarged and genera such as Doodia should be included. This option only delays the inevitable consequences that such well defined genera such as Sadleria should also be included in Blechnum. The new proposals split Blechnum into many smaller genera. Most of these are morphologically consistent and can be easily distinguished as groups of related species.

It will take some time for most of these changes to become generally accepted however I have recently noted that Bowdens Hostas have started to use some of the new generic names on their website so I think it is time to start raising awareness of this new classification.

Here is short list of some of the new and resurrected genera and how the names of some well known species will be affected. Note that Doodia, Brainea and Sadleria survive in this new classification. Many other genera and combinations can be found in the paper cited above.

Now a small genus that retains species such as B. occidentale, B. appendiculatum, B. australe and B. hastatum.

Our native Hard Fern (Blechnum spicant) becomes Struthiopteris spicant a name that was well known in the past.

B. penna-marina = Austroblechnum penna-marina. Unfortunately subsp. alpinum has yet to be combined in Austroblechnum but will hopefully be in the near future.
B. blechnoides = Austroblechnum banksii, a welcome return of the well-known specific epithet.
B. colensoi = A. colensoi
B. chambersii = A. lanceolatum
B. mochaenum = A. lechleri

B. cordatum = Parablechnum cordatum
B. novae-zelandiae = P. novae-zelandiae
B. montanum = P. montanum
B. capense = P. capense

B. brasiliense = Neoblechnum brasiliense

B. gibbum = Oceanopteris gibba
B. cartilagineum = O. cartilaginea

B. discolor = Lomaria discolor
B. nudum = L. nuda

B. tabulare = Lomariocycas tabularis
B. magellanicum = L. magellanica
B. cycadifolium = L. cycadifolia
B. palmiforme = L. palmiformis

B. fluviatile = Cranfillia fluviatilis
B. vulcanicum = C. vulcanica
B. longicauda = C. longicauda

B. orientale = Blechnopsis orientalis

Tmesipteris growing on Dicksonia in an English garden

Tmesipteris or Fork Ferns are a small genus of primitive ferns related to the Whisk Ferns, Psilotum. They originate from Australia and islands in the South-west Pacific. Occasionally found on imported trunks of tree ferns, usually Dicksonia antarctica they are rarely seen now as trunks are vigorously cleansed of all epiphytes. I have occasionally noticed Tmesipteris on trunks of tree ferns grown undercover and once on a Dicksonia in a Cornish garden. I have also been notified of plants in an Irish garden but usually they do not seem to persist for long. Therefore it was of some interest that Colin Pope, a volunteer at Ventnor Botanic Garden, Isle of Wight, reported finding several plants growing on Dicksonia in the gardens. Earlier this week Andrew Leonard and I met with Colin on the Isle of Wight and he showed us the colony. The Dicksonias were planted in 2005 in a small gulley. Some were imported from Tasmania and supplemented with smaller plants obtained from Logan Botanic Garden. The Tmesipteris were seen on 4 trunks of the Tasmanian specimens and around 30 ‘fronds’ were present. It is difficult to work out if some of these ‘fronds’ were separate plants or if some were arising from a hidden rhizome. Most of the fronds seemed healthy and the colony seems to be thriving. Colin said that some of the smaller ‘fronds’ appear to be recent so the colony may be increasing in size. 2 fronds bore ‘sporangia’, correctly termed synangia, and I was able to identify them as probable T. obliqua which is endemic to South-east Australia. Microsorum pustulatum and Rumohra adiantiformis were also present on some of the Dicksonias. It is of great interest that this colony has been noticed and can be monitored for signs of decline or increase in the future.

