Tropical Glasshouse Weeds

A quick look around the propagation glasshouses at the National Botanic Gardens of Wales today turned up two weeds of tropical glasshouses that I haven't previously recorded anywhere in Wales. 

Psilotum nudum  and Pilea microphylla are restricted to glasshouses in the UK and have both been covered in my previous post on Ireland. 

The tropical house and its associated propagation space are both relatively new having been opened in 2007. It may be that associated weeds have taken a while to arrive from various sources but a large influx of material from the Chelsea Flower Show last year may also be responsible for importing both species.  

X Agropogon robinsonii & others, National Botanic Garden of Wales

A visit to the gardens during last week's heatwave roved productive with a couple of cudweeds, a spurge and a intergeneric grass hybrid.

Polypogon viridis is now among the most common grasses around the propagation glasshouses at the gardens. Reasoning that this increased my chances, I set to hunting for its intergeneric hybrid with Agrostis stolonifera: X Agropogon robinsonii. Despite somewhat conflicting literature including what appears to be an erroneous description in Sell & Murrell I managed to find a single putative hybrid plant. Examination back home under the microscope showed a mixture of characters of the two parent species and intermediate character states. The anther length (c. 1.1mm) being closer to A. stolonifera and much longer than that of P. viridis (c. 0.6mm). The lemma and palea resembling those of P. viridis both in shape and relative length (almost equal). The glumes having sparse scrabidity from P. viridis but more pronounced bristles on the keel from A. stolonifera. The end of the ligule  being ciliolate as in P. viridis but the overall structure of the tiller more like that of A. stolonifera. Given these features I'm happy to call the plant X Agropogon robinsonii though it will probably need to be sent off for confirmation. As far as I can tell this hybrid has previously only been recorded four times in the UK (all but one in the Channel Islands) and once in France. Given the rapid spread of P. viridis in recent years it may be that other people have found this hybrid recently. If not it is probably worth keeping an eye out for wherever P. viridis occurs.

***Note***  Now 'cautiously confirmed' by Tom Cope at Kew as the fifth ever record of this taxon. The 'cautious' prefix having to do with some previously confirmed material of this this taxon having been redetermined as pure Polypogon and the fact that the only other available material (a Guernsey collection from 1997 by Rachel Rabey) is much larger and more distinctly intermediate between the parent taxa than NBGW material. On balance however the male sterility and persistent glumes were, according to Tom Cope, enough for the 'cautious confirmation'. Confirmation is with thanks to Richard Pryce, Arthur Copping, Tom Cope and Rachel Rabey.      

X Agropogon robinsonii, culm,
NBGW, SN 52105 18410

X Agropogon robinsonii, habit,
NBGW, SN 52105 18410

X Agropogon robinsonii, tiller,
NBGW, SN 52105 18410

X Agropogon robinsonii, inflorescence,
NBGW, SN 52105 18410

Now cudweeds, the most interesting of which was a single plant of Gnaphalium luteoalbum growing on gravel between two propagation glasshouses. This species is restricted as a native to a few sites in the south of England and occurs as a scattered casual elsewhere but appears not to have been recorded in Wales post 1930. Despite fairly extensive searching I could not locate any more plants suggesting that this species may have only just arrived at the gardens.

A more frequent cudweed: Filago vulgaris was abundant on on parched ground around the science block. Bringing the cudweed total for my trip to three including the common Gnaphalium uliginosum.

Gnaphalium luteoalbum,
NBGW, SN 52138 18412

Filago vulgaris,
NBGW, SN 51970 18239

Finally a spurge: Euphorbia stricta is very local as a native being restricted to the open ground in woodlands around the southern Welsh borders. At the gardens it grows in abundance behind a single polytunnel. I don't know if it arrived at the site of its own accord as a casual or, more likely, either as a horticultural species or as part of the Garden's Welsh Rare Plants Project.

