Oxfordshire: Chiltern Escarpment: Aston Rowant to Oakley Hill

21 August 2012                       OS Explorer 171: Chiltern Hills West

Length: All day.

We parked at Cowleaze Wood SU725955.  We walked to the north end of this Beech Fagus sylvatica wood on rather acid clays dominated by Tufted Hair-grass Deschampsia cespitosa and crossed the road to the path that enters the Bald Hill section of Aston Rowant National Nature Reserve.  This reserve covers the best of the Chiltern chalk escarpment grasslands and we would spend the whole morning exploring much of it before we engaged in any extensive walking, as there is so much to look for here.  At the entrance from the road a handy leaflet with a map is available and we initially took the northern arm of what is labelled there as “Sheepcote Lane Walk” (orange) to the circular “Linky Down Walk” (blue dots), going NE then NW.

Map of Aston Rowant NNR showing trails

(from Natural England leaflet)

This first crossed a plateau meadow, still on the clay, with Corn Mint Mentha arvensis, Hop Trefoil Trifolium campestre, Wild Basil Clinopodium vulgare, Red Bartsia Odontites vernus, Common Centaury Centaurium erythraea, and Lady’s Bedstraw Galium verum. 

Corn mint – popular with flies

Wild basil

We then walked through a sheep pasture where the grass was shorter and less floriferous, although we did see Harebell Campanula rotundifolia.  After this the trail turns left to descend the hill on the chalk. 

Instead of following the trail down through a double hedgerow we entered an open gate leading to the steep SW-facing slope where we could see scattered stands of Juniper Juniperus communis. 

Juniper on Bald Hill

On southern chalk down-lands juniper is endangered because it rarely seems to regenerate naturally, leaving an increasingly ageing stock.  There are some fenced enclosures to prevent grazing of young juniper and in one of these we noticed a small plant that looked healthy enough as a contribution to a new generation.  The rest of the slope is winter-grazed to keep the grass short and encourage the rare turf flora.  The flowers in turn attract a large range of butterflies and these were evident even though the day was overcast, with Meadow Brown, Small Heath, Common and Holly Blue, Red Admiral and Brimstone.

Common blue on wild basil

 The flowers here included the usual Small Scabious Scabiosa columbaria, Marjoram Origanum vulgare, Fairy Flax Linum catharticum, Dwarf Thistle Cirsium acaule, Musk Thistle Carduus nutans, Burnet-saxifrage Pimpinella saxifraga, Salad Burnet Sanguisorba minor (some of the leaves covered in the white cottony galls of the mite Aceria sanguisorbae), Common Eyebright Euphrasia nemorosa, and Quaking-grass Briza media, but also plenty of newly-emerged Autumn Gentian Gentianella amarella, the last remaining flowers of Rock-rose Helianthemum nummularium, Yellowwort Blackstonia perfoliata, Carline Thistle Carlina vulgaris, and, on the barer ant-hills, Wild Thyme Thymus polytrichus and Squinancywort Asperula cynanchica. 

Dwarf thistles

Autumn gentian

Squinancywort

Among the harebells were a few completely white specimens. 

White harebell

Additional butterflies here were Brown Argus and several of the rare Silver-spotted Skipper.

Silver-spotted Skipper on Small Scabious

Near the bottom of this section, which we followed NW parallel to the trail, we found another gate to regain the latter.  Here we added Blue Fleabane Acer erigeron to our list.  The track descended through another floriferous long-grass meadow along the edge of the reserve to Hill Farm and the beginning of a paved road.  100 metres along this road we met the Lower Icknield Way (Ridgeway) and took this track to the right, with flocks of goldfinch flitting between the bordering hedges.  Along here the blue fleabane was abundant, there were patches of Meadow Cranesbill Geranium pratense in seed, and in the shadier areas Sanicle Sanicula europaea.

Blue fleabane

 Our most venerable track leads incongruously under the ultra-modern M40 Motorway which divides the reserve into two and restricts movement of creatures, like the less vigorously flying butterflies, along the down-land.  It also turned what should be beautiful quiet pastoral environment into one where we could not escape the constant loud drone of speeding traffic.  The cutting of this route through the centre of one of our best nature reserves and one of the most scenic parts of the Chilterns Area of Outstanding Natural Beauty must be one of the greatest of environmental crimes ever committed by the British government.  To see this white gash through all this made our hearts grieve and confirmed opposition to the HS2 high-speed railway scheme planned to cut yet another gash through a beautiful part of the Chilterns further east.

