Invasion of the False Natives

Lookalikes (species similar to and planted in mistake for native species) and false natives (infraspecific taxa of foreign origin) have slowly been growing in profile over recent years following Peter Sell bringing these to a wider audience, and then the inclusion of a number of such plants in Edition 3 of Clive Stace's New Flora of the British Isles. But there is still some way to go in understanding the true distribution of these taxa, and the long term implications of 30 years zealous tree and shrub planting as quick fix habitat mitigation and creation.

Southern Dogwood (Cornus australis or Cornus sanguinea subsp. australis) is one good case in point, with the following map showing a rash of dots across central England. This species is almost ubiquitous in recent plantings in VC31, and is increasingly being found bird sown. A similar picture is building in VC64. My personal view is that this isn't a trivial matter. Southern Dogwood seems to grow more vigorously and forms a much denser bush, so I can see it being a problem for habitat managers in the future. It is obvious why horticulturists have favoured it as it has larger flowers and leaves than the native plant, produces a neater denser bush and has brilliant autumn colour.



The characters used in keys to distinguish it from Dogwood (Cornus sanguinea) are subtle and based on the number of leaf veins and the morphology of leaf hairs, but this belies the genuine differences between the two species. The leaf hair differences, visible with a hand lens, are well illustrated on the Manual of the Alien Plants of Belgium website. Once known the two species can usually be told at a glance with very high accuracy, but it always advisable to check the hairs. More recorders need to be looking for and distinguishing the two species if we are to have a representative picture of their true range in time for the next Atlas.

The typical large and rounded foliage of Southern Dogwood

The hybrid hawthorn Crataegus x subsphaerica is the subject of a separate post which can be found here. But I just wanted to show the current map of is distribution in VC63 and 64 following targeted searches this autumn. Note the two new locations well to the north of the Leeds cluster. It will be interesting to see how many new dots are added in 2017, I suspect it is going to prove very widespread and abundant.

What is interesting about my find at Moor Monkton (VC64) is that the original planted trees appear to have produced new trees much closer to Hawthorn (Crataegus monogyna) than the original stock. This suggests backcrossing, and this will add to identification difficulties in the future. Similar backcrossed bushes were found bird sown at Knostrop where there is a hedgerow dominated by the hybrid and estimated to be 30 years old. Clearly the hybrid has been with us for a while and has had plenty of time for birds to spread it around, so hybrids could potentially turn up anywhere.

Where There's Muck - Part II

So the visits to sewage works have continued and, despite the lateness of the season, so have the nice finds. They really are fascinating sites and a lesson in the resilience of seeds. At one site there was a veritable fruit salad with the mandatory Fig (Ficus carica) and Tomato (Solanum lycopersicum) being joined by Cape Gooseberry (Physalis peruviana), Strawberry (Fragaria ananassa) and even a well established Grape Vine (Vitis vinifera).

Life behind bars! - Fig tree making its way into the light(?) of autumnal Dewsbury (VC63)

This one has really got its roots down, that's one happy Fig - Knostrop (VC64)

Cape Gooseberry at Harrogate (VC64) - where else, Tomatos are so last year

Or how about this as an oddity, no idea what this says about the diet of people in Dewsbury!

Orange Bladder-senna (Colutea x media) - Dewsbury (VC63)

However, the best find for me of the last few weeks had to be the huge population (1000's) of Musk Stork's-bill (Erodium moschatum) at Knostrop (VC64). Nothing to do with the sewage treatment process, but it obviously liked the management regime at the site.

Photo by Dick Culbert from Wikimedia Commons

A Headache of Hawthorns

The 3rd Edition of Stace back in 2010 introduced Large-sepalled Hawthorn (Crataegus rhipidophylla) to British botanists, and encouraged me to start looking at hawthorns more closely. Away from ancient woodlands it was perhaps too easy to get blasé and expect Hawthorn (Crataegus monogyna) or its hybrid Crataegus x media. Sure enough, I first met with this species in Lincolnshire and I have found it in scattered locations thereafter. It is not common and, currently at least, is primarily of planted origin. However, it is undoubtedly under-recorded and other botanists should be looking more critically.

Large-sepalled Hawthorn stands out in the spring with its early and large flowers. The leaves are distinctive being redolent of Wild Service-tree (Sorbus torminalis) in outline with a saw-edged base to the leaf. In the autumn the large and typically barrel-shaped fruit appear and typically have erect sepals (depending on variety) that are longer than wide. What is also distinctive in the autumn is the early colour change and leaf drop, which starts in October well before Hawthorn and its kin.