Euphorbia stricta,
NBGW, SN 52053 18410

Greater spotted woodpecker, dead from flying into glasshouse,
and a calliphorid fly, NBGW

National Botanic Gardens Autumn '13

I've been based at The NBGW for the last month as my MPhil deadline is fast approaching and it helps to be far from the myriad lights of Aberystywth. Most of my time has been spent in front of a computer or with a pipette in hand desperately making up for lost time. However I have been out into the world as the old farm house that serves as accommodation for myself and a few other students is a short walk across the gardens and through some damp cattle fields. On these twice-daily trips I've noticed a few plants beyond those planted by horticulture.

The first of these grows in the slate beds where the path enters the gardens. Veronica peregrina is a small speedwell introduced from North America. Its tiny whitish flowers subtended by long bracts don't leap out but once I'd noticed it I found it to be abundant in a small area but absent elsewhere, perhaps suggesting it to be a recent arrival. The picture below shows a particularly large individual the majority being so small as to remind one of Montia fontana at first glance. It is scattered about the UK with a few centres of abundance (or recoding awareness) including Liverpool and Northern Ireland and is mostly associated with gardens. Only one previous record exists from Carmarthenshire.       

Veronica peregrina,
Slate Beds, NBGW, Sept 2013

Between the gardens and the fields is a long artificial lake with Little Grebes and Teal feeding among a sea of duckweed. One morning I finally got round to fishing out a handful and found three species to be present. Spirodela polyrhiza made up the vast majority but a few fronds of Lemna minor and Lemna trisulca were also present. Lemna minor is, of course, abundant throughout the British Isles but the other two are relatively uncommon in the west of Wales. 

Spirodela polyrhiza, Habit,
Lake, NBGW, Sept 2013

I've been trying to pay more attention to duckweeds as there are a number of species of interest and they often don't get much of a look in. One introduced species, Lemna turionifera, was added to the British list in 2007 in this paper by Richard Lansdown and has since been found in a few places scattered across the south of Britain. Another species, Landoltia punctata, is also mentioned by Lansdown as having been found in aquatic nurseries in the UK but is not yet known from the wild. This very impressive duckweed website has a lot of information on these species and others as well as useful pictures, keys and introductory duckweed material.  

Spirodela polyrhiza, Underside of frond, Lake, NBGW, Sept 2013

Fringing the lake are tall herbs and bulrush. Almost certainly planted but rather pretty none the less is Typha angustifolia. The smaller and thinner of the two British bulrushes this species is uncommon and mostly introduced in the west. It hybridises with the commoner T. latifolia though I could find no evidence of this having happened at the Gardens despite both species growing adjacent.

Typha angustifolia, Lake, NBGW, Sept 2013

Aberystwyth Glasshouses & The NBGW

I am currently at Aberystwyth University studying for an KESS MPhil in the population dynamics of glasshouse weeds. I'm a couple of months in and I've just progressed from many weeks spent wading through the literature and onto my first visits to actual glasshouses. In an effort to develop a survey protocol I have visited many of the glasshouses in and around Aberystwyth over the last few days. I also made my first visit (in many years) to my KESS partner organisation, The National Botanic Garden of Wales. 

My literature review on the subject of glasshouse weed assemblages turned up surprisingly little information. I found only a single paper describing the floral assemblages in any detail. This solitary paper details the glasshouse weeds of a Polish Botanical garden. Considering the huge diversity of structure and function within the protected environment (greenhouses, polytunnels, etc.)  as well as its economic importance I find it puzzling that no further research exists in this subject area. This lack of previous information makes a wide-ranging survey the only logical first step in my research. 

So the results of my initial, very limited and provisional, survey of thirty-four Aberystwyth glasshouses turned up around eighty species.The season limited both what was visible and what could be identified so the actual number of species in the surveyed glasshouses is certainly greater than my current enumeration. The most frequent species  (listed below) were unsurprising. Some of the frequent but not universal species were less expected. For example Geranium lucidum, a species that occurred frequently both in the Aberystwyth and NBGW glasshouses but one I would not immediately have associated with the habitat.     

Species occurring in 10 or more of the 34 Aberystwyth glasshouses surveyed (listed in order of frequency of occurrence).

