More on fragrant orchids and their identification

Back in July I put down some thoughts on identifying the three fragrant orchids following a visit to Waitby Greenriggs in Cumbria; distinguishing between them is not easy. 

I have now done some further analysis because  over the summer I gathered data from another 7 locations where fragrant orchids occur, although not sadly from Clay Lane Meadow which is only 2 km away.  Frustratingly it  was closed off because of damage cause by irresponsible dog walkers. 

Marsh fragrant (Gymnadenia densiflora)

Chalk fragrant (Gymnadenia conopsea s.s.)

 

Heath fragrant (Gymnadenia borealis)

                                                                   The locations were:

• Helsington, Cumbria - Heath fragrant
• Rampsons Farm, South Stainmore - Heath and Marsh fragrant
• Garrow, Perthshire - Heath fragrant
• Keltneyburn, Perthshire - Heath fragrant
• Wye Down, Kent - Chalk fragrant
• Eades Meadow, Worcestershire - Chalk fragrant
• Sheepscombe, