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