1. Epilobium sp.
2. Oxalis corniculata
3. Cardamine hirsuta
4. Poa annua
5. Euphorbia peplus
6. Stelaria media
7. Senecio vulgaris
8. Taraxacum officinale agg.

Some of the more interesting weeds were those that had simply spread from one side of the glasshouse to the other. A particular feature of the varied glasshouses in the University Botanic Gardens at Penglais was the frequency of regenerating pteridophytes. Three species that seemed particularly successful were Phlebodium aureum, Cyrtomium falcatum and Pteris cretica. These species were not only common in the heated glasshouse where they had originally been planted but had also spread to adjacent unheated glasshouses with some success.         

Phlebodium aureum
Penglais Botanic Gardens,
Aberystwyth University, Cardiganshire
(SN 59619 82076) 28/11/12 

Pteris cretica
Penglais Botanic Gardens, 
Aberystwyth University, Cardiganshire 
(SN 59619 82076) 28/11/12 

Further interest was provided by the infallible glamour of carnivorous plants. In the most tucked away glasshouse of the already rather tucked away University Botanic Gardens there is a rather impressive collection of pitcher-plants, sundews, venus fly-traps and bladderworts. Not being an expert on any plant not native to the British Isles I relied on the labels for any indication as to the identity of the plants. In truth it mattered little as the appeal of these plants is universal and even for a cataloguer such as myself it was easy to appreciate their exquisite adaptations without needing to know their identities.       

Sarracenia leucophylla
Penglais Botanic Gardens, 
Aberystwyth University, Cardiganshire 
(SN 59676 82089) 28/11/12 

A somewhat odd highlight of my visit to the NBGW was seeing two of Snowdonia's most enigmatic alpine plants. Admitted both were in pots, a fact that somewhat detracted from the excitement. 

The first of these is a plant that I am now quite familiar with in its Irish settings but one that has a quite mysterious history in Wales. Saxifraga roseacea subspecies roseacea, the Irish Saxifrage was, according to the Welsh Red Data List, last seen in Snowdonia in 1970 (1). I am not sure of the details of the 1970 record but the material in cultivation at the gardens and elsewhere stems from a collection made by the legendary North Wales botanist Dick Roberts. The information I can find suggests that the collection was made in  1962 and was of a single unattached sprig from Cwm Idwal (2). The staff and students at the NBGW are currently conducting genetic studies on  Welsh and Irish material to determine the if there is any difference between the accessions. I have  carefully checked any Saxifraga hypnoides type plants I have encountered in the mountains of North Wales but have, as yet, not managed to rediscover this most enigmatic of Welsh alpines. Below are two pictures of Irish S. roseacea subsp. roseacea each looking very different and each growing in very different situations. The first in steep Philonotis flushes in a shaded corrie on the east flank of Mount Brandon in Co. Kerry and the second on exposed dry limestone pavement on Inisheer, the smallest of the Aran Islands. This page from the BSBI plant crib contains helpful leaf outlines of this group of species. Also, from the Herbaria@home page, here is a nice specimen from 1918 apparently collected somewhere on Snowdon.

Saxifraga roseacea subsp. roseacea
Mount Brandon, Co. Kerry (Q 46282 12593) 25/08/12

Saxifraga roseacea subsp. roseacea 
Inisheer, Co. Glaway (L 99027 01612) 01/08/11

The second plant is probably one of the rarest species in the world if species is the correct term for this apomitic taxon. Hieracium snowdoniense, as detailed in this paper, is a Welsh endemic of which only one  individual is currently known in the wild. It was previously recorded slightly more widely across the three main massifs of Snowdonia but was long thought extinct until the rediscovery in 2002. Seed was collected by Tim Rich in 2002 from the single wild plant and it is from this collection that the plant below derives. Had I come across this plant in the wild I would not have been able to put a name to it with any certainty but the specimen below is helpfully labelled and barcoded.        

Hieracium snowdoniense
NBGW from material collected in Cwm Idwal, Caernarfonshire

KESS is part-funded by the European Social Fund (ESF) through the European Union's Convergence Programme (West Wales and the Valleys) administered by the Welsh Government.