Saturday, 3 December 2016

Recording highlights from 2016

As the miserable weather settles on us and we enter the season of armchair botanising (at least for higher plants), I offer my reflections on what has been a very rewarding season. These highlights are based on exciting plants I've seen this year and range from new county records and new sites for county rare plants, to re-finds of plants thought potentially extinct in the county. I can think of many further delights I'd have liked to have included, but at least that leaves plenty of material for other posts. Do let me know if there's anything you'd like to share.

 A star re-find


For me the star find of the season is Rosa agrestis (small-leaved sweet briar) a nationally scarce rose and specialist of limestone grassland, mostly chalk in southern England. It has not been seen in the county for decades, but, while a rare plant, as a persistent woody species it has almost certainly been overlooked.


We owe this excellent record to visiting botanists Paul Stanley and Eric Clement who found several bushes at Pyrton Hill in September at the scrubby edge of the downland there. Remarkably, it hasn't been seen at Pyrton since Druce saw it in 1897, and not in the county since 1979 at Wendlebury Meads (SP5617). There are several more records of R. agrestis from around the latter area but I've yet to relocate it. Paul provided me with excellent directions to the plants - if you would like to go find them at Pyrton Hill them I am happy to provide further details. Needless to say, I was over there like a shot to pay homage to the only native rose I'd not seen.

Right: Rosa agrestis is the only sweet-briar without glands on the pedicels. The glands on the leaves can be seen clearly in this excellent image by Gareth Knass from the south of France. It is the only UK rose species with wedge-shaped (as opposed to rounded) bases to the leaflets.

New sites for county rare plants



Carex pulicaris. Source: Wikimedia Commons
Woodsides Meadows, a field owned by BBOWT within the Wendleybury Meads and Mansmoor Closes SSSI just to the north-west of Charlton-on-Otmoor, received a lot of attention from me this year. It's a truly flabbergasting place, and although it's been well-botanised over the years the meadow turned up a few things not previously recorded from there. The most notable were the small sedges Carex pulicaris (flea sedge) and C. hostiana (tawny sedge) - the former is known in V.C. 23 from few other sites, all old meadows, including Otmoor. These two sedges are characteristic of fens and related grassland communities which are now very rare in Oxfordshire being mostly seen in the remaining meadows of the river Ray catchment.
I also found Potentilla x mixta, the hybrid between P. reptans and P. anglica. This is a not uncommon plant in parts of the country, but there are very few records in Oxfordshire (7 records, the only recent being in 2010) - perhaps some of our P. anglica records represent misidentifications for this hybrid (17 records), or it could be mistaken for odd P. reptans.

Right: The salient features of Potentilla x mixta. Source: Whiteknights Biodiversity

A field pond in the meadow adjacent to Woodsides also supported a few tussocks of Juncus compressus (round-fruited rush), a new site for this uncommon rush. A scrape in the Flood Field in the northern part of RSPB Otmoor was also a new site this year. Otmoor has  received much attention this year, both the SSSI and RSPB reserve being the focus of field meetings organised by the Oxfordshire Flora Group. The long list of county rare plants during these meetings does great credit to the restoration work of the RSPB over the last twenty years and the management of the SSSI by the MoD and their tenants.

Many of the rarities found this year at Otmoor have been recorded in the recent past, but some were new, notably Alopecurus aequalis (orange foxtail) and Schoenoplectus tabernaemontani (grey clubrush) from scrapes within the RSPB reserve. Botanising the SSSI also turned up the first record of Spirodella polyrhiza (greater duckweed) from Otmoor for some decades, and we found that experimentally introduced plants of the Otmoor speciality Viola persicifolia (fen violet) were well-established and even spreading in a corner of the RSPB reserve.

Right: The Anglo-Saxon pond at Otmoor SSSI known as Fowl's Pill is the only Oxfordshire locality for Apium inundatum. Further rare species are found in the Pill but are now known also from the neighbouring RSPB reserve, e.g. Baldellia ranunculoides.

One final exciting rare plant, and one I found almost on my doorstep in a rapeseed field in Islip, is  Scandix pecten-veneris (shepherd's needle). This is only the fourth record of this critically endangered species in V.C. 23 this century; it is also the first record in the 10km square SP51. It was growing in some quantity along the Oxfordshire Way from Noke into Islip (SP 5368 1323) and there were a few more along the field margin. 

Right: The unmistakable Scandix pecten-veneris growing in an unprepossessing rapefield. These photographs of flowering/fruiting plants were taken on 19th January - maybe worth a look for my New Year Plant Hunt this January!

Aliens


A few aliens have been added to our flora over the last year or so, mostly casual escapes from gardens. However, two of the non-native additions from this year that I'm aware of are rather more interesting.

Dittrichia graveolens (stinking fleabane) is a short, shrubby fleabane-like member of the daisy family (Asteraceae) with which perhaps many will not be familiar (I wasn't). It is a southern European species with some determination: it has been marching northwards out of Southampton for several years and has made it as far as Greater London along the M3 (via every tetrad!). Its advance along the A34 seems to have been much more modest and it stops short at Hants/Berks border south of Newbury. However, this year I've been seeing it all over the place, including V.C. 23, where I saw some along the central reservation of the A34 near the Peartree interchange (SP4956611276). As you might have guessed it is readily identified at 70mph - in fact, I have yet to actually see the plant except through my driver-side window!

I received word from Matthew Berry (the BSBI aliens referee) that D. graveolens has been seen before in Oxfordshire but the records have not been submitted. I have no details, but perhaps this means its presence in the county could be much more extensive. Please keep an eye open for it on big roads! There are a few other plants found along our major roads whose frequency in the county is not, I think, reflected in the available records - a subject for a future post!

Left: Dittrichia graveolens is characteristically pyramidal in shape, and its small yellow flowers (inset) appear in September and ripen prolific fruit with a feathery pappus. Source: Wikimedia Commons

The second non-native addition to the flora is a shield fern, Polystichum tsus-simense, a widely sold hardy Asian fern. We're used to non-native seed plants but non-native ferns are really quite unusual in the British flora. Only six records of plants established in the wild have been made, all in cities in southern England (Bath, London and Winchester), all recent (since 2008) and all in walls. The specimen I found was along the wooded bank of the Lye Valley Brook in Headington, Oxford (SP50). With milder winters perhaps P. tsus-simense might be on the increase?

I confess that I didn't identify this plant myself, but then it isn't in any of the books. However, I at least realised it was a bit weird and wisely showed it to Fred Rumsey, a fern referee for the BSBI, and he identified it as P. tsus-simense. It is quite different to our native Polystichum species: the frond shape is pretty much triangular, the lowest pair of pinnae being about as long as those mid-frond; its pinnules (the smaller 'leaves' of the frond) are a little like P. setiferum, making an angle of ninety degrees or more at the base, have quite long teeth (though perhaps less regular) and have a conspicuous stalk to them; however, the frond is quite glossy in texture like P. aculeatum.

Right: Polystichum tsus-simense, new to V.C. 23. Thanks to Fred Rumsey of the Natural History Museum for sending me this scan of the plant I found along the Lye Valley Brook, Oxford.

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