Saturday, 13 June 2020

Further county resurrections

This is a brief post to share some recent exciting finds of weeds in Oxfordshire. First, Anna Dudley contacted me to tell me about a population of Descurainia sophia (flixweed) that she had found at the M40 services at Waterstock. This plant was last recorded in the county in 2005 and it has always been very rare, really only a casual with us. It is a relatively common arable weed in East Anglia. If you'd like to see it, you will find it in a flower bed at SP62500478.

Surely the find of the season is Oli Pescott's discovery of a large population of Torilis arvensis (spreading hedge parsley) growing in a fallow field in Crowmarsh Gifford. This is an endangered and nationally scarce plant that had been thought to be extinct in Oxfordshire. The field is conveniently located by a footpath that passes a large number of plants at SU6171089298. The field is doubly worth a visit as there is an astonishing display of Centaurea cyanus (cornflower), another endangered arable weed, and very rare now except as an introduction. There is also Euphorbia exigua (dwarf spurge) and Filago vulgaris (common cudweed). Sadly the field is earmarked for development.

Sunday, 31 May 2020

English Botanical News and some local news

Tephroseris integrifolia at Aston Upthorpe. Kathy Warden

Cynoglossum germanicum growing at a newly discovered site, on the edge of Russell's Water Common
This is mostly a brief post to advertise the first newsletter of the BSBI's newly formed Committee for England. You can download English Botanical News from here. At a whopping 84 pages, the newsletter discusses much of interest to botanists in England and summarises recent developments from English counties. The objectives of the committee are still very much open to discussion, it having been formed in November 2019, Wales, Scotland and Ireland already having their own committees. Yours truly sits on this new committee, so if there are any (botanical) issues you feel need addressing country-wide then please let me know and I can pass them on. The newsletter includes the minutes of the first committee meeting, so you can see what is already on the table.

With the on-going restrictions on social gatherings, there is not much to report locally, though I am sure people are continuing to find nice things but not telling me.

With some of the restrictions being lifted, the Oxfordshire Flora Group's flora guardians are now able to continue their monitoring work. Kathy Warden has been searching for Tephroseris integrifolia (field fleawort) at its remaining site at Aston Upthorpe Downs in the vice county 22 part of modern Oxfordshire. Sadly it has been missing from v.c.23 for a very long time. It also seems to be much reduced on the Berkshire Downs based on Kathy's findings, but apparently it does not perform well in dry springs.

Fay Banks and I enjoyed a (socially distanced) botanical outing a fortnight ago, taking in Russell's Water, Maidensgrove and the Warburg Reserve. The latter is a honeypot site in the county but both it and the surrounding area had in fact not been well-recorded for Atlas 2020, so we had a lovely sunny walk in a beautiful part of the county, improved recording in this area (although too late for the Atlas project) and saw some great plants. The highlights included lots of the nationally rare Cynoglossum germanicum (green houndstongue) and Carex muricata subsp. muricata (large-fruited prickly-sedge). The former was a conservation introduction to the reserve in the 1990s, and which we found had spread to coppice plots around the reserve and up a lovely green lane to the common at Russell's Water.

Warburg was the original Oxon site for Carex muricata subsp. muricata (or just Carex muricata as some authorities would have it, all five members of the Carex spicata group deserving species status), found there in 2003. It particularly seems to like footpaths and we even found some at a new location a kilometre or so from Warburg, growing by the Chiltern Way footpath. Having spent a bit of time this spring comparing the different members of this locally data deficient group of sedges, it would be interesting to make a post-Atlas project out of them. See below for some comparative photos of four of the five members of the group (respectively, C. spicata, C. divulsa subsp. leersii, C. muricata subsp. muricata and C. muricata subsp. pairae).

Monday, 20 April 2020

Lockdown botany

Myosurus minimus found by Roger Heath-Brown in Garsington. Image by Roger Heath-Brown
I wonder what the ageing George Claridge Druce, great man of early twentieth century botany, did with himself during the Spanish Flu pandemic of 1918. Did he self-isolate at his home in north Oxford and work on The Adventive Flora of Tweeside (published 1919) or revisions to his Flora of Oxfordshire? Or did he potter about the town and along his local rivers, seeking the solace of wildflowers? I hope it was as sunny and floriferous for Druce and his contemporaries as it fortunately has been for us these last weeks.