M40 crossing Ridgeway

After the motorway we came to a track on the right leading up into the Beacon Hill section of Aston Rowant reserve, but we first went on a short distance to examine the narrow wood on the left-hand side of the Rigeway, Lewknor Copse.  Here Spurge-laurels Daphne laureola were everywhere with their evergreen leaves, although they had dropped their berries, and abundant woodruff Galium odoratum. 

Spurge laurel

Despite the wet summer the ground here was very dry and the spurge-laurels seemed to be suffering except where the shade was deepest.  We also found one clump of narrow-lipped orchids Epipactis leptochila here.  They had just finished flowering but the dried petals on the tip of the lowest developing seed-pod still showed the narrow central lip after which it is named.

Narrow-lipped helleborine in seed

After examining this copse we returned to take the path up into the reserve again.  This led to a steep slope of short grassland with abundant Clustered Bellflower Campanula glomerata, which we followed to our left. 

Botanically rich grassland, Beacon Hill, with clustered bellflower

At the top of this near the path and wherever there were bare disturbed patches the increasingly rare Pale Toadflax Linaria repens was abundant: it was good to see it doing so well. 

Pale toadflax

Other plants of the bare chalk scrapes were Wild Mignonette Reseda lutea and Wild Candytuft Iberis amara, the latter unfortunately now only in seed. 

Wild mignonette with Wild candytuft seedheads

We also saw Dropwort Filipendula vulgaris, now in seed, and some Yellow Rattle Rhinanthus minor.  Clustered bellflower continued common along here among more autumn gentian, rock-rose and squinancy-wort.  Scattered junipers looked wind-swept and age-worn. 

Old juniper, Beacon Hill

In a patch of scrub we glimpsed a Dark Bush-cricket which turned out to be camera-shy.  Equally shy was a Mistle Thrush we frightened up from among the Hawthorn Crataegus monogyna bushes.  By the path skirting the hill-top we saw Ploughman’s Spikenard Inula conyza.  We eventually came across a minor path going to the peak of the hill, on which we came across another decreasing plant, Frog Orchid Dactylorhiza viridis.  These were again in seed, having been at their best about a fortnight earlier. 

Frog orchid

Nearby was a white specimen of autumn gentian.

White autumn gentian

From the top we continued along a track going SE along the side of Beacon Hill to the reserve car park.  This passes through an octagonal concreted area where there used to be a visitor centre.  Here were some seats overlooking the view where we ate a quick lunch, the motorway partly shielded by trees planted below but, if out of view, certainly not out of earshot. 

M40 from Beacon Hill

The pretty yellow-and-black hoverfly Xanthogramma pedissequum was keen on the nectar of Wild Carrot Daucus carota at our feet.

Hoverfly Xanthogramma pedissequum

From the car park we walked the minor roads to the A40.  The woods here were full of Wood Barley Hordelymus europaeus, with some Wood Melick Melica uniflora on roadside banks.  Just out of the woods, where we joined the Cowleaze Wood road, was a huge sarsen stone, presumably left after weathering of the clays around it, as it seemed much too large to have been shifted. 

Large sarsen

We proceeded NE to the A40 road, where there was a large patch of meadow cranesbill at the corner.  We crossed and continued on the minor road, past some Hedgerow Cranesbill Geranium pyrenaicum, until it bent sharply left and we continued straight on by means of a bridleway.  Kingston Wood on the left again had abundant wood barley.

          The bridleway bends right, keeping to the edge of the wood, and after half a kilometre we took a footpath angled back left to regain our original direction through Kingston Wood.  Although this is legally a “footpath”, it is heavily used by horses and cycles, as it connects two bridleways.  No attempt ever seems to be made to police these paths and prevent such inappropriate use.  The woods along this path are quite moist and contain some large ferns, including not only the common Male and Broad Buckler Ferns Dryopteris filix-mas and D. dilatata, but also some much rarer in the eastern half of the country, Borrer’s Male Fern Dryopteris borreri, with shaggier mid-ribs to the fronds and a black patch at the base of each pinna, and Lady Fern Athyrium filix-femina. 

