Bryophytes of Watlington Hill

Watlington Hill is a well-known site for chalk grassland bryophytes, although, despite this, relatively few recent records are available for the area (no post-2000 records for the main monad, SU7093, are in the BBS database or on the NBN Atlas for example). However, historically the site has been well searched. Ron Porley, when at English Nature, completed a thorough survey of the Hill in the early 90s, as a part of his work on the chalk grassland of the Chilterns. Porley found the Watlington & Pyrton Hill area to be the richest of the 13 sites he surveyed in terms of chalk grassland specialist bryophytes, recording 46 of his 69 such designated species at the site (although the site was also one of the largest in terms of the area of chalk grassland, estimated at 50.9 ha at that point).

Therefore it was with high expectations that five bryologists assembled at Watlington Hill for the second excursion of the Oxfordshire mossing season (1st Dec. 2019). A number of our group were relatively new to bryophytes, so we started in the woods surrounding the main carpark, demonstrating some of the commoner feather-mosses (pleurocarps) and epiphytes (tree-dwelling bryophytes).

A gentle start to the day!

Our list rapidly swelled, with a number of epiphytes available to demonstrate, including the mosses Orthotrichum stramineum, O. affine, O. diaphanum, Cryphaea heteromalla, and Zygodon conoideus var. conoideus, and the liverworts, Radula complanata, Frullania dilatata, Metzgeria furcata and M. violacea. When I was learning bryophytes around Sheffield in the late 2000s, this would have been considered an impressive haul indeed (at that point, these species were still recolonising after having been previously eradicated from the area due to acidic pollution)! Soon after, David discovered a fallen ash with a superabundance of another epiphyte, Orthotrichum lyellii, a distinctive moss with many brown gemmae covering its leaves. Whilst we often find this on our outings, we normally only find small tufts on standing trees: no doubt our impression is biased by our vision and reach, as this supine ash demonstrated that this species can clearly become locally abundant further up trees!

Orthotrichum lyellii (middle distance) abundant on fallen ash

O. lyellii close-up, showing the brown gemmae

Progressing through the woodland along a track along the edge of the wood, a number of species typical of soil or tree roots were found. The most handsome probably being the liverwort Porella platyphylla, which tends to be found on old limestone walls, graves, hard chalky soils, and the roots of trees on such soils in the Oxfordshire district.

Porella platyphylla on beech root at Watlington.

After lunch, we emerged into chalk grassland, and most of the rest of the excursion was spent crawling around this habitat, as proven by Joshua's tweet below...

Amazing Spiderman bryologists! @sacrevert and #DavidMorris.@BBSbryology @sambbryo
Beautiful landscape too! pic.twitter.com/ilY4NGXaK8

— Joshua Ajowele (@JAjowele) December 3, 2019

A trampled path through the grassland provided us with our first chalk grassland specialists, including Microbryum curvicolle (no photo, but a nice illustration can be found here). Fissidens dubius, Weissia longifolia var. angustifolia, and the tiny stone-covering Seligeria calycina were all also found along this track or in grassland nearby, as well as several other currently infertile small cushion mosses (acrocarps). The idea of returning in the early spring was floated at this point!

Moving into a larger area of grassland on an east-facing slope, David soon located Entodon concinnus, a lovely species normally indicative of rich turf.

Entodon concinnus at Watlington

Sure enough, other species such as Trichostomum crispulum, Hypnum lacunosum and Ctenidium molluscum were all nearby. Mounting the brow of the hill, we encountered the more acid clay-with-flints that often heralds local concentrations of calcifugous species (i.e. those that prefer acid soils). Dicranum scoparium, Polytrichum juniperinum, and P. piliferum were all found in this area.

On circling back to the car park, more rich calcareous turf was found on west and north-west facing slopes, including Ditrichum gracile, Campylium protensum, Plagiomnium affine, Rhytidiadelphus triquetrus, and Brachythecium glareosum. The last was confirmed microscopically back at home, as was Brachythecium salebrosum found in the wood near the carpark at the start of the day. Other species confirmed microscopically included Bryum klinggraeffii, B. ruderale, B. rubens, Fissidens viridulus and Zygodon viridissimus. There were a number of Watlington rarities that we didn't find, but these will hopefully be targeted on the 2020 spring visit previously mentioned! The full list from the day is below.

Ditrichum gracile in chalk grassland at Watlington.

Amblystegium serpens	Fissidens dubius	Polytrichum piliferum
Barbula convoluta var. convoluta	Fissidens incurvus	Pseudoscleropodium purum
Barbula unguiculata	Fissidens taxifolius	Rhynchostegium confertum
Brachytheciastrum velutinum	Fissidens viridulus	Rhytidiadelphus squarrosus
Brachythecium glareosum	Homalothecium lutescens	Rhytidiadelphus triquetrus
Brachythecium rutabulum	Homalothecium sericeum	Seligeria calycina
Brachythecium salebrosum	Hypnum cupressiforme var. cupressiforme	Syntrichia laevipila
Bryum capillare	Hypnum cupressiforme var. lacunosum	Syntrichia ruralis var. ruralis
Bryum klinggraeffii	Hypnum cupressiforme var. resupinatum	Thuidium tamariscinum
Bryum rubens	Isothecium myosuroides	Trichostomum crispulum
Bryum ruderale	Kindbergia praelonga	Ulota bruchii
Calliergonella cuspidata	Leptobryum pyriforme	Weissia brachycarpa var. obliqua
Campylium protensum	Microbryum curvicollum	Weissia longifolia var. angustifolia
Campylopus introflexus	Mnium hornum	Zygodon conoideus var. conoideus
Ceratodon purpureus	Orthotrichum affine	Zygodon viridissimus var. viridissimus
Cryphaea heteromalla	Orthotrichum diaphanum
Ctenidium molluscum	Orthotrichum lyellii	Cephalozia bicuspidata
Dicranella varia	Orthotrichum stramineum	Frullania dilatata
Dicranum scoparium	Oxyrrhynchium hians	Lophocolea heterophylla
Didymodon fallax	Plagiomnium affine	Metzgeria furcata
Ditrichum gracile	Plagiomnium undulatum	Metzgeria violacea
Entodon coccinus	Plagiothecium nemorale	Porella platyphylla
Eurhynchium striatum	Polytrichum juniperinum	Radula complanata

Bryophyte season kicks off in the Lye Valley

In a joint effort to be more organised and transparent, this season all our meetings are on the blog calendar! We will be emailing around the details of meetings a few days in advance, if you are on David's botanical mailing list, you'll get them. If not, get in touch!