The Cliff Fern family, Woodsiaceae

In recent molecular classifications the family Woodsiaceae has been radically pruned and has lost almost all the genera with which has been associated over recent decades. Familiar genera such as Athyrium, Deparia and Diplazium are now placed in the Athyriaceae. Cystopteris and Gymnocarpium are now included in the Cystopteridaceae and the Onocleaceae includes Matteuccia and Onoclea. Woodsiaceae is now restricted to Woodsia and a handful of closely related segregate genera.
Until a few weeks ago no comprehensive molecular study of the genus had been completed but now 2 unrelated papers have been published. What is more, although the 2 studies have reached similar conclusions their final taxonomies differ substantially.
In the first to be published in June by A. Shmakov, The New System of Woodsiaceae in Turczaninowia (18)2, pp. 11-16 the author concluded that Woodsia should be split into 7 genera. These are (in alphabetical order) Cheilanthopsis, Eriosoriopsis, Hymenocystis, Physematium, Protowoodsia, Woodsia and Woodsiopsis. Under this classification Woodsia alpina, W. ilvensis and W. polystichoides are retained in Woodsia but most of the North American species are included in Woodsiopsis. Woodsia fragilis is the sole member of Hymenocystis.
The second study was published earlier this month by Y. Shao et al. Molecular Phylogeny of the Cliff Ferns (Woodsiaceae: Polypodiales) with a Proposed Infrageneric Classification in the open access journal PLoS ONE 10(9). Although their findings are similar they have concluded that the most practical taxonomic arrangement is to include all the species in Woodsia that is then subdivided into 3 subgenera.
I suspect that the latter classification will be adopted by most pteridologists although further research may prove me wrong.

While researching this post I have noticed that Woodsia fragilis that is occasionally seen in cultivation has an invalid name as it is a later homonym. The correct name is Woodsia caucasica (or Hymenocystis fragilis if you prefer to split).

Here is a magnificent example seen recently in Bridget Laue’s garden.

Woodsia caucasica (Syn. W. fragilis
Woodsia caucasica (Syn. W. fragilis

Ferns in Members Gardens – 2015 update

I have posted my updated list for 2015. As usual a few losses across various groups. Most of the less hardy species came through last winter either undamaged or have recovered. Athyrium rupestre was a disappointing loss but I had already noted that this species was particularly adversely affected by heat and dryness. It would probably be OK in cooler, wetter parts of the country.

I have found that some Polystichum species are rather unreliable. If they do well they can suddenly deteriorate or die the following year. This year I have lost P. setigerum, P. x bicknelii and a P. braunii. P. chilense did very well last year but is now in intensive care as is a 2nd P. braunii. Also P. wawranum is showing worrying signs such as a lack of new fronds. I am not sure why Polystichums seem to be particularly affected by this phenomenon.

Each year I only list ferns that are planted in the garden or grown in planters or containers that have survived at least 1 year exposed to the elements. There are several new plants on the list that have come through last winter in the garden. One new addition to the list although it has been grown in a sink outside for over 20 years is Asplenium ritoense. This occurred as a contaminant in a spore sowing of A. oblongifolium and I have not been able to identify it to my satisfaction until recently. It is an attractive, clumping species and has proved to be very hardy but I have never seen it anywhere else. It would be of interest if anybody else grows it. Presumably the original spore came from a horticultural source as the 2 species have different natural ranges.

Asplenium ritoense.
Asplenium ritoense

Just one taxonomic update. I have followed Labiak et al. in American Journal of Botany 101 ( 7 ): 1207 – 1228 , 2014 and have renamed Lastreopsis glabella and L. microsora as Parapolystichum glabellum and P. microsorum respectively.

In my previous list I also noted that there was a question mark regarding which species in the Adiantum venustum group was actually in cultivation. I have now looked into this and I happy to report that most or all cultivated plants are indeed A. venustum. 2 others species could possibly be in cultivation, A. tibeticum and A. fimbriatum, however they must be very rare. Adiantum davidii has been misidentified as A. fimbriatum in the past.

Asplenium x tagananaense – still hanging in there!

Asplenium x tagananaense, the hybrid between A. hemionitis and A. onopteris must rank as one of the rarest ferns in the world. A single plant was discovered in 2009 on the island of Tenerife. Despite careful searching only this one plant has been found. While on Tenerife earlier this month I went to see if I could refind it. It is located on a ferny trail near to the village of Taganana after which it is named.

I managed to relocate the fern and although smaller with fewer fronds than on my previous visit in 2009 it appears to be in good health with a new frond emerging.

The two parents are very unlike in frond structure. A. x tagananaense resembles A. hemionitis more closely than its other parent but the lobes themselves are pinnately lobed. I examined the fronds carefully to see if I could recognise any other characters that may indicate its hybrid nature. One small character was fairly obvious – tiny teeth on the cartilaginous margins of the frond. I examined many fronds of A. hemionitis and the margins were smooth or occasionally a few small blunt teeth were found. In the hybrid the teeth were small, but pointed and occurred all round the frond. A. onopteris has an almost undetectable margin without teeth. Mentioned but not emphasized in the original description, this may prove to be a useful diagnostic character although unless other plants are found it is impossible to know how consistent the teeth character is.