Much more common than Large-sepalled Hawthorn is its offspring with Hawthorn i.e. Crataegus x subsphaerica. Indeed, having targeted this species this October I can say it is very common, undoubtedly overlooked and likely to be a real headache for botanists in the future. What has become most apparent to me over the last few weeks is just how variable this species is. In some guises it can easily be overlooked as Hawthorn or Crataegus x media when not in fruit. By the time the BSBI starts to think about the next Atlas (after the current 2020 project) it will likely be so ingrained in our countryside that we will become dependent on examination of fruit for definitive identifications.

When I first found C. x subsphaerica it was as the optimal form for ID i.e. hybrid vigour, leaves with the outline and toothing of Large-sepalled Hawthorn but the dissection of Hawthorn (forms with the influence of the heavily dissected monogyna f. schizophylla are particularly distinctive), and large fruit with erect sepals. However, all intermediates occur and now is a good time to look while leaves and fruits are still present. The leaves on different bushes can show every range of variation between the two parents. Leaves may have the saw-edge of Large-sepalled, or this can be reduced or vary from leaf to leaf, or can be absent entirely. The fruit size can vary from small to large. However, if there are erect sepals on the fruit (nothovar. domicensis) you can be confident of the ID. Note this character develops as the fruit mature, so don't make assumptions based on immature fruit.

This is the current distribution of the hybrid based on data in the BSBI database, and reflects where people are looking rather than the true distribution. It will only be the tip of the iceberg. My experiences around my local patch will undoubtedly be replicated across much of England and Wales, if not the UK as a whole.

Finally, to round off the hawthorns, a return visit to the fabulous large fruited (>1cm) form of Hawthorn (var. splendens). It is a stunning sight when you meet a bush of this in full fruit, dripping like jewels in a particularly vibrant shade of red. Despite the fact that this variety only occurs at very low density, i.e. one or two bushes here or there, it does seem more than a chance mutation. While the fruits of var. monogyna (and subsp. nordica if you follow Sell & Murrell, but the distinction betwen subspecies monogyna and nordica does not seem worth maintaining) and var. splendens do seem to vary in size on a single bush there does seem to be a well marked cut off in the size ranges between the two varieties. In other words, the fruit vary in size around their respective means, but do not grade into each other. A reasonable working hypothesis to explain this might be that the latter has a higher ploidy level.

Where There's Muck ...

Sewage Works are not the most glamorous of locations but they are always interesting places to visit (with work I should add - not my normal idea of a good day out!). This time of year is particularly good when all sorts of rarities pop up in composting and other marginal areas.

Yesterday rewarded me and my colleague Hannah with several plants of the stunning Apple-of-Peru (Nicandra physalodes var. violacea) at Esholt (VC64). The colour and size of the flowers never fail to impress and seem out of place on a grey autumn day.

We were also rewarded with a single plant of Cape-gooseberry (Physalis peruviana), unfortunately not in flower. Here are a couple of photos taken at Knostrop, Leeds (VC64) a couple of years back. It has also been seen recently elsewhere in the VC near Spofforth.

And to round off an interesting trip we found one plant of the hybrid between Oxford Ragwort and Sticky Groundsel (Senecio x subnebrodensis) growing with both parents. I was too excited to take a photo, but there is a reliable image here. This find nicely updates an old record for this area by Jesse Tregale.

Unwelcome Invader at Hemingford Grey (VC31)

Lynne Farrell found Floating Pennywort in the River Great Ouse at Hemingford today. This is a very invasive non-native species that will hopefully be eradicated before it has chance to establish. It would be very unfortunate if it got a foothold and then moved onto colonise the important gravel pit complexes along the river.

Floating Pennywort is a native of North America, but was introduced to Britain by the horticultural trade as an aquatic ornamental. As is too often the case with aquatics, it is a bit of a thug and once it starts to take over its not long before someone thinks it a good idea to turf it out into the nearest watercourse. Spread is somewhat inevitable after that, with this species capable of growing 20cm per day.

This species is well established at Bedford (VC30), so there is a high chance of it being washed downstream into Huntingdonshire. Please keep your eyes peeled, and if you see it report it via the Plant Tracker website or phone app, or by email to alert_nonnative@ceh.ac.uk.