Our first meeting of the season was to the eastern suburbs of Oxford to visit the Lye Valley (SP5405), incorporating the Local Nature Reserve of the same name. This site used to be known as Bullingdon Bog, and as such is something of a locus classicus for Oxonian botany. It was, for example, the site where L'Obel made the first record of Parnassia palustris for Britain; it was recorded by Sibthorp and Boswell, and featured in early ecological work on calcareous fens by Roy Clapham (later lead author of the primary British Flora in use from 1958 up to the early 90s, when it was superceded by Stace).

A view along the Lye Valley LNR. (O.L Pescott, CC0).

It seems that we are lucky to still have the site in the reasonable condition that it is in. Eustace Jones in the early 1950s commented that "Bullingdon Bog which must once have been an ideal example of a calcareous valley bog, is now a disturbed fragment lying in the middle of an Oxford housing estate, and obviously cannot survive much longer." Although the site was scrubbed over in recent years, and the valley sides slumping due to scouring of the valley bottom by a storm drain outflow directed along the stream, excellent management work has taken place in recent years, and is gradually restoring the valley mire to its former glories (thanks to David Morris for this information).

Bryologists assemble! (O.L. Pescott, CC0).

But to the bryophytes! We dropped into the valley from Coverley Road, recording the woodland and along the stream before the beginning of the LNR proper. Many common species were quickly found, including Tortula subulata on friable soil, and Rhyncostegiella tenella on stone. Along the stream the thallose liverworts Lunularia cruciata and Pellia endiviifolia were growing in close association at the bottom of a concrete embankment. An odd amblystegioid growth was also scraped from concrete, which, under the microscope, seemed to match descriptions of the coastal variety of Amblystegium serpens var. salinum. This, however, would be an odd turn-up for Oxford, and must await confirmation from the BBS Recorder for Mosses! Subsequently an old Hawthorn turned up a rich crop of epiphytes, including the ever expanding (and beautiful) species Orthotrichum stramineum and Syntrichia papillosa. An uncertain Ulota was later checked at home, but turned out to be the commonest taxon (at least locally) U. bruchii.

After lunch the reserve proper was tackled, and a new list was begun to ensure that records made would be traceable directly to the LNR. Many epiphytes and common species were again quickly added, including a number that chose to grow on the synthetic wood of the reserve boardwalk (Syntrichia latifolia, S. montana, S. virescens, Orthotrichum affine, O. diaphanum, among others). Next was the fen proper, and many of our expected species began to accumulate (Plagiomnium elatum, Cratoneuron filicinum, Palustriella commutata, P. falcata, Campylium stellatum, Fissidens adianthoides etc.) All previously known from the mire, but all lovely to see thriving. The curious epiphyte Platygyrium repens was also found on a pollarded willow along the stream. Deciduous branchlets of very fine leaves give this species a fuzzy appearance in the field.

Platygyrium repens at Lye Valley. (O. Pescott, CC-BY).

Some known species we failed to refind (e.g. we did not relocate Drepanocladus revolvens or Climacium dendroides), but many other species were added to the site list. A productive day, and a good start to the season.

The list of unique species seen was as follows:

?Amblystegium serpens var. salinum	Platyhypnidium riparioides	Brachythecium rivulare
Amblystegium serpens	Rhynchostegiella tenella	Bryum pseudotriquetrum
Barbula convoluta var. convoluta	Rhynchostegium confertum	Calliergonella cuspidata
Barbula convoluta var. sardoa	Schistidium apocarpum s.l.	Campylium stellatum s.str.
Brachythecium rutabulum	Syntrichia laevipila	Cirriphyllum piliferum
Bryum capillare	Syntrichia papillosa	Ctenidium molluscum
Bryum moravicum	Tortula muralis	Dicranoweisia cirrata
Cratoneuron filicinum	Tortula subulata	Didymodon fallax
Cryphaea heteromalla	Ulota bruchii	Fissidens adianthoides
Didymodon sinuosus	Zygodon conoideus var. conoideus	Fissidens incurvus
Fissidens bryoides	Cololejeunea minutissima	Orthotrichum lyellii
Fissidens taxifolius	Frullania dilatata	Palustriella commutata s.str.
Homalothecium sericeum	Lophocolea heterophylla	Plagiomnium elatum
Hypnum cupressiforme var. cupressiforme	Lunularia cruciata	Plagiomnium undulatum
Hypnum cupressiforme var. resupinatum	Metzgeria furcata	Syntrichia latifolia
Kindbergia praelonga	Metzgeria violacea	Syntrichia montana
Orthotrichum affine	Pellia endiviifolia	Syntrichia virescens
Orthotrichum diaphanum	Radula complanata	Thamnobryum alopecurum
Orthotrichum stramineum	Platygyrium repens	Cephalozia bicuspidata
Oxyrrhynchium hians Oxyrrhynchium schleicheri	Palustriella falcata	Lophocolea bidentata

Autumn recording

Rosa sherrardii at Meadow Farm. The main features visible are the forward-pointing sepals and strong straight prickles.

A full press, product of looking at roses at Meadow Farm

With the coming of the season of mellow fruitfulness, I have of late been thinking about all those brightly-coloured berries, drupelets, drupes, haws, hips and pommes in hedgerows and scrubby places. As readers familiar with my interests will anticipate, this has mostly focused on roses, but I have also been scratching my head over hawthorns and having a go at brambles. This blog post is about what I have been finding this autumn.

Roses were the main target for a recording meeting I ran at Meadow Farm Nature Reserve in Blackthorn. The highlight was Rosa sherardii (Sherard's downy-rose), a predominantly northern and western species which has largely disappeared from our area (see map below). Gareth Knass recently found it on the downs in the VC22 part of modern Oxfordshire, but except for the one bush at Meadow Farm I am not aware of any confirmed recent records for VC23. I have only otherwise seen the hybrid with R. canina from VC23 (R. x rothschildii, e.g. at Sydlings Copse). Gareth has taken many wonderful photos of roses — you can see his images of R. sherardii here.

We also found the hybrid between R. canina (common dog-rose) and R. micrantha (small-flowered sweet-briar) (R. x toddiae), which seems to be the first record for VC23 since 1930. There were also R. canina hybrids involving R. obtusifolia and R. tomentosa, which are quite widespread, as well as R. obtusifolia itself, which seems to be a more local plant. Other unusual hedgerow things included a big specimen of Salix cinerea subsp. cinerea, quite an uncommon plant in Oxon.

Oli Pescott and I spent an afternoon looking at roses around Hills Watlington, Pyrton and Shirburn on the Chiltern escarpment, another good area for roses (I blogged a couple of years ago about the rich rose flora at Aston Rowant). One of the most characteristic species is the downland rose R. rubiginosa (sweet-briar), which is quite uncommon as a native plant but is widely planted in hedgerows. With its strong apple smell, big hips with forward-pointing sepals and fiercely-armed stems it is one of the more straightforward species to identify. Oli and I also found a number of bushes at Watlington and Pyrton that at first looked like R. micrantha but that on closer inspection had a few small slender prickles (acicles) toward the ends of the flowering branches and irregularly-sized hips — these were the hybrid with R. rubiginosa. This was only recently found in Oxon, from Sydlings Copse, but these new finds suggest it may be more widespread.

Roses aren't all about hybrids, though they are certainly very common, and Oli and I saw a fine bush of R. tomentosa (harsh downy-rose) at the edge of Shirburn Wood. Recording for Atlas 2020 seems to have shown that this species is more common than previously indicated but that it is largely confined to the Chilterns, downy roses in the rest of the county being hybrids. We also had time to pay homage to the nationally scarce R. agrestis (small-leaved sweet-briar) at Pyrton Hill, which was rediscovered in the county in 2016.

Crataegus x subsphaerica at Watlington Hill (note the forward- directed sepals)

I have written a few times this year about about non-native shrubs that look similar to native species. So far, however, I have not introduced the non-native hawthorns. This was mainly because I hadn't seen many examples in Oxon, but this autumn I have seen quite a lot, and I encourage others to have a look while these things are at their most conspicuous. There are two taxa to look out for, Crataegus rhipidophylla (large-sepalled hawthorn) and its hybrid with C. monogyna which is called C. x subsphaerica and is the more commonly planted taxon (whether we also have the hybrid with C. laevigata I don't know). I have seen bushes of C. x subsphaerica that are pretty old so this taxon is likely to have been with us for a long time — there seems to be a lot of introgression with C. monogyna, which must explain why these things have been over-looked. Some bushes I have found can only have arisen from bird-sown seeds, so it may be widespread and not just confined to planted hedgerows.

As you will have guessed, the conspicuous features are the haws, which are larger than usual and the sepals stick up from the fruit. The haws are often a brighter shade of red than C. monogyna and more square-shaped. If you look at haws of C. monogyna you will see that the sepals are reflexed so that they lie against the haw and the sepals are short triangles with blunt tips — if you see a hawthorn with some haws with erect sepals and the sepals longer than wide and verging on acute, then you are probably looking at C. x subsphaerica. The leaves of this hybrid are similar to C. monogyna, though they are heterophyllous, and one can usually find some leaves that are broader toward the base and have more teeth, features of C. rhipidophylla. True C. rhipidophylla has leaves that look like similar to Sorbus torminalis (wild service tree). The descriptions and keys in the books suggest the differences are subtle but really they are quite striking, so don't be deterred!

The photograph to the right gives a good idea of what to look for. David Broughton has also blogged about hawthorns and has some good images — see here.

Atlas recording in Sutton

After a pretty ordinary Atlas recording session a fortnight ago, on Sunday we had a return of luck and the big lists of earlier in the season. Expecting again ordinary countryside around Sutton (SP40D), we were rewarded with over 320 taxa, a list that included many interesting native plants but that of course was boosted significantly by garden escapes and other aliens. As last time, I will single out the native look-alike shrubs in the hope that this will generate more records and demonstrate that these things are ubiquitous (last time we were far away in SP42F). Maybe I should put together a key to these things — if you'd find this useful or interesting then leave a comment below and I might consider it!

If you look in the floras and the literature about native look-alikes, you'll see that there is an alien taxon for just about every native hedgerow and woodland shrub in Oxon, and some, like the dogwoods I blogged about last time, have several. This meeting it was the turn of the guelder roses, a commonly planted hedgerow shrub (entirely inappropriately, the native Viburnum opulus being largely a plant of damp woods) and of which Sell and Murrell describe two non-native forms of the native species and two similar alien species. My practice had been to lazily assume that planted things were at least the native species, if perhaps cultivars, but confronted with strange-looking plants in the Sutton area I had to revisit this assumption. The native guelder rose is an elegant plant with quite thin yellow-green small and neatly toothed leaves — if you see anything with thicker or darker or larger leaves with strange shapes then consider V. sargentii (Asian guleder-rose) and V. trilobum (American guelder-rose). I think we had both on Sunday, new to the county but doubtless overlooked elsewhere. V. trilobum has odd-looking thick-stalked glands on the petioles (I had never even noticed that guelder roses had glands!) and the leaves on the upper parts of branches have the middle lobes longer than wide. V. sargentii is similar to V. opulus with sessile glands and the middle leaf lobes as long as wide or less, but the leaves are thicker and darker and less toothed (some other differences are also described in Stace and Sell and Murrell).

Continuing with aliens, but aliens we botanists are prepared to tolerate and even admire, we also had a good variety of arable weeds. A fallow field sported no fewer than five species of Chenopodium, with the common C. album (fat-hen) and C. polyspermum (many-seeded goosefoot), the less common C. rubrum (red goosefoot) and the quite scarce C. ficifolium (fig-leaved goosefoot) and C. hybridum (maple-leaved goosefoot). We also had Euphorbia exigua (dwarf spurge), both species of Kickia (fluellens) and the fairly rare Polygonum rurivagum (cornfield knotgrass). I wouldn't be surprised if the latter were a little under-recorded — look out for its eye-catching dark pink tepals and narrow leaves (sorry for not taking a photo).

We did quite well for aquatic plants too. A new pond had Potamogeton crispus (curled pondweed) and P. berchtoldii (small pondweed), and the aquatic liverwort Riccia fluitans which I had never seen in Oxon. Other waterbodies turned up Zannichelia palustris (horned pondweed) and four species of Lemna (duckweeds).

I can't touch on aquatic plants without announcing Judy Webb's excellent pondweed find last year, and which I visited last week because I couldn't quite believe it. I shall deliberately not reveal the exact location of the site, but it would be hard to believe that just about any location in Oxfordshire would be suitable for Potamogeton polygonifolius (bog pondweed) these days. A plant of acid waterbodies and wetlands, it was known once-upon-a-time from Shotover Hill and a small number of other sites with the acid geology that is rare in the county, but had not been seen for decades. Yet there it was, growing in a former limestone quarry with plants of mineral-rich wetlands, like Schoenoplectus tabernaemontanii (grey clubrush) and the moss Campylium stellatum. The national pondweed referee Chris Preston was sensibly circumspect in not confirming the identification from my photographs, but I am happy to announce it now and possibly be proven wrong!

All of the above shows how dynamic our flora is, perhaps a theme of many of my posts on this blog. With people constantly disturbing and changing the environment and many plants good at dispersal and able to take advantage of this (naturally or because we find them attractive or otherwise useful), it is important and fascinating to record these changes and underscores the value of projects like Atlas 2020. So, please keep those records coming!

Recording at Glympton

A highlight of the BSBI ASM, Polygala amarella (dwarf milkwort)

It has been over a month since I last blogged and amazingly that was the last time I organised a meeting and did any serious recording in Oxfordshire! I have been botanizing, of course, with a highlight being the BSBI's Annual Summer Meeting which you can read about on the News and Views blog, including posts from yours truly. It might not have contributed to Atlas 2020 in Oxfordshire but it was awfully fun and will have made a big difference to Mid-West Yorkshire which needs records more than we do!

Anyway, this last Sunday I finally managed to find some time in the diary for a recording meeting, and I met up with three other locals at Kiddington. Just in time I had been reminded by Sally Abbey that her recording group had already been there this season, so rather than repeat their work we recorded a tetrad to the east of Kiddington, taking in the lanes, farmland and woodland of Glympton (SP42G). It was a fairly ordinary square without the many lovely highlights of previous meetings this season, but we hit the target of 200 taxa that makes me feel like it was worth going out. A few odd things were found, mostly plants that are likely under-recorded.

One such was the hybrid bindweed Calystegia sepium x silvatica (=C. x lucana), which I am not sure I have ever noticed before. Apparently it is a variable hybrid, but our plants had large flowers like C. silvatica (large bindweed) but with the bracts below the flowers only slightly overlapping and not pouched (as they would be in C. silvatica), and the leaves small, intermediate in shape between C. sepium (hedge bindweed) and C. silvatica (the latter has a broad sinus with a truncate base, the former a narrow sinus with an acute base, as illustrated in Polland and Clement). Another odd plant was Bromus commutatus var. pubens, which looks all the world like the usual meadow brome (var. commutatus) but has shortly pubescent spikelets. As I have described in previous posts, B. commutatus is likely a common cereal weed in Oxon but is significantly under-recorded, probably because botanists think of it as a plant of meadows.

Finally, something must be said about the hedges in the Glympton area, as they were the worst I have seen in Oxon for in-filling and re-planting with alien shrubs sourced from nurseries that should know better. Mile upon mile was full of non-native dogwood and spindle and questionable field maple and hawthorn, presumably on land belonging to the same estate. The dogwood which was the main component of many hedges was a great beast with enormous leaves — I think it was Cornus koenigii (Asian dogwood), a first for the county, rather than the more usual C. sanguinea subsp. australis from south-east Europe and which also often has large leaves. It'd be marvelous if other recorders could be mindful of alien shrubs in hedges and send me records. Planting these shrubs for housing, roads and other developments as well as countryside hedges has become very common and could come to affect our native scrub vegetation, so we need the records to understand potential future change. To encourage records, here's a key to Cornus taken from Sell and Murrell Volume 3.

1.	Hairs on underside of leaves mostly curved upwards and basifixed *	2
1.	Hairs on underside of leaves mostly adpressed and medifixed **	3
2.	Leaves 4-9 x 2-6cm	C. sanguinea subsp. sanguinea
2.	Leaves 5-13 x 2.5-7.0cm	C. koenigii
3.	Leaves with 2–4 pairs of veins; drupes black	C. sanguinea subsp. australis
3.	Leaves with 4–7 pairs of veins; drupes white or bluish ***	4
4.	Twigs bright yellow or bright red in autumn and winter	5
4.	Twigs becoming dark brownish-red in autumn	6
5.	Twigs becoming bright yellow in autumn and winter	C. alba var. flaviramea
5.	Twigs becoming bright red in autumn and winter	C. alba var. sibirica
6.	Plant not stoloniferous; leaves 5–15 × 3–10 cm	C. alba var. alba
6.	Plant stoloniferous; leaves 4–9 × 2.5–6.0 cm	C. sericea

* Bend the top of the leaf over your finger and hold it up to the light - you will see the hairs sticking up. Under a lens the hairs look like they have one arm, or if there appear to be two it is two hairs arising from the same point rather than a single medifixed hair.
** Bend the top of the leaf over your finger and hold it up to the light - you will see no or few hairs. Under a lens the hairs look like they have two arms, with both mostly pressed against the leaf.
*** The two remaining species look very different from the previous three and populations are usually very obviously of horticulutral origin, e.g. landscape plantings, garden rubbish. C. sericea can be invasive of damp woodland.

Rousham and Oxford Canal

Equisetum x litorale with the tall wide stems of E. fluviatile and whorled filiform branches of E. arvense. O.L. Pescott.

Another haul of excellent records from this weekend, when we were out botanising again in the north of the county. This time we returned to the Cherwell valley and Oxford canal in SP42, where a few meetings were held back in 2017. We met at the church on the Rousham estate, the plan being to quickly look round the churchyard and then head east to fill in a blank square (SP42W) along the canal. However, having parked in a silly place and been confronted by the farm manager, we were very kindly invited to some unplanned botanising of private parts of the estate — how could we resist? Although in the opposite direction and a different tetrad to that planned, it turned up some good wetland plants, including

Dactylorhiza praetermissa

(southern marsh-orchid) and the diminutive pondweeds

Potamogeton pusillus

(small pondweed) and

Zannichellia palustris

(horned pondweed). We also found the hybrid horsetail

Equisetum arvense x fluviatile (=E. x litorale)

(shore horsetail), which as far as I know hasn't been recorded in the county since 1982.

Having bumped up the tetrad records from Rousham (SP42S) and nearby (SP42R), we marched off to Lower Heyford to pick up the canal. Passing through the station (SP42X) we came upon an acquaintance from a previous meeting in the Cherwell valley, another hybrid, the dock

Rumex conglomeratus x obtusifolius (=R. x abortivus)

. The dense widely branched leafy infloresence was eye-catching and the tepals were intermediate in shape. Not a beautiful plant, but attractive in a Rumex sort of way. Surely under-recorded, this is one to look out along our river floodplains.

The Oxford Canal was productive for a range of common wetland plants. Although churned up by boats, the vegetation is less eutrophic than most of our rivers, with plants such as

Carex paniculata

(greater tussock sedge) common along the canal. Wet woodland and damp grassland by the canal provided more

C. pseudocyperus

(cypress sedge) and hundreds of

Dactylorhiza fuchsii

(common spotted-orchid). We had more hybrids, with the willow

Salix caprea x viminalis (=S. x smithiana)

and the woundwort

Stachys x ambigua

. Great to find the latter again this season after we had it at South Newington in May — with very few recent records could it be under-recorded?

The highlight from the canal was

Potamogeton lucens

(shining pondweed), growing in quite a large colony with the much commoner

P. pectinatus

(fennel-leaved pondweed). Always exciting to find a good Potamogeton and catch a glimmer of the former glory of our waterways. Thanks to Oli (pictured left) for being well-equipped with homemade grapnel.

By the end of the meeting I think all our legs were feeling tired, having walked back and forth through five tetrads. With our efforts divided we didn't get the impressive tetrad totals of previous meetings but we gathered over 500 records. Having seen more than 330 taxa the plants were certainly worth the mileage.

Broughton Casttle

The first meeting of June and the fifth of the season was held last weekend at Broughton Castle near Banbury. This site had been recorded previously for Atlas 2020 but we had special permission to botanise the whole park and therefore hoped to refind some of the plants historically recorded but not seen since 2000.

I had particularly hoped that we might find some of the nice aquatic plants that had been recorded from the Castle Moat. As it turned out the moat was a brown soup with very few macrophytes, an unpleasant appearance completed by floating dead freshwater mussels. The Sor Brook was no better, sporting also the invasive non-native aquatic plant

Egeria densa

, the first reported sighting of this plant in Oxon for 35 years. Tributaries of the Sor Brook had some other infamous beasties, with

Fallopia sachalinensis

(giant knotweed) and its giant handkerchief-like leaves and

Heracleum mantegazzianum

(giant hogweed). On a positive, we did find quite a lot of

Ranunculus fluitans

(river watercrowfoot), which was good to see.

Elsewhere in the park plant diversity was quite limited. There was a decent stand of calcareous grassland with plants like

Cirsium acaule

(dwarf thistle),

Koeleria macrantha

(crested hair-grass) and

Helianthemum nummularium

(common rock-rose), but these had all been recorded previously. In all we managed to find about 250 taxa, bumping up the tetrad total to 338 from 252. Not the enormous haul of records of previous meetings, but eminently respectable and goes to show that even in well-recorded tetrads there is always more to find.

Interesting things have been turning up elsewhere in the county this spring. I was contacted independently by Frank Hunt and Andrew Lack after they both found a new population of

Scandix pecten-veneris

(shepherd's-needle) near Sandhills, north-east of Oxford. Frank also found a new population of

Montia fontana

(blinks), surprisingly at the well-botanised North Leigh Common. This time of year always produces some sore heads when the marsh orchids come out, and surveying a meadow in the VC 22 part of modern Oxfordshire Judy Webb and I found what with the help of BSBI Dactylorhiza referee Ian Denholm we determined as a swarm of

D. maculata

(heath spotted orchid),

D. praetermissa

(southern marsh orchid) and their hybrid D. x hallii. The latter was new to VC 22 and the modern county.

Botanising less obviously delightful places for Atlas 2020 near Adderbury, I found

Viola tricolor

(wild pansy) and, along the Oxford Canal,

Lepidium heterophyllum

(Smith's pepperwort). According to the Flora of Oxfordshire the latter has not been seen in the vice county since 1983! Not far away was possible Galium parisiense (wall bedstraw), but I want to check the fruits to be sure. This has not been seen in Oxon before, but was recently found new to Northants (VC 32), in the VC 32 part of Banbury and elsewhere.