It does seem certain that this plant will probably expire in the next few years so if you are in an area where both species occur keep a look out for any odd forms- you never know it may turn out to be the second example of this interesting hybrid.

aAsplenium x tagananaense  - reduced
The sole plant with 2 mature fronds and a new crozier. Note adjacent plant of A. onopteris

aAsplenium x tagananaense frond reduced
Frond upper surface

aAsplenium x tagananaense underfrond reduced
Frond lower surface

aAsplenium x tagananaense teeth reduced
Small teeth on frond margin

Plagiogyria – a fascinating oddity

Plagiogyria is the sole genus in the family Plagiogyriaceae. There are about 13 species currently accepted, 10 in East Asia and the western Pacific and 3 in the New World from Mexico and the Greater Antilles south to continental South America. In appearance they are remarkably similar to species of Blechnum, those with dimorphic fronds in particular. However the resemblance is entirely superficial. During the 19th century they were usually classified under Lomaria along with dimorphic Blechnum species. In the early 20th century it was realised that they were unrelated to Blechnum and were placed in their own family that was thought to be related to Osmundaceae or Cyatheaceae. The sporangia closely resemble those of tree ferns and recent molecular evidence indicates that they are indeed closely related to some of the smaller families in the Cyatheales.

Despite their remote relationship the morphological differences from Blechnum are quite subtle. The most easily examined external difference can be seen in the scales. In Blechnum these are always apparent on the rhizomes and young fronds and they often persist on the mature fronds even if only sparsely. In Plagiogyria scales are completely absent. This is most obvious at the rhizome apex were the naked unfurling fronds can be observed.

Plagiogyria are almost unknown in cultivation in the UK. I am not sure why this should be so as they are very attractive ferns. I am aware of 4 species that are currently grown or have been recently in cultivation.
Plagiogyria pycnophylla, a robust species with handsome glossy fronds.
P. stenoptera, smaller, shortened pinnae lobes along stipe.
P. matsumureana, deciduous so should be the hardiest species. This used to grow by the old alpine house at RBG Kew. I wonder what happened to it?
P. glauca. I have not seen this but there are pictures on the internet of a plant in cultivation. The frond lower surfaces are glaucous or even an amazing bright white.

In Japan I saw 3 more species, P. japonica, P. euphlebia and P. adnata along with probable hybrids. They did not grow in unusual habitats and appeared to require typical woodland fern growing conditions, adequate moisture, humidity, shade and good drainage. There does not appear to be any reason why these ferns are so scarce in British gardens unless they are difficult from spores.

I would be very interested to hear from anyone who is growing these interesting ferns.

Plagiogyria pycnophylla, reduced
Plagiogyria pycnophylla

Plagiogyria euphlebia Japan reduced
Plagiogyria euphlebia

More on Woodwardia orientalis

I may have been too hasty in assuming true Woodwardia orientalis was not in cultivation! Reviewing my Woodwardia photos I came across this photo taken in Glasgow Botanic Gardens Kibble Palace earlier this year. Comparing it with my photos taken Japan I think this is possibly it. I will still need to measure spores and stomatal guard cells to confirm but it does look right.

W. orientalis possible, Glasgow BG  reduced.
Possible Woodwardia orientalis– Glasgow Botanic Garden August 2014

Here is probable Woodwardia prolifera growing outside in a Dutch garden showing the narrower, caudate pinnae lobes.

W. prolifera A. de Pena garden, Holland reduced.
Probable Woodwardia prolifera, Netherlands August 2014

Woodwardia orientalis and W. prolifera update

Further to my previous post I have now measured spores and stomata guard cells of both species. Usually tetraploids will have larger spores and guard cells than diploids and this has proved the case here. Despite the small sample i.e. 1 plant of each species, the differences are so marked that I am confident that a wider sample will give similiar results. The increase in size for spore measurements was around 15% and for guard cell length about 20% for the tetraploid W. orientalis.
W. prolifera
Spore length = 75-78 microns
Guard Cell length = 37-40 microns

W. orientalis
Spore length = 88-90 microns
Guard Cell length = 50-55 microns

The 2 species can be difficult to separate when young or poorly grown. However, the differences in these measurements are such that small or non-fertile plants of either species should be reliably identified.

I will now be checking possible candidates for true W. orientalis whenever I encounter them.