I toyed with the idea of working on an (online) flora, but this seemed like too serious an enterprise for such a serious (and ridiculous) time. So, as I like to imagine Druce would have (in order not to make myself feel inadequate in comparison with his considerable industry), I have been exploring my local area more thoroughly than I have had time for in recent years. What have you been up to? I hope you have been able to get out and be cheered by spring wildflowers during your permitted exercise. A few botanists have been in touch with interesting things they've found this spring. I have had a few myself, and so I thought I'd write a blog post in an attempt to spread the cheer. Do leave a comment below if you have had a nice find you'd like to share.

Silybum marianum in a Wallingford alley. Image by Oli Pescott
First up, Roger Heath-Brown and Fay Banks separately emailed me about a new population of Myosurus minimus (mousetail) they'd both seen on their walks around Garsington. Originally found by Roger, plants were growing in a damp cattle-trodden field corner. This and similar places such as gateways are the typical habitat of this locally scarce species. Over the last few years I have also found a few new sites for this plant, all in gateways, mostly in the upper Ray, such as at Meadow Farm.

Oli Pescott tells me that on his explorations of the back alleys of Wallingford he has been finding a lot of Silybum marianum (milk thistle) and that it appears to be spreading. Over the river in the vice county of Oxfordshire, there certainly seems to be a trend also, with many recent records of a species that formerly was rather rare and casual in the county. Oli suggests that this Mediterranean native may benefit from climate change. If you'd like to see it, there is a large well-established population on the Dyke Hills at Dorchester. Do let me know if you find any elsewhere.

On her daily walk around Kidlington, Judy Webb found a plant not seen in Oxon for a long time, and only ever known from the Stonesfield area. This was the little grass Poa bulbosa (bulbous meadow-grass), which Judy found growing abundantly on a dry road verge, together with other coastal species such as Plantago coronopus (buck's-horn plantain). I wonder how it got here? With its fragile bulb-like stems, perhaps fragments were spread with mowers? It would be interesting to investigate if it is present elsewhere in the neighbourhood. I went to have look myself (on my way to do my grocery shopping) and found also a lot of Cerastium semidecandrum (little mouse-ear) growing with it, a locally uncommon or overlooked spring annual of short dry grassland (it turns brown and disappears after May).

Judy's colony of Poa bulbosa growing on a road verge in Kidlington. The plants are the yellowed patches around the edges of the verge in the left hand image. The bulbous bases are clearly visible in the image on the right. Images by Judy Webb.

Taraxacum berthae a new county record found by Judy Webb. Note the spotty leaves and adpressed outer involucral bracts. Image by Judy Webb
Like Judy and me, and other botanists stuck at home, you might have spent this period of lockdown looking at dandelions, the last few weeks being the perfect time of year for identifying these cheerful little plants. Judy's lockdown botany has continued to yield interesting plants, with her inspection of verges in Kidlington turning up a new county record, Taraxacum berthae (Bertha's dandelion). Judy shared her find of this unusual dandelion on Twitter and had it excitedly identified by keen taraxacologists Alex Prendergast and Josh Styles and confirmed by the BSBI referee. This is a rare dandelion of the north-west, so what it's doing in Oxon is a mystery. Was it introduced or could it be a relic of the old meadows that much of modern Kidlington is built on?

The fen dandelion T. palustre has for many years had a special allure for me, growing as it does in one of my favourite kinds of habitat (fenny meadows) but it has so far alluded me. Historically, there were four sites for this now endangered dandelion in Oxon, last seen in 1978. I have wanted for a number of years to look for it in the two sites that haven't been destroyed, Otmoor and Wendlebury Meads, both local to me, but I have always been too busy in April when dandelions are on show. Well, no problem with lack of time this year, and I found it surviving at both sites. It is difficult to estimate numbers since you can only really identify plants in flower and it is a small plant, but the populations seemed quite small, around a dozen flowers at Otmoor and half that at Wendlebury.

While looking for fen dandelion, I also found quite a lot of T. anglicum (English dandelion) in a different area of Otmoor, a new site, and at Wendlebury Meads growing with T. palustre, where it was last seen many decades ago. Nationally this is a much rarer dandelion but Oxford is a hotspot, with a number of sites in damp ancient meadows. My finds prompted Judy to send me a photo of a specimen she collected from Alvescot Meadows near Carterton which she thought was T. anglicum, and indeed it was (though I'm no expert). This is a significant westward extension of its Oxfordshire range.

If you are not convinced that dandelions are interesting, then I challenge you not to be impressed by the photos shown. Gorgeous little plants!