The excellent Oxfordshire's Threatened Plants published last year reported that the small annual

Minuartia hybrida

(fine-leaved sandwort) had gone the way of many such plants and was extinct in Oxon. Fortunately not so, as the population known historically from the old chalk pit in Chinnor is still there, found by Paul Stanley back in 2013 and also seen by Oli Pescott, David Roy and myself while recording around Chinnor. The old pit has many other interesting plants, so do go and see this little delight while it is still out.

The Barfords

Carex rostrata (bottle sedge) growing in an artificial pond

Sunday continued the run of highly successful Atlas 2020 recording meetings in north Oxfordshire, when as a a fortnight ago we had another haul of 300+ taxa. Three of us met at Barford St Michael, downstream along the River Swere from where we last met, but it was a disappointing start, the churchyard of St Michael's proving among the dullest I have yet visited in Oxon. We later visited St John's in the same tetrad (SP43G), but it was even worse. However, we did find a single plant of

Rumex pulcher

(fiddle dock) in St John's churchyard, identifiable despite having been mangled by mowing, and last recorded there in 1989.

This tetrad was on my list of priority squares for Atlas 2020, with almost no post-2000 records and several locally rare plants reported in the Flora of Oxfordshire that are the only historic localities for these plants in the hectad (SP43), e.g.

Carex rostrata

(bottle sedge) and

Triglochin palustris

(marsh arrowgrass). As with previous meetings, therefore, the goal was to fill in this gap in the tetrad map and re-find plants for the hectad. As other recorders have found, relocating old records can be very difficult, with most records from the Flora available only as digitised card indexes with no locality information other than tetrad or hectad. Therefore, do remember that in order that future botanists do not have to share in this frustration, it is important that if you find a plant that is uncommon in the county, or even just within the tetrad you are recording, that you record a precise locality.

I had not realistically expected that we would refind many of the rarer plants, and as we were not spoiled with habitats as wonderfully plant-rich as last time, serious leg work was required to cover as much potentially productive ground as possible. As last time most of the good habitat was located along the River Swere, particularly a small area of wet grassland around a spring, home to the Triglochin we sought, as well as other wetlands plants such as

Caltha palustris

(marsh marigold),

Stellaria alsine

(bog stitchwort) and

Valeriana officinalis

(common valerian). The nearby floodplain of the Swere had

Carex nigra

(common sedge), also on my hectad wanted list,

Myosotis discolor

(changing forget-me-not) and other commoner floodplain plants.

I had assumed that the historic record of

Carex rostrata

would have been from the floodplain also but doubted there would be anywhere wet and unpolluted enough to still have it. As it was it we turned it up growing in abundance in a pond formed by damming of a small tributary of the Swere. Where did these plants come from? Willows along the edge of the pond, however, had clearly been planted, and included several quite large specimens of

Salix pentandra

(bay willow), a rare willow in Oxon and also on my hectad wanted list. Growing in pasture nearby was a bedstraw that had the habit of

Galium album

(hedge bedstraw) but with leaves on the narrow and suspiciously parallel side for this species — surely, the hybrid with

G. verum

,

G. x pomeranicum

? Some came home with me to see if it will produce the intermediately-coloured flowers that would clinch this determination. Although records indicate that it has always been rare in the county, do keep an eye out for this distinctive plant in meadows and pasture on calcareous soils.

A couple of closing thoughts on other harder to identify plants. Now is the best time of year to find and identify members of the

Poa pratensis

aggregate, with both

Poa angustifolia

(narrow-leaved meadow-grass) and

Poa humilis

(spreading meadow-grass) recorded on Sunday. Though quite distinctive plants (especially

P. angustifolia

) they are only really obvious in spring and early summer after which they are swamped by taller things — see the Plant Crib for descriptions. Finally, roses will be coming into flower over the next couple of weeks and one can start to provisionally put names to bushes (e.g. we had

Rosa obtusifolia x canina

on Sunday). It would be really great to have some more rose records for Atlas, so if you find a rose that might be a bit different (mainly things with glands and hairs) then do take photographs and I can provide some advice — the things to look for are summarised in the BSBI Yearbook under the referees section or in the roses handbook. You can see what roses have been recorded in your area by looking in the tetrad lists available via the Atlas progress map.

Note: The next meeting will be on June 1st, which is a Saturday rather than the usual Sunday. We have been given permission to explore the grounds of Broughton Park — please email me if you would like to come along.

South Newington

Note: I have added a new function for the blog — hover over a species' scientific name to see a map of its current tetrad distribution in vice county 23. The data come live from the BSBI Distribution Database.

Above: grassland on the valley slope above the River Swere, with abundant Poterium sanguisorba. Several spikes of Carex caryophyllea are also visible. D. Morris. Below: Equisetum fluviatile and tussocks of Carex actua and C. paniculata growing in the pond. O. Pescott.

The numbers of botanists attending my recording outings continues to dwindle, with just Oli Pescott and myself meeting in South Newington last Sunday. However, what we lacked in people we made up for in plants, the tetrad (SP43B) yielding the richest crop of any recording meeting I have organised over the last few years. Meetings in this area continue to demonstrate that though this part of the Cotswolds may be far away for many of us it is well worth the journey (lifts can be arranged!).

As is traditional, we started with the local churchyard, unusually dedicated to St Peter ad Vincula, which proved to be among the better of those we have visited recently. Half of the churchyard had been left uncut and was covered in

Ranunculus auricomus

(goldilocks buttercup) and there were other typical churchyard plants such as

Leontodon hispidus

(rough hawkbit) and

Saxifraga tridactylites

(rue-leaved saxifrage). Exploring the village afterward, we had fun deciding whether members of the garden flora had gone sufficiently wild that we could record them — some such as

Geranium sanguineum

(bloody cranesbill) only just made it onto the list.