For readers from Yorkshire, it is also depressingly frequent in the Rivers Don, Aire and Calder.

Marsh Dock

Wetland habitats still maintain some interest at this time of year, providing a 'last hurrah' before winter. St Aidan's (VC64) proved this last weekend with good numbers of Marsh Dock (Rumex palustris) still going strong. This is not a species I remember seeing here before, and it may be that I have missed it because it peaks late in the season.

This species has a primarily Eastern England distribution. It is widespread but scarce in Huntingdonshire, but is exceptionally scarce in VC64 where it seems to be restricted to wetlands along the Aire Valley. I wouldn't be surprised if it occurs elsewhere e.g. in the Ripon area, and it may be overlooked because of its phenology and also because many of the wetlands it favours have no public access or only restricted access to marginal habitats.

Slender Bulrush - New to VC64 and Beyond?

Slender Bulrush (Typha laxmannii) is widely established in the aquatics trade but doesn't seem yet to have been recorded as escaped in Britain. I'm sure that will change in the future. It turned up in a reservoir I was surveying in Skipton where it had clearly been bunged in, along with a range of other non-natives, by anglers. It seems to have been there for a few years and scattered stands around the margins indicate it is spreading and establishing at this site.

My eye was first caught by the very narrow leaves on a non-flowering clump and my first thought was Flowering-rush (Butomus umbellatus), only realising my mistake when spotting the flowers and looking closer at the leaves. It is closest in appearance to the native Lesser Bulrush (Typha angustifolia), but it is a dwarf in comparison. There may be situations where environmental conditions serve to dwarf Lesser Bulrush, but in my experience bulrush species are pretty resilient. Certainly the growing conditions at this site were very favourable for bulrushes, with this species growing at a depth of 0.7 to 1m (perhaps greater depth given I recorded it during the summer draw-down period).

Postscript: originally I stated this record was from VC63, however I was in error and it is well inside VC64. The joys of a county boundary based on the meanderings of a watercourse!

Recent Sightings (VC31)

So as not to leave Huntingdonshire out, here is a quick catch up on recent sightings.

Barry Dickerson had Caper Spurge (Euphorbia lathyris) pop up in his garden in Eynesbury. This species is only of scattered occurrence in the VC and is generally found close to habitation. This is one of my favourite plants, a combination of its alien looks and it being one of the first plants I noticed as a kid. The photo is by Barry.

Lynne Farrell and Barry have been out around Bluntisham and Lynne noted a new colony of Birthwort (Aristolochia clematitis) not far from the long known colony behind the Baptist Church. This species has persisted at this location since at least 1949, when it was first reported.

Photo by Bouba (Wikimedia Commons)

Lynne also found an old pear tree nearby that seems to be Wild Pear (Pyrus pyraster). At first the location seems a bit incongruous, but as this area used to be orchards it is possible that it was planted to serve as a pollinator for the fruit crop. Normally this species is found as an odd tree here and there on the edge of ancient woodland and in ancient hedgerows. Photo taken by Lynne after retrieval from the compost bin to double check a few measurements!

Recent Sightings (VC64)

A quick catch-up on recent news.

Mike Canaway has spotted Perennial Sunflower (Helianthus x laetiflorus) in rough grassland off Stackhouse Lane, Giggleswick. This is a striking but rare garden escape in VC64.

Photo by SB_Johnny from Wikimedia Commons

Jonathan Shanklin has paid the county another visit, for a week of intensive botanising in the Pateley Bridge area. His sightings include ...

New Zealand Hair-sedge (Carex comans) escaped on a road verge at Glasshouses (photo by Dinkum, Wikimedia Commons)

Small Toadflax (Chaenorhinum minus) at Pateley Bridge (photo by Stefan Lafnaer, Wikimedia Commons)

Caper Spurge (Euphorbia lathyris) at Middlesmoor (photo by JH Mora, Wikimedia Commons)

Wood Club-rush (Scirpus sylvaticus) at Ramsgill (photo by Christian Fischer, Wikimedia Commons)

Meanwhile, I have had the following:

Nodding Bur-marigold (Bidens cernua) at Eccup Reservoir

Phacelia (Phacelia tanacetifolia) as a casual in an arable field at Aberford, just what is needed to brighten an October day

Mudwort's Moment

Mudwort (Limosella aquatica) is very much the plant of the moment, having been found at a number of sites in VC64 and neighbouring VCs over recent days. So if you have a reservoir near you with public access then its worth a search.