I wouldn't go as far as to say 'thank goodness for lockdown', but it's great to start the year with two county resurrections and a new county record. Fingers crossed for more good finds once this is over.

T. anglicum (top) and T. palustre (bottom) found at Wendlebury Meads. The narrow leaves and adpressed involucral bracts are characteristic of Section Palustria. The dark narrowly bordered bracts and deeply divided leaves of T. anglicum are diagnostic, the opposite situation obtaining in T. palustre with wide borders to the bracts and hardly divided leaves.

Sunday, 8 March 2020

Great bryophytes at Great Tew

Despite Storm Ciara pummelling parts of Britain, no less than five bryologists turned out for our trip to part of the Great Tew estate (the valley at the bottom of SP3730). In the event, despite getting rather wet, the valley sheltered us from the worst of the wind, and the only slightly hairy moment was the explosive crack of a branch coming down further along the valley.

Although bryologists have visited the Great Tew area previously (e.g. Eustace Jones recorded Grimmia orbicularis on the estate, and mentions a record of Orthotrichum tenellum in a "wet wood in valley north of Great Tew"  in his 1953 paper on the mosses of Berkshire and Oxfordshire), very few localised records actually exist in the database of the British Bryological Society (older records tend only to have been entered as hectad summaries). This, then, was a great chance to explore a private woodland (we had permission!) and make some localised records for an area that is not well-represented in records databases.

After picking up various common pleurocarps after dropping into the valley, we also found Isothecium alopecurum on the roots of ash and fertile Cirriphyllum crassinervium nearby on soil. Soon after we found one of the things that we had been hoping for, a tufa-forming stream emerging out of the valley-side, as is often found in cuttings and valleys on the Oolite in the north of Oxfordshire. This particular one was not particularly blessed with bryological interest, although a large stand of Palustriella commutata featured in the centre of the stream, accompanied by Cratoneuron filicinum and Pellia endiviifolia.

Palustriella commutata clump in tufaceous spring
Soon after, an uncommon sight in Oxfordshire was seen, that of Plagiomnium undulatum fruiting. Jones (1953) listed this species as "sterile" in Oxon., and still considered the fact of its fruiting "rare or very rare" after forty more years bryologising in the county (Jones, 1991).

Plagiomnium undulatum in fruit at Great Tew.
By this point of the day we were rather sodden, and thoughts were turning towards home. Perhaps the nicest thing of the afternoon was a good population of the liverwort Plagiochila asplenioides growing along a track through the wood further up the valley side. Whilst this livewort is fairly frequent in ancient woods on heavy basic soils, it is not common in Oxfordshire overall, and is always nice to see.

Plagiochila asplenioides at Great Tew.
And finally, a nice photo of the epiphytic liverwort Metzgeria violacea that seemed extremely happy in the humid environment of this hidden valley.

Metzgeria violacea

Oh, and for the non-bryologists, we also saw Dryopteris dilata growing epiphytically in the crown of a fallen oak, which is not a habitat most Floras list!

Dryopteris dilata growing as an epiphyte on oak (foreground; background fern is Polypodium interjectum)
The full list of bryophytes seen in the valley at Great Tew is given below:

Amblystegium serpens var. serpens Hypnum cupressiforme var. resupinatum Zygodon conoideus var. conoideus
Brachythecium rivulare Isothecium alopecuroides Conocephalum conicum s.str.
Brachythecium rutabulum Isothecium myosuroides Frullania dilatata
Bryum capillare Kindbergia praelonga Lophocolea bidentata
Calliergonella cuspidata Orthotrichum affine Metzgeria consanguinea
Cirriphyllum crassinervium Oxyrrhynchium hians Metzgeria furcata
Cratoneuron filicinum Oxyrrhynchium schleicheri Metzgeria violacea
Cryphaea heteromalla Palustriella commutata s.str. Pellia endiviifolia
Didymodon sinuosus Plagiomnium undulatum Radula complanata
Fissidens gracilifolius Plagiothecium nemorale Atrichum undulatum
Fissidens incurvus Rhynchostegium confertum Cirriphyllum piliferum
Fissidens taxifolius var. taxifolius Syntrichia virescens Didymodon insulanus
Homalothecium sericeum Thamnobryum alopecurum Leskea polycarpa
Hygrohypnum luridum Thuidium tamariscinum Orthotrichum pulchellum
Hypnum cupressiforme var. cupressiforme Ulota phyllantha Orthotrichum stramineum
Plagiochila asplenioides