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.  

Polypogon arrives in Aberystwyth

Polypogon viridis has arrived in Aberystwyth. An established colony (c. 50 plants) is growing on a paved area adjacent to the Alexandra Road / Rheidol Retail Park roundabout (SN58608167). Given the size of the colony I presume that it actually arrived last year so may already have been noted by other recorders. It also occurs at the University's Fron Goch farm where it currently grows only inside one of the abandoned glasshouses (SN60618259).

Picnic Island

Yesterday evening I visited a place called Picnic Island. A small rocky promontory cut off by the railway on the north bank of the Dyfi Estuary overlooking Ynys-las. Half an hour poking around revealed some nice species in the unpromising looking mown picnic area including Trifolium striatum, T. micranthum, Koeleria macrantha, Sagina apetela, Aira caryophyllea and Aphanes arvensis.

Trifolium striatum,
SN626962, VC48

Trampled ground by the path to Penhelig revealed a single plant of Catapodium marinum, lots of Trifolium arvense and Origanum vulgare. Just above high water in an overhang of the cliff two plants of Asplenium obovatum were flourishing.   

Asplenium obovatum & Umbilicus rupestris,
SN626962, VC48

Off now to the National Botanic Garden of Wales to prepare for tomorrow's BSBI meeting.

Circaea alpina

Yesterday evening I took a trip up the Llyfnant Valley to a gorge on the Ceredigion Montgomeryshire border where Circaea alpina can be found. Recent (post 2000) Welsh records of this rare species are from the Llyfnant site and, according to BSBI Maps, Caernarfonshire and Brecknockshire (though recent records are not listed in the county rare plant register). Two historic sites for the species in Merionethshire haven't been updated for some time and there are a number of  (doubtful?) records for Montgomeryshire on NBN Gateway but not BSBI Maps.  

Circaea alpina,
Llyfnant Valley, SN7596, VC46

Having seen the plant in situ (though not yet in flower) I carried on to Corris; one of the historic Merioneth sites. No luck here but I was running out of light and didn't cover much of the site so there's still potential.

Survey & Oxalis

Recently I spent a week pootling around the Aberystwyth district trialling my new protected environment weed survey and collecting samples of Oxalis section Corniculatae and Cardamine of the flexuosa group. After a number of false starts I'm now fairly happy with the survey protocol. It has become much more complex but it should allow me to:

• Define the weed community of the protected environment
• Relate the internal community to that of adjacent external communities   
• Differentiate niche communities such as pots and cracks 
• Describe the seasonal variation within these communities

My living collection of Oxalis and Cardamine is growing and I should soon have enough to begin my screening using molecular markers and cytological techniques. With any luck this will allow me to better define taxonomic units and slot them in to global studies and work being conducted by other botanists. Before all of this I thought I'd post a few of the most recognisable Oxalis taxa.   

Firstly the deep purple Oxalis corniculata var. atropurpurea. This taxon is normally very distinctive due to its colouration though there seems to be some variation partly due to moisture and light.

Oxalis corniculata var. atropurpurea,
abandoned glasshouse,
 Fron Goch University Farm,
SN 60602 82591, VC46

Second the smallest species: O. exilis. Less variable than other taxa, normally the most prostrate and often growing in tight mats its leaves are always a fresh bright green and its flowers are borne singly.

Oxalis exilis, abandoned glasshouse,
Fron Goch University Farm,
SN 60602 82591, VC46

Oxalis exilis, abandoned glasshouse,
Fron Goch University Farm,
SN 60602 82591, VC46

Lastly possible Oxalis dillenii a much scarcer species. It was abundant in a single abandoned glasshouse at Llanbadarn. Obviously larger, more upright, its flowers are produced in small corymbs and its leaves have a slightly bluish tinge.

Oxalis dillenii?, abandoned glasshouse,
 Llanbadarn Campus, SN 60607 81092, VC46

Oxalis dillenii?, abandoned glasshouse,
 Llanbadarn Campus, SN 60607 81092, VC46

Hopefully I'll have more detailed information as my research progresses over the next few months. 

Urtica membranacea

The seasonal visit to EGG, this year in Liverpool, was appended with a short stopover at Ness Botanic Gardens. The purpose of this visit being the collection of Oxalis and Cardamine plants to form the basis of my initial taxonomic study. Our tour of Ness' glasshouses and polytunnels was assisted by Tim Baxter, the garden's botanist. In the last polytunnel of our tour my supervisor John Warren spotted a strange nettle growing in a number of the large planters; a nettle with a crucifix of short purple racemes of male flowers atop a small, annual and almost stingless plant. After some fruitless discussion as to its identity, I bagged two of the four plants for later determination. Flora Europea revealed the plants to be Urtica membranacea, previously known as U. dubia. The first UK record of this southern European species was made in Warwick in 2006 and there have been a scattering of other records across the UK in the intervening years. The species has previously been recorded in Pensby about five miles further along the Wirral.

Urtica membranacea, Ness Botanic Gardens,
VC58, SJ 29727 77557, 01/04/15

Urtica membranacea, Ness Botanic Gardens,
VC58, SJ 29727 77557, 01/04/15

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