Update December 2014. I have recently measured guard cells from some different plants of W. prolifera and the sizes are more varied ranging from 35-51 microns. As it stands there is an difference in mean length but I will need more measurements of W. orientalis to confirm my earlier confidence that these will prove to be a reliable character. Current measurements indicate a mean lengths of below 50 microns for W. prolifera and exceeding 50 microns for W. orientalis.
Further spore measurements for W. prolifera also show increased variation ranging from 65-80 microns, still substantially smaller than in the tetraploid species.

Woodwardia orientalis in cultivation

The fern known as Woodwardia orientalis in cultivation actually comprises two closely related species. True Woodwardia orientalis is an allotetraploid species derived from a hybrid between W. prolifera and an unknown second parent. Woodwardia prolifera is a diploid species that has been known under the names W. orientalis var. prolifera or var. formosana. The latter name is frequently used for cultivated plants.
Horticultural literature usually separates Woodwardia orientalis and its varieties from other Woodwardia species by the characteristic plantlets or propagules scattered over the upper surface of the frond. Other bulbiferous species have larger plantlets restricted to the upper rachis. The var. formosana is often characterised by having many more bulbils than the nominate variety, however this is not correct.
During my ongoing research into Woodwardia in cultivation I have been trying to work out if one or both species are grown. I have also been puzzled about the actual differences between the 2 species. Herbarium specimens often comprise small fronds or frond portions and although the 2 species appear to be morphologically distinct when mature, small fronds are alarmingly similiar.
My participation in the recent BPS trip to Japan gave me the opportunity to examine mature specimens.

I saw Woodwardia orientalis growing in a couple of natural sites. Mature fronds are relatively small, mostly less than 1 metre in length. The pinnae lobes are rather broad and abruptly tapered. One or 2 basal basiscopic pinnae lobes are absent.

Woodwardia orientalis plant reduced
Woodwardia orientalis growing wild in Japan

Woodwardia orientalis frond reduced
Woodwardia orientalis-frond showing pinnae and lobes.

I only saw Woodwardia prolifera in Kyoto Botanic Garden. It is a much larger plant with fronds 1.5 – 2 metres in length. The pinnae lobes are narrow, acuminate or caudate and 2 or 3 basal basiscopic pinnae lobes are absent.

Woodwardia prolifera plant reduced
Woodwardia prolifera. Large plant growing in Kyoto Botanic Garden

Woodwardia prolifera frond reduced
Woodwardia prolifera – frond showing pinnae and lobes

Both species had small plantlets on their fronds although most had fallen when observed (late October, early November).

Despite their variability I now believe that most or all plants in cultivation in the UK (also Netherlands and Belgium), judged on their overall morphology, are W. prolifera. I will be investigating ways to identify the 2 species more reliably. Spore size may be one method to tell the species apart but information is currently lacking. It is quite possible that true W. orientalis is lurking in some collections. I would be very interested if anyone believes they may have the true species in cultivation.

Blechnum chilense or cordatum. Which is correct?

Horticulturalists and botanists have for some time had conflicting views in regard to the correct name of this commonly cultivated species of Blechnum originating from temperate South America. Botanists call the plant Blechnum cordatum while gardeners insist that the correct name is Blechnum chilense and that B. cordatum is a different, tropical species differing in many ways from the cold-hardy cultivated plants. It is a member of a difficult group that botanists treat in a variety of ways, mostly as a single variable species.

Part of the confusion results from the ambiguous collection details recorded on the type specimen of Lomaria cordata (= B. cordatum). This specimen resembles the plants cultivated as Blechnum chilense. The type locality is given as Perou-Concepcion. However the collector, Joseph Dombey, did not visit this area but did travel from Peru to Concepcion in Chile where he apparently collected the type specimen.

As the type of Lomaria cordata (published 1811) was collected in Chile, where it is the only member of the complex, the correct name under the rules of priority is Blechnum cordatum. The basionym of B. chilense, Lomaria chilensis, was not published until 1824.

I am sure that the complex includes more than a single species, however we will have to wait until detailed molecular, cytological and morphological studies have been carried out before a more complete understanding is achieved.

Meanwhile, irksome as it is to gardeners, it does appear that botanists are correct on this occasion and the name that should be used is Blechnum cordatum.

1. Blechnum cordatum, Cornwall 2013
Usual form found in UK gardens
2. Blechnum cordatum, Belgium 2014
Different form with less undulate pinnae seen in Belgium