Glasshouse Aliens

I've been sorting through my specimens from my early summer survey of botanical garden glasshouses. Among the many unidentifiable seedlings there have been a few species of interest that I have managed to identify. There is a particular satisfaction using a range of piecemeal sources to determine the identity of a plant not included in Stace though it is often impossible to be certain of a determination at the species level of a plant that could have originated anywhere in the world. Below are a selection of taxa that I have at least determined to genus.

Firstly an easy determination, Solanum chenopodioides, which I found growing in a disused propagation glasshouse at RHS Wisely. The vernacular name for this species is Tall Nightshade and it was large forming a messy bush with tough, woody stems. A dense covering of retrose hairs all over is another character of this species. Originating in South America this species is a very local casual in the UK.              

Solanum chenopodioides, Fruits,
RHS Wisely, TQ 06498 57977, April 2013

Parietaria officinalis grew in abundance in many of the Edinburgh glasshouses. This larger relative of the common P. judaica has longer leaves and also differers in characters of the flower and fruit. Very locally naturalised in the UK this species originates from eastern Europe.   

Parietaria officinalis, Edinburgh Botanic Gardens, May 2013

Growing amongst moss intended for orchids and cycads was a small glandular plant with a pocket shaped yellow flower. Research revealed it to be Calceolaria tripartita a South American weed of damp mossy habitats. This species is not listed in Stace but is mentioned in Clement & Foster's 'Alien Plants of the British Isles' as having occurred in the UK a couple of times.    

Calceolaria tripartita,
Edinburgh Botanic Gardens, May 2013

A frequent weed in the public glasshouses at Edinburgh was Fuchsia procumbens. Very different to the large Fuchsia magellanica familiar from hedges and gardens this species revealed itself as a Fuchsia by way of its succulent, barrel-shaped fruits quite similar to those of the familiar species.  

Fuchsia procumbens,  Edinburgh Botanic Gardens, May 2013

In a wet patch at the edge of the Eden Mediterranean Biome there was plentiful Polypogon viridis. I have only recently become acquainted with this grass which, according to the floras, is very similar to Agrostis stolonifera but looks subtly different in practice. I found it growing near Holyhead Port (VC52) and it has recently colonised Bangor (VC49) where it is now abundant along the edges of some streets.

N.B. I've just found this at the NBGW growing beside a track and also in a disused glasshouse. I've taken the opportunity to compare it with Agrostis stolonifera under the microscope. The key difference is in the comparative lengths of the lemma and the paella, equal in P. viridis and with the paella shorter in A. stolonifera. The glumes of P. viridis are hispid all over while those of A. stolonifera just have a few relatively large bristles toward the end of the keel. The pedicels of P. viridis are also hispid while those of A. stolonifera are smooth. John Poland's vegetative key notes the ciliolate margin to the end of the ligule and this shows up nicely on the P. viridis while the ligule of A. stolonifera is smooth. These notes are based on a couple of plants from one population so may not apply to all plants particularly given the variability of A. stolonifera. Now to find the hybrid...

Polypogon viridis,
Med Biome, Eden Project, April 2013

As mentioned in a previous post the flora of the Tropical Biome at Eden was rather confusing. One relatively easy species to determine was Digitaria ciliaris. This, the most tropical of the three Digitaria species naturalised in the UK, is distinguished on characters of the glume and lemma.

Digitaria ciliaris,
Tropical Biome, Eden Project, April 2013

A final plant also from the Tropical Biome at Eden, this time one that has eluded final determination. Clearly a member of the Urticaceae it was also present in the tropical house at RHS Wisely. My best guess as to its identity is the genus Boehmeria but trawling the internet has failed to help choose from the 100 or so species within this genus. So, if you happen to know its identity please do comment.

N.b.- Having DNA barcoded my specimen of this plant I can now say I was barking up the wrong tree looking in the Urticaceae as it came back as a species of Acalypha in the Euphorbiaceae. This large pan-tropical genus derives its name from the Greek word for nettle (akalephes) in reference to its often nettle like leaves making my previous misidentification a little less embarrassing.

Acalypha sp.,
Tropical Biome, Eden Project, April 2013

Eden Project

I recently returned from the second stage of botanical garden tour. The garden I visited is one unlike any other, The Eden Project. More a grand socio-architectural statement than a collection of plants Eden is without doubt very impressive even if the plants don't always take centre stage.

The Mediterranean Biome at Eden, April 2013 

From the lip of a disused china clay pit a steep track makes a zigzag descent to Eden. At the top of the slope I was distracted from my introductory wander by a stand of large rugose-leafed plants. These were Balm-leaved Figwort, Scrophularia scorodonia. This species has a very limited distribution in the UK, being confined to the south-west and I can not recollect having encountered it previously. However since my return I happened upon this species in my home town of Aberystwyth where it has escaped from the garden of the late Ceredigion botanist J. H. Salter (Chater, 2010).

Scrophularia scorodonia,
Eden Project, April 2013

Following my informative tour (with Tim Pettitt) I began surveying in the Mediterranean Biome. A couple of hours of crawling through the prickly arid scrub yielded a number of surprised looks and a wide range of weed species. These included the ubiquitous, the unidentified and the probable intentional introductions. One species in this latter category was Tall Rocket, Sisymbrium altissimum. A frequent weed in most of urban Britain it still presented a slight puzzle for a occidental botanist such as myself.        

Sisymbrium altissimum, Mediterranean Biome,
Eden Project, April 2013

Moving then to the Tropical Biome, a confusing situation for any attempt at the eternally complex question of defining 'what is a weed'. Many ground cover species had clearly been introduced for the express purpose of going 'wild' so, while they were self propagating, this was their intended purpose and, therefore, not a 'weedy' characteristic. Anyway, the most virulent coloniser was a species of a family with which I was not previously familiar; the Acanthaceae. This tropical family is well represented in UK tropical houses and seems very geared toward vegetative colonisation. The identity suggested for this by someone (I can't remember or find his name) at Eden was a species of the genus Nelsonia.              

Probable Nelsonia sp., 
Tropical Biome, Eden Project, 
April 2013

The Tropical Biome was also full of insect life. Particularly noticeable was the White-footed Ant, Technomyrmex albipes. This tropical tramp species, originally from the Indo-Australian region, has recently colonised western glasshouses and has rapidly become a significant pest at the expense of other tropical ant species. In at least one case it was purposely introduced to control another ant species. At this task it  excelled, but, as evidenced by many such examples, the biological control agent replaced  the problem rather than eradicating the problem (Boer, et al., 2008).  

Probable Technomyrmex albipes on a Strelitzia flower ,

Tropical Biome , Eden Project, April 2013

Leaving the Biomes I noticed a tiny red splash of colour among the gravel. This was the Mossy Stonecrop, Crassula tillaea. This species has a rather scattered distribution and seems to be spreading. Of the three records for North Wales shown on the BSBI map I know two of the sites are car parks at popular tourist destinations. I presume that it is being spread on car tires from one car park to the next on the wheels of unsuspecting holidaymakers.     

Crassula tillaea, Eden Project, April 2013

Wandering out through a wooded area I came across a planted glade of primroses and cowslips as well as two plants of their hybrid Primula x polyantha. This hybrid is frequent almost whenever the parents meet and probably arose in situ. This is also the parentage of a number of the showy horticultural Primula varieties.

Primula x polyantha,
Eden Project, April 2013

Boer, Peter, and Bert Vierbergen. "Exotic ants in the Netherlands (Hymenoptera: Formicidae)." Entomologische Berichten 68.2 (2008): 29.
Chater, A.O., 2010, Flora of Cardiganshire. Self published, Aberystwyth.