Thursday, 21 September 2017

Loddon pondweed... IN THE THAMES!

I do not use capital letters lightly: the rediscovery of Potamogeton nodosus, the so-called Loddon pondweed, in the River Thames is really very big botanical news indeed! Otherwise known only from the River Loddon, the Bristol Avon and the Dorset Stour, this very rare pondweed was thought to have gone extinct in the Thames in the 1950s and there have been no Oxfordshire records for over 75 years. It was found by Frank Hunt back in August, near Marsh Lock, just south of Henley (SU774815), growing in a part of the river sheltered from boat traffic by a footbridge. Marsh Lock is less than 1km downstream from where it was seen by J.E. Lousley in 1941 and about 5km below where the Loddon joins the Thames. Frank also tells me that there is a patch in the the Berkshire part of the river too.

This is such a distinctive species that the referee for pondweeds, Dr Chris Preston, was quite happy to verify the record from the photograph shown right (and attributable to Frank).

Sunday, 17 September 2017

Stadhampton Square Bash

Puccinellia distans along the A329
Last Sunday was another square bash, when we moved on to Stadhampton (SU69E) from our previous visit to Little Milton (SP60A). Sorry it has taken me so long to write the meeting up! Let's see if I can make it a short one for a change.

As last time we started off with coffee and cake — may this become an established tradition, especially as the weather begins to turn cooler! Many thanks to Fay Banks and her granddaughter for baking delicious brownies for the four of us. After this pleasant diversion from the task of the day we headed out recording. When botanising any village a priority will always be the churchyard and this is where we went first. It was the usual disappointment, ruthlessly mown, but sported Galium verum (lady's bedstraw), Pimpinella saxifraga (burnet saxifrage) and Plantago media (hoary plantain),  a typical assemblage of hangers-on in over-managed churchyards. We did find Epilobium x limosum in a weedy patch, the hybrid between the broad-leaved and hoary willowherbs — no surprises to learn on getting home that this hasn't been much recorded in the county.

Two buckler ferns: the broad Dryopteris dilatata (left) and the narrow D. carthusiana (right). The latter used to be called D. spinulosa on account of the long drawn-out points to the pinnule lobes, and it lacks the distinctive black-marked rachis scales and convex shape of the pinnules seen in D. dilatata.
Stadhampton pond infested with Myriophyllum auqaticum
Square bashing is mostly about gathering as many records as possible from a square, and in settled places this usually consists of alien species, but one seldom fails to find something of interest. Along the A329, for instance, we had a couple of decent and probably under-recorded grasses: Puccinellia distans (reflexed saltmarsh grass), a colonist of salted roads whose natural habitat as the name indicates is on the coast; and Polypogon viridis (water bent) a grass that been expanding in range very rapidly in urban places over the last decade or two but as yet has few Oxon records. Other aliens were in plentiful supply, particularly the invasive Myriophyllum aquaticum (Parrot's feather) which had taken over the pond on the village green.

Returning to natives, the limestone walls of the village had the usual Polypodium (polypody fern), unidentifiable at this time of year. However, a little later on once we'd got out in more semi-natural habitat we came upon a nice big stand of well-behaved Polypodium growing on a concrete bridge over a stream and which was clearly P. interjectum. As I've commented in previous posts this would seem to be our commonest Polypodium species. A little further on we came upon some lovely alder woodlands that had developed over a series of medieval fish ponds. Often getting good records is a matter of knowing what to look for in particular places, and here we managed to find the wet woodland fern Dryopteris carthusiana (narrow-leaved buckler fern), a pretty scarce plant in Oxon. Interestingly, the few recent records come from Chiltern beechwoods, an atypical habitat.

The woodlands served us well and were a nice contrast for a square that mostly comprised artificial habitats. The total for the square is now 250 taxa, a considerable improvement from the 9 it had stood at. Many thanks to those that attended.

Sunday, 3 September 2017

Aston Rowant Roses

Geoff Jones examining Rosa rubiginosa on Beacon Hill against the backdrop of the Oxfordshire plain
Late summer and early autumn is the best time to identify wild roses if one is game for the challenge. While it is a challenge, there is so much we don't know about the status and distribution of Rosa taxa in the county that their study really pays off I have found (though I am by no means an expert). I believe Geoff Jones, new to roses and a volunteer recorder at Aston Rowant National Nature Reserve, whom I met there on Saturday to spend a few hours rhodologising, has come to be of the same opinion. I will always be delighted to hear from botanists such as Geoff who are intrigued by these beautiful plants and would like to record them thoroughly. I hope the following account of our short visit will give you an idea of what could be out there to be found in your patch.

Aston Rowant NNR is of course well-known for its chalk grassland and woodlands, but it is also a very scrubby place and this is where to look for roses. Some of the scrub is very old and these are the best places to hunt for unusual roses. We started on Beacon Hill where Geoff had already puzzled over a few potentially interesting roses. In scrubby bits of downland we found several grotty bushes of two sweet-briars, Rosa micrantha (small-flowered) and R. rubiginosa (sweet-briar or Eglantine). The UK has three native species of sweet-briar — the third, R. agrestis (small-leaved), was only rediscovered in the county last year at nearby Pyrton Hill.