Monday, 30 September 2013

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


  1. We've found Polypogon viridis in Leicester suburbs and Oli P's sacrevert Blog has reports of it in Derbyshire and South Yorkshire. Louise

  2. yes, seems to be increasing all over, just found it at the National Botanic Gardens of Wales

  3. Try Acalypha siamensis, have seen it in a few glasshouses.