It is not a common plant nationally - see the excellent BSBI Database which now has open access to the maps, and perhaps use it to identify historic locations for targeted searches. I am sure it must still be present at most of the larger upland lakes and reservoirs. Following on from the last blog it has now been found for the first time at Eccup Reservoir (two new tetrads and one new hectad), Scar House Reservoir (new hectad) and Scargill Reservoir (first hectad record for decades). Please bear in mind that not all these sites have public access, there are plenty more reservoirs with public access worth searching. I would also love it if it was found in Huntingdonshire, where there are plenty of old mineral workings. It is much less common in that part of Britain, but it is known from similar habitats at Titchwell (VC32) so its not impossible and there are a number of very old records.

Mudwort in typical habitat by Scar House Reservoir (photo by Hannah Mitchell)

Part of the reason for recent finds is focussed searching at a time of year when botanical recording activities are winding down. I have been lucky enough to be doing reservoir surveys recently and have been getting my colleagues to keep their eyes peeled also.

Other associated highlights include a new population, and a large one at that, of Small Water-pepper (Persicaria minor) at Eccup. This a major range extension. Like the plants in the reservoirs along the Washburn valley, the plants are all white flowered. Eccup also provided 1000's of plants, enough to be certain it was not just a chance aberration, of an unusual form of Red Goosefoot (Chenopodium rubrum). This goes by the name of var. pseudobotryoides and is readily distinguised because the plants form prostrate to decumbent mats with small leaves. The stems upturn at the end where they produce short inflorescences. Stupidly, I took no photos but there is a picture here. Not the best botanical illustration but it is excellent for showing the general jizz of this variety.

The Draw of Draw-down

Draw-down, the seasonal exposure of sediments around the margins of ponds, lakes and reservoirs over the summer, is a habitat I always like to explore whenever I have the opportunity. It is as appealing to me as arable field corners, as you never know what you might find, and there can be much of interest in late summer when other habitats are winding down.

I have been lucky enough to get around a fair few reservoirs in VC63, 64 and 65 in recent weeks and have found plenty of surprises and also, to be honest, a fair amount of not so much. Its the boring sites that make the other sites so much more rewarding. Here are a few of the highlights.

Mudwort (Limosella aquatica) at Scargill Reservoir courtesy of my colleague Hannah Mitchell, also present at Swinsty and Fewston Reservoirs

Musk (Mimulus moschatus) on the mudflats at the northern end of Fewston Reservoir

A rather poor photo that does not do justice to this delicate species - Small Water-pepper (Persicaria minor var. minor). The whole population at Swinsty and Fewston is the unusual white-flowered form. The more typical pink-flowered form was encountered later at Leighton Reservoir

Not as rare as the preceding species, but it is always nice to see Water-purslane (Lythrum portula subsp. portula). 

Intermediate Plantain (Plantago major subsp. intermedia), a drawdown specialist unlike its weedy cousin Greater Plantain (Plantago major subsp. major)

And that's just a taster without mentioning Shoreweed (Littorella uniflora), Sand Spurrey (Spergularia rubra), Marsh Speedwell (Veronica scutellata), Red Goosefoot (Chenopodium rubrum), Monkey-flower (Mimulus guttatus) ...

You've probably noticed the recurring theme in most photos by now - the menace that is New Zealand Pigmyweed (Crassula helmsii). Please take care to clean your boots so as not to help it spread any faster than it is already managing, otherwise you get this ....

Fewston Reservoir, that really is all New Zealand Pigmyweed and this is but one small part of the infested shoreline of this large reservoir

Kippax & Great Preston (VC64)

A couple of quick pics from this weekends stroll in search of Rosa x irregularis (found!).

I seemed to hit Townclose Hill (Billy Wood) just right this year for the Autumn Gentians (Gentianella amarella subsp. amarella). It was nice to catch them at peak bloom.

Back along The Lines I strayed into an adjacent arable field, I can't resist this habitat as there is always hope of finding a rarity. My luck was in and I was rewarded by a plant that was new to me, this being Niger (Guizotia abyssinica).

Coming back through Water Haigh Woodland Park in Woodlesford (VC63), I was also lucky to find a fine plant of Large-toothed Hawkweed (Hieracium prominentidens), which by the standards of the genus is a doddle to ID and one anyone should be able tackle with confidence. My photos were abysmal so check it out in Yorkshire Hawkweeds. If you don't own a copy yet, buy it while you can as it is written for those only just starting to dabble their toes into the wonderful world of Hawkweeds. A wonderful and well illustrated book.