Borrer’s male fern

Lady fern

As we continued through the beeches of Crowellhill Wood we passed one splendid spike of Violet Helleborine Epipactis purpurata sheltering under a holly bush Ilex aquifolium. 

Crowellhill Wood

Violet helleborine

It may have been this slight protection that prevented it becoming a bitten-off stem like all the other specimens we found, the victims of over-numerous deer (muntjac, roe) in these woods.  We also noted some Tutsan Hypericum androsaemum.

          Eventually we reached then end of the road at Crowell Hill and took the bridleway descending the scarp again through Crowelhill Wood, where the vegetation was sparse and dominated by Giant Fescue Festuca gigantea and False Brome Brachypodium sylvaticum.  At the end of the wood we made our way through a rough field with yellow-wort and common centaury to reach the Ridgeway again.  At this corner there was a gate into Oakley Hill Nature Reserve (Berks, Bucks and Oxon Wildlife Trust).  Above a tall grass meadow with lots of Common Blue Damselflies, we came to a grazed slope with a mixture of short and long grass. 

Common blue damselfly

An immediate contrast with the grasslands we had traversed at Aston Rowant in the morning was an abundance of Chiltern Gentian Gentianella germanica instead of autumn gentian.  There did not seem to be the mixture of the two species as often occurs.  The Chiltern gentians stood out by reason not only of their larger growth and widening calyx but also the dark, purplish leaves and deeper purple flowers. 

Chiltern gentian

Many of the chalk flowers we had recorded at Aston Rowant grew here as well, especially lots of clustered bellflower, small scabious, carline thistle, and blue fleabane.

Carline thistle

There was also common eyebright, although here the latter was mixed with larger-flowered Chalkhill Eyebright Euphrasia pseudokerneri, although both were variable in flower-size and there seemed to be many intermediates. 

Chalkhill eyebright

The chalkhill eyebright was best identified by the long bristle-like tips to the teeth of the flower-bracts, coupled with at least some larger flowers (there were often smaller ones on the same plants).  “Pure” Euphrasia nemorosa actually seemed to be relatively infrequent.  There was also Large Thyme Thymus pulegioides here, having so far seen only wild thyme at Aston Rowant.

          We were surprised to see a large distinct patch of purple grass which looked like Wood Small-reed Calamagrostis epigejos and turned out to be so, despite being in open grassland instead of the familiar woodland habitat.  Apparently this grass has in recent decades started to appear in such open situations.  Here it looked as though it had the capacity to be quite invasive and dominating, although of course sheep grazing, used by the Trust over the winter, would prevent it spreading.

Oakley Hill reserve, with purple wood small-reed patch at right

We added Small Copper and Gatekeeper to our butterfly list and a pure white clustered bellflower to our “albino” list for the day. 

 

Below the reserve lie the Chinnor chalk quarries, their blue waters inhabited by tufted duck, coots and Canada geese.

Chinnor chalk quarry

This reserve was the furthest point NE we intended to reach today and we returned to the Ridgeway for an easy and straight walk back to the vicinity of Aston Rowant.  Although the vegetation along here was not remarkable, we did see some tutsan, Alsike Clover Trifolium hybridum, and Wormwood Artemisia absinthium, the latter conveniently near its relative Mugwort Artemisia vulgaris for its greyer less sharply lobed leaves to be readily discernible – its strong smell bringing immediate confirmation.

Wormwood leaves

When we reached the point near Hill Farm where we first came down to the Ridgeway we continued for another half a kilometre to the footpath on our left that goes south across a field and then a wood before turning abruptly SE along the outside of the wood (some Long-stalked Cranesbill Geranium columbinum and Field Madder Sherardia arvensis in the grazed grassland here) and going uphill to Bald Hill, this time along the bottom of its SW-facing slope.  Here in the nature reserve once more was a huge population of Chiltern gentian, whereas we had seen only autumn gentian north of the hill. 