The River Swere meanders through South Newington, and the valley of this small tributary of the Cherwell north-west of the village provided a feast of native plants. We spent several hours exploring a fabulous meadow in the main valley and a wooded valley of a tributary to the north (both accessible by footpaths). The meadow sported an abundance of wildflowers, including drifts of

Conopodium majus

(pignut),

Geranium pratense

(meadow cranesbill) and

Poterium sanguisorba

(salad burnet), and numerous local species such as

Avenula pratensis

(meadow oat-grass),

Carex caryophyllea

(spring sedge),

Hypericum maculatum

(imperforate St John's-wort) and

Polygala vulgaris

(common milkwort), of which C. caryophyllea and P. vulgaris were new for the site and on my Atlas 2020 hectad wanted list. There were numerous other sedges in the meadow, particularly in a former course of the Swere, where we found

C. actua

(slender tufted-sedge),

C. acutiformis

(lesser pond sedge),

C. paniculata

(greater tussock-sedge) and

C. riparia

(greater pond sedge).

Exploring the valley to the north, we found large colonies of

Scirpus sylvaticus

(wood club-rush) along a stream and around springs, as we did earlier this spring.

Neottia ovata

(common twayblade) was on my Atlas 2020 wanted list for the hectad — it had not been seen in this tetrad before but the site looked suitable and we managed to find a single plant. Some other highlights included

Salix purpurea

(purple willow), another new species for the tetrad, and the hybrid woundwort

Stachys palustris x sylvatica (=S. x ambigua)

, which I had never seen before but which Oli knew from up north where it is more common. There are hardly any records of S. x ambigua from Oxon, so this was a particularly good record.

I had aimed to visit another site but I forgot how to get there, but exploring the lanes of South Newington turned up further nice plants such as

Helianthemum nummularium

. The site would have added a few more species to our list but as it was we returned to South Newington with a list of over 300 taxa and very happy botanists! The tetrad is now very well recorded and we recorded several species that can be really quite difficult to relocate once they have been missing from a hectad for some time, so an excellent contribution to Atlas 2020.

Scirpus sylvaticus. O. Pescott

Bloxham Atlas recording

It's already time for me to write another blog post about another Atlas recording meeting, held last Sunday. With fortnightly weekend meetings (listed in the events calendar), can I keep this up all season?

Sunday's meeting was in an even further flung corner of the county than the previous meeting. Three of us met at St Mary's church in Bloxham (SP43H), a rather grand edifice for a parish church. The churchyard further confirmed my experience that unimproved but heavily mown churchyard grassland in Oxon is characterized by a small number of hangers-on, species like

Leontodon hispidus

(rough hawkbit),

Plantago media

(hoary plantain) and in spring often

Ranunculus auricomus

(goldilocks buttercup). It was perhaps a little early in the year to be absolutely confident of the potential

Epilobium lanceolatum

(spear-leaved willowherb) which Oli Pescott found — definitely worth a visit later in the year to verify whether it was this locally rare willowherb. After the church we botanised the local streets, picking up spring annuals like

Saxifraga tridactylites

(rue-leaved saxifrage) and a host of garden escapes, such as the unusual

Geranium x magnificum

. We also found

Petroselinum segetum

(corn parsley), which is not that uncommon around Oxford but which hasn't many recent records from the north of the county.

In addition to its being hardly recorded, the main attraction of SP43T had been The Slade, a former BBOWT nature reserve and now an official Local Nature Reserve (LNR) managed by the parish council. This spring-fed site had once supported such wetland delights as

Molinia caerulea

(purple moor-grass), so although these had not been seen at the LNR for a long time it nevertheless looked enticing. We did not succeed in refinding any old wetland rarities but did turn up

Dactylorhiza fuchsii

(common spotted orchid),

Hypericum maculatum

(imperforate St John's-wort),

Silene flos-cuculi

(ragged-robin) and a lot of Rosa arvensis x canina (=R. x irregularis). This hybrid rose is very distinctive when growing in sunny places: looking like R. arvensis (field rose) on speed, it forms dense and often very extensive thickets with more robust stems than is usual in R. arvensis and many of the hips are small, black and abortive. Possibly R. x irregularis is under-recorded as I find it quite often, usually in more open places than is usual for

Rosa arvensis

.

The last nice plants of the day came from some hands-and-knees work in very nibbled sheep pasture, where we managed to find some small patches of

Saxifraga granulata

(meadow saxifrage). It was not quite in flower but was nevertheless great to see. On the whole we had to work quite hard for our records, so I was surprised to find after entering the data that we'd recorded 253 taxa (albeit with quite a lot of aliens), putting the post-2000 total to 297 — a valiant effort!

The next Sunday recording meeting will be on 12^th May. It'd be great to have more botanists along — hopefully the last two blogs have shown that there are plants up in the north of the county worth travelling for!

Tetrad distribution of

And so it begins

The first recording meeting of the final season of Atlas 2020 in Oxfordshire was on Sunday. Meeting in Nether Worton in SP43, the location was evidently a little out of the way as there were only four of us, but if you thought that then you missed out on good botanising. Rather than the more usual square-bashing strategy, the aim of this meeting was to record an already quite well-recorded area in order to improve it further and also to pick up some plants that have not been seen this century in the hectad in Oxon, such as the woodland plants Viola reichenbachiana (early dog-violet) and Melica uniflora (wood melick). Previously these areas had been visited later in the year and we were therefore sure to pick up new things.

We started at the churchyard of the tiny church of St James' in Nether Worton (SP43F), a tetrad with a respectable post-2000 total of 168 but some missing vernal species. The churchyard was pretty undistinguished, with typical hangers-on of heavily-mown churchyard grassland such as Plantago media (hoary plantain) absent. There were plenty of naturalised non-natives to lend colour though, such as Cerinthe major 'Purpurescens', an annual bedding plant from the Mediterranean which appeared to have seeded from the adjacent garden and was a first for the county. There were also many plants of Ranunculus auricomus (goldilocks buttercup) here and in the nearby verges. We didn't stay long in the tetrad due to lack of promising-looking land accessible by footpaths, and instead headed west toward the Great Tew Estate via a detour north over Iron Hill Down (SP43A).

After a few kilometers on Iron Hill Down I was feeling pretty desperate as the place was an arable wasteland, though there were some springs with a few common wetland plants in one area. Crossing the B4031 south into the Great Tew Estate the spirits lifted, however, with a flurry of ticking of semi-natural woodland and grassland plants, like Sanicula europaea (sanicle) and Poterium sanguisorba (salad burnet). Thinking aloud I suggested that some nice grassland looked perfect for Ophioglossum vulgatum (adder's-tongue fern) and then promptly found several of the tiny fronds of this lovely vernal fern. Turned out this was a new hectad record!

Continuing into the valley bottom toward Great Tew we came upon a series of wet woodlands with springs and streams. Here we found a small population of Scirpus sylvaticus (wood club-rush), a scarce plant in Oxon. As a species of feruginous wet woodlands, this north-western part of the county with its iron-rich limestone is the main area where it has historically been recorded. The population we found was first seen in 2015. Some of the other highlights of this area included Polystichum aculeatum (hard shield-fern) and Hypericum maculatum (imperforate St John's-wort).

We concluded the meeting back in Nether Worton with a pretty diverse haul of records for early April. In total we collected 340 records of 236 taxa: 197 in SP43A and 127 in SP43F. This put the tetrad totals up from 214 to 284 in SP43A and from 168 to 214 in SP43F. Certainly better than I was anticipating after a pretty dismal morning! The next meeting will be on 21st April — I hope you can join me.

Botanical advertisements

A short post to advertise a couple of items of interest.

First, on Sunday 7th April (that's this coming weekend) I will be leading the first of my 2019 recording meetings for Atlas 2020. We will be meeting at St James' church in Nether Worton (SP 426 300) at 1030 - please email me if you would like to come. These meetings are a great way to learn to identify plants, get to know the county's flora and meet other botanists. They will be held fortnightly throughout the season (unless I get overwhelmed with work as in previous years, but that's the plan for now). See the events calendar for future dates.

Second, former county recorder and Oxfordshire Flora Group member Sue Helm asked me to advertise a new book published by her husband Professor Dieter Helm, Green and Pleasant Land. If you attended the OFG conference a few years ago you will remember Dieter's excellent talk about the economics of natural capital, the subject of his previous book Natural Capital: Valuing The Planet, Plants might not be the subject of Dieter's books (though a favourite of Sue's Viola kitaibeliana (dwarf pansy) gets a few mentions in Natural Capital if I remember rightly), but plants are an example of what he calls 'natural capital' and according to Dieter it is our failure to account for these assets that has lead to the destruction of so much of our flora, among other wildlife. His new book is already on my pile of 'to read' books, and I am sure it will contain many thought-provoking ideas relevant to plant conservation, if in a rather different way to that which we are used to thinking about conservation.

The Year in Botany

We are well into 2019 but I am only just getting round to writing my now traditional OxBot 'Year in Botany'. It may have been a bit of a poor year for blog posts, but 2018 was another good one for botanising in Oxfordshire.

In terms of botanical highlights, many came at the beginning of the season. As summarised in previous posts, new populations of Eriophorum angustifolium (common cottongrass) and Oenanthe silaifolia (narrow-leaved waterdropwort) were found this year, Cystopteris fragilis (brittle bladder-fern) was refound for the county, and there was the strange case of Althaea officinalis (marshmallow) appearing at Otmoor. There were also new sites for other rare plants such as Myosurus minimus (mousetail) and Gymnocarpium robertianum (limestone fern). Recording also turned up new sites for the acid-loving species Juncus bulbosus (bulbous rush) in the Chilterns and a new hectad record for the locally rare Agrostis vinealis (brown bent) and Carex binervis (green-ribbed sedge), found at Foxhills.

The highlight of 2018 for me has been the volume of data going into the BSBI database, over 29,000 records. That is about 3,000 more than any previous year in the Atlas 2020 recording period, so as we enter the final year of recording it is great that we are sustaining and building upon the momentum of the last few seasons. Around 5,000 records came from Thames Valley Environmental Records Centre via our data sharing agreement, and Tim Harrison sent me an amazing 6,000 from SU79 and other parts of the Oxfordshire Chilterns. There were also solid contributions from outings led by Sally Abbey and Frances Watkins, and big individual contributions from Roger Heath-Brown, Frank Hunt and Clare Malonelee. I am very grateful for the efforts of everybody who sent me records in 2018.

If you would like to see the difference your contribution has made this last or any previous year, I have updated my Atlas progress map. In addition to showing the tetrad coverage, records and recording rate, you can now also see the equivalent for hectads, and compare the current recording period (2000-2019) with the recording period for the New Atlas (1987-1999). The squares now also link to hectad lists as well as tetrad lists, useful for identifying taxa that are still needing to be found for the current Atlas. Apologies if you don't like the grey colour scheme - if you can suggest an improvement then I will change it!

Finally, the Atlas is not just about going out recording and finding nice things but also about getting the data into shape for publication. I am sure you will be fascinated to know that this year I have managed to make substantial progress with checking the BSBI's data holding for the county, having looked at over 270,000 records. This has created further work, having identified about 1,000 records that need following up. Of course the best way to check records is to do so at the point at which they are sent me by the recorder - I am very grateful for recorders' help in resolving my queries about their records. This can be quite time consuming, so when you are out recording please do remember that any extra information you can provide with a record, especially status, accurate grid references and notes, helps with the verification process.

Looking forward, there's plenty to be excited about this year, not least the final year of Atlas recording. For instance, on Saturday 9th March the Oxfordshire Flora Group (OFG) is hosting a conference at the Centre for Ecology and Hydrology in Wallingford on the topic of 'The Dynamics of the Oxfordshire Flora' - a programme for the conference can be found on the OFG website. There will of course be plenty of field meetings this year, and I have added a provisional programme to the events calendar. I hope to see you at some of these or other events this year!