Rosa x irregularis

I have been taking an interest in roses for a number of years now, a species group to be taken slowly and that rewards close observation, and have been gradually working my way toward trying to get to grips with some of the hybrids. Rosa x dumalis, in this case the cross between Dog-rose (Rosa canina) and Glaucous Northern Dog-rose (Rosa caesia ssp. vosaigaca), has been on my radar for a number of years, is very common and behaves like a species. In Huntingdonshire it is as common as Dog-rose, in VC64 it is also relatively common but as we are in Glaucous Northern Dog-rose territory it needs to be distinguished with care. But other than this one hybrid, I have only really dabbled.

Having come across an old paper where Chris Preston decribes his efforts to investigate and record the hybrids further, I thought it time I stretched myself a little and set myself the target of Dog-rose x Field-rose (Rosa arvensis) i.e. Rosa x irregularis. So I headed up the hill behind the village (part of VC63) where I knew I could expect both parents to see how I got on. Surprisingly well is the answer, and this does seem a good gateway hybrid to get you looking closer and appreciating the subtleties.

Graham and Primavesi in the BSBI Rose Handbook describe Dog-rose as very much the blank canvass species, against which you look for the differences that help to distinguish the other species and hybrids. That proved good advice for my current search as while the hybrid is reassuringly intermediate it might easily be overlooked if you don't know what individual characters preclude Dog-rose and which in combination suggest Field-rose.

The first thing I honed in with on my first likely candidate was the pedicels - were they glandular? (Note - this is not a character discrete to Field-rose). The answer was yes, and variably so but generally at a much lower level than would be the case for Field-rose. The next thing I noticed was the relatively length of the pedicels, very variable but with many much longer than would be expected in Dog-rose or indeed most other native rose species. The fruit, sepals, foliage and stems also looked intermediate with characters of Field-rose but beefed up by the Dog-rose genes. On some bushes there was variability of fruit set with a high proportion abortive. Similarly some bushes had biserrate leaves which again is a Dog-rose character. Another useful character is the intermediate prickles which are often aggregated. I hope the following photographs help illustrate some of these traits. My next challenge is to start to record it in VC64 and 31 as I'm sure it will be common wherever the two species meet.

Note the glandular pedicels

Note the variation in pedicel length with some to 3cm, while the outer fruit are proportioned more like Field-rose and the inner like Dog-rose

Intermediate stems and foliage, on a sprawling and suckering thicket

Towards the middle of the stem, 3 prickles can just be made out in close association (aggregated)

Ilkley Moor Baht 'at

I finally made it, after 7 years of not really trying, up Ilkley Moor this week in the heat of Tuesday and probably unwisely without 'at. This is of course a well botanised site so I was not expecting to add much new to the plant list, and in this light I did quite well.

The first good find was a new stand of the non-native Silver Lady's-mantle (Alchemilla conjuncta), extending its range into a new tetrad.

Not a new location, but of interest to me was the enigma that is Cut-leaved Bramble (Rubus laciniatus). No one really knows this species origins, or whether it is native or endemic to Britain. It is certainly not native in Yorkshire, but in comparison with the thug that is Himalayan Giant (Rubus armeniacus), I am more than happy to welcome it.

By far the best find of the day, apologies in advance for the over-exposed photo I blame the low late season sun!, was a colony of Knotted Pearlwort (Sagina nodosa) along the the historic alignment of Keighley Road. From the data available to me, it does not appear to have been reported from the Moor for decades, so I am pleased to have refound it. The associated Eyebright (Euphrasia) is giving me headaches and is one for the BSBI referee.

To end with, here is the view from Addingham High Moor where the carpets of Heather (Calluna vulgaris) were at peak bloom. Scenic as it is, it is important not to forget what an impoverished habitat this is for native flora. Over a century of over-management for grouse does not leave room for much else, and it is not a very satisfying habitat for a botanist. That said, Ilkley Moor seems to be suffering the opposite effect i.e. a legacy of under-management resulting in an ever increasing dominance of Bracken (Pteridium aquilinum). There must be a middle ground somewhere, but it is a challenge to find the most favourable balance in the modern world where traditional agriculture and land management is no longer economic.