Chiltern gentian on Bald Hill

There Autumn gentian was accompanied by wild thyme, as against the large thyme that seemed to be most frequent here.  Here was also some Rest-harrow Ononis repens.  A bare-topped anthill at last revealed, among some large thyme, a few spikes of the rare Mat-grass Fescue Vulpia unilateralis, which we had been seeking all day, having seen it in the reserve five years before.  Now, later in the year (it flowers May-June), it was reduced to tiny dry yellow stalks, but its one-sided small flower-spikes were still identifiable.  We climbed up the steep slope through dense gentians and other flowers, including more chalkhill eyebright, frog orchids, and a small Common Spotted Orchid Dactylorhiza fuchsii still visible in seed.  A caterpillar feeding on hairy rosette leaves of what may have been devilsbit scabious (although we saw no flowers of this plant) was the club-horned sawfly Abia sericea. 

Larva of club-horned sawfly

By then we could see the rain that had threatened all day coming from the south along the escarpment and it caught us as we reached the top of the hill and regained the path to Cowleaze Wood, arriving back at the car wet-through, but pleased with the day’s discoveries and relieved that the storm had not struck much earlier, as a favourable weather forecast had lured us into venturing out without wet gear!

Oxfordshire: Oxford Centre & Port Meadow

223 July 2012
Length: All day                A good town centre map is adequate for this walk

We began in the High Street, going south along the narrow lanes going to the old roads of Blue Boar Street, Bear Lane and Merton Street.  The old college walls along these were explored in our walk of 12 April and most of the species recorded then were still evident.  In addition to that list we saw Oxford ragwort Senecio squalidus, polypody Polypodium vulgare, maidenhair spleenwort Asplenium trichomanes, red valerian Centranthus ruber, Canadian fleabane Conyza canadensis, bristly oxtongue Picris echioides, nipplewort Lapsana communis, buckshorn plantain Plantago coronopus and Welsh poppy Meconopsis cambrica.  A hawkweed was also frequent, with sticky glandular hairs and few stem-leaves, which we identified as Hieracium amplexicaule or “sticky hawkweed”. 

Hieracium amplexicaule

Leaf-mines on many of these were caused by the agromyzid fly Chromatomyia atricornis (actually a combination of two species that are difficult to separate).  At the base of some walls there was also fern-grass Catapodium rigidum and ratstail fescue Vulpia myuros. 

Fern-grass

The pavements were also enlivened by the miniature exotic “palm-trees” of common liverwort Marchantia polymorpha ssp ruderalis.

Common liverwort

We returned to the High Street and went east to the Botanic Garden.  Opposite Magdalen College, Rose Lane travels along the side of the gardens.  The Hieracium scotostictum (leaves dark-splodged like maculatum but with no or only one stem-leaf) that we had seen here only in leaf before was now in flower and seed, while the rue-leaved saxifrage was very brown indeed.  They were now joined by purple toadflax Linaria purpurea and, on the wall-top, by flattened meadow-grass Poa compressa.

          We then revisited the gardens, which always have something of interest throughout the year, and not always deliberately planted. 

Oxford Botanic Garden

We noticed the Mediterranean rue Ruta graveolens was a popular nectaring plant among the bees, and might be a good addition to a garden, although if touched in sunlight it is prone to cause blisters.  Nearby a small tree of Sargent’s rowan Sorbus sargentiana contained a large bunch of berried mistletoe Viscum album unusually at eye-level, very convenient for a closer look than one can usually get. 

Mistletoe on Sargent’s rowan

We revisited the true service tree mentioned in our April blog and now it was fruiting quite prolifically, although these fruits, like miniature pears (hence its other name of “Whitty pear”), were as yet still green. 

True service with green fruit

It was also now in leaf so that one could see the great similarity to our native rowan, which makes the tree difficult to spot in the wild if (as is usually the case) it is not fruiting.

True service leaves

Two exotic broomrapes have been recorded from the gardens, one parasitic on barberry and the other on butterbur (see the “Flora of Oxfordshire” by John Killick, Roy Perry and Stan Woodell), but we could not find either of those host plants growing there today.  There was plenty of ivy broomrape Orobanche hederae.

Ivy broomrape

There were also a few intriguing spikes of broomrape on a plant of sea-holly Eryngium maritimum, which seemed to match those of the distinct yellowish variety of common broomrape Orobanche minor that is found on the same plant at Sandwich Bay in Kent (which has in the past been wrongly identified with the Mediterranean Orobanche amethystea, a parasite of Eryngium species!). 

Broomrape on sea holly

It is possible that the gardens obtained their plants of sea-holly from Kent and thus unwittingly introduced the broomrape with them, although some argue that common broomrape assumes different forms according to its host, whose chemical make-up may affect colouring and form of its parasites.  Ivy broomrape has itself often been considered as just a form of common broomrape rather than a separate species.

          A less welcome accident in the gardens is small balsam Impatiens parviflora, plants of which were noticeable in many different beds.  Its explosive seed-pods make it good at spreading itself and once present is difficult to eradicate.  We have noticed that it is an increasing problem in many native woodlands.

          On our last exploration of Oxford in April we looked unsuccessfully for ladder brake Pteris vittata on the outside walls of the greenhouses.  This time we did find a very young specimen among the maidenhair fern Adiantum capillus-veneris on one of the walls. 

Ladder brake on greenhouse wall

Nearby was a lot of mind-your-own-business and, in the cultivated borders, a delicate lilac sorrel with distinctive narrowly-bilobed leaflets was coming up everywhere.  We identified this later as Oxalis livida, using the useful Pacific Bulb Society website.  It comes from South Africa.

Mind-your-own-business on greenhouse wall

Oxalis livida

The River Cherwell comes close to the greenhouses and on the stone banks sticky hawkweed was again in evidence.  There was also much hawkweed on the garden walls, but too high to reach to identify, but certainly Hieracium amplexicaule has been recorded from those walls.

Sticky hawkweed by the Cherwell (with maidenhair spleenwort)

As usual we could not resist another look inside the glasshouses to see what was in flower.  This included an epiphytic orchid Encyclia fragrans from Brazil, apparently the most abundant orchid in the central Amazon. 

Encyclia fragrans

Even more impressive, however, were the hanging bunches of the incredible turquoise flowers of the jade vine Strongylodon macrobotrys from the Phillipines.  The garden’s website was excited about the flowering of this vine, which it does not do every year.  The vine stretches across the whole roof of the Lily House and it is difficult to believe the flower spikes are not artificial plastic ones, so unusual is the colour in nature.

Jade vine

We finally visited the tropical pool with various water-plants, like the spectacular Victoria lily and Nymphaea mexicana water-lilies.

Tropical water-plants

Leaving the garden we backtracked a little to go north on Longwall Street by the side of Magdalen College.  Although this street is indeed bordered by a long wall, the latter is immaculately cleaned and bears no plants at all.  However, it is the direct route to StCross Church, where the old lower churchyard is maintained by volunteers as a wildflower reserve.  We found them there today repairing a wall at the bottom.  There are meadow and hedgerow cranesbills Geranium pratense and G. pyrenaicum to be found here, yellow rattle Rhinanthus minor, and, at the far SE corner, several large clumps of deadly nightshade Atropa belladonna, perhaps appropriate to a graveyard. 

Meadow cranesbill, StCross Cemetery

Deadly nightshade, StCross Cemetery

The flowery long grass attracted many butterflies.  By the entrance gate (which is just before the new cemetery) we found creeping bellflower Campanula rapunculoides, a garden escape.

          We retraced our steps a short way to Holywell Street going off to the west.  We followed this across Parks Road, which at one time was noted for such an abundance of escaped Inchnadamph rampion Phyteuma scheuchzeri on its walls that it gained the local name of “Oxford rampion”.  Unfortunately a session of over-exuberant wall-cleaning in 1993 completely wiped out the colony.  A single plant had also been seen near the Martyr’s Memorial at St Giles, to which we eventually came, but, not unsurprisingly, this was no longer to be found.  From here we continued west along Beaumont Street.  The Ashmolean Museum along here has a rooftop restaurant and provided a respite for lunch on a very warm day.

          Continuing along Beaumont Street to the end we turned south and then west along Hythe Bridge Street.  This crosses both the Oxford Canal and a branch of the Thames, and a footpath descends to the towpath along the narrow length of land separating the two.  Near the bridge were common skullcap Scutellaria galericulata and gypsywort Lycopus europaeus growing on walls beside the water.  Banks of the river had the expected plants like meadowsweet Filipendula ulmaria, purple loosestrife Lythrum salicaria, water dock Rumex hydrolapathum, water figwort Scrophularia auriculata and hemp agrimony Eupatorium cannabinum, but the path side soon became dominated by the miniature gardens that always seem to be planted where barges moor. 

Barge moorings

The vegetation then became dominated by garden plants like the hybrid Druce’s cranesbill Geranium x oxonianum (whose specific name apparently refers to Oxford) and its parents, pencilled and French cranesbill G. endressii and G. versicolor, along with that increasingly frequent escape fox and cubs Pilosella aurantiaca, and native wall barley Hordeum murinum.   

Pencilled cranesbill

House holly-fern Cyrtonium falcatum was also established, although it could hardly be judged as really wild.  A bridge at Isis Lock had rustyback fern Ceterach officinarum growing on it in plenty.  In the water here we saw the conspicuous red fins of roach Rutilus rutilus.

          We left the path at the Walton Well Road bridge and took the road west over the railway line, after which we took a footpath on the right going north between a stream and the railway, passing common valerian Valeriana officinalis, water-plantain Alisma plantago-aquatica and false fox-sedge Carex otrubae.  This path eventually runs into a track running west into Port Meadow.  On steps going up to this track we saw knotted hedge-parsley Torilis nodosa, a scarce plant in Oxfordshire.  As we entered Port Meadow, common land divided among many owners in the old tradition, the ground became very marshy.  Tubular water-dropwort Oenanthe fistulosa was everywhere, despite having become generally uncommon with the disappearance of most of the old water-meadows. 

Tubular water-dropwort

Its frequency may have been enhanced this year by the persistent rain from April to late July, which had made Port Meadow much damper than usual.  In fact a large area was still flooded around the very low prominence known as Round Hill, as it would be generally only in the winter months. 

Port Meadow flooded

This frustrated our plans to search for the very rare creeping marshwort Apium repens at its only remaining site, as we remembered having found it close to Round Hill in damp hollows, now under a foot of water.  We hope that this summer inundation does not damage its chances of survival – perhaps it may even help it spread by making the meadow wetter, despite the fact that this year it will have had no chance to flower and seed.  It has to be carefully distinguished from dwarf forms of fool’s watercress Apium nodiflorum, which is common here, by observing the rarer plant’s multiple lower bracts, longer stalks to the flower-heads, broader fruits and rooting at every node.

Creeping marshwort taken in a previous year

(we were hoping to get a better picture this time!)

While we could not search for the marshwort, we could at least observe large flocks of little egrets, grey-lag geese and black-headed gulls enjoying the water and obviously finding plenty on which to feed.  Also abundant were dragonflies, particularly black-tailed skimmers. 

Black-tailed skimmer

As far as we could search the very marshy ground we did find celery-leaved buttercup Ranunculus sceleratus, water forgetmenotMyosotis scorpioides, creeping yellow-cress Rorippa sylvestris and amphibious bistort Persicaria amphibia.

Creeping yellow-cress

Amphibious bistort

We had to abandon our plans to search the Meadow further and returned to the south end and the bridge over the Thames or Isis that runs along the meadow’s west side (chicory Cichorium intybus growing here) and walk north along the bank to Godstow.  It was pleasing to see a great crested grebe here, but the path-sides and the river banks are heavily grazed and used by people, so there were no interesting plants along the way.

Barges in Thames and flooded Port Meadow beyond

Thames near Godstow

This made it a tedious mile and a quarter to get to the ruins of the old nunnery at Godstow.  The target plant here was birthwort Aristolochia clematitis, a medicinal plant grown by the nuns, who presumably, going by its name, acted as midwives for surrounding villages.  The plant survived here in good numbers from medieval times until at least the 1990s, when we found it in plenty in 1994 along a ditch travelling west from the nunnery.  Unfortunately this area is now heavily grazed and the site where we had seen the plant was overgrown with shrubs.  We could not find a single specimen, a sad reflection of our times when such rarities can be so neglected and allowed to disappear in just a few years after centuries of survival.  This made the walk back even more tedious!  There is now little point in making the trek to Godstow (the remains of the nunnery in themselves being very plain) and the walk can best be finished at Port Meadow, from where there are many ways back east over the canal to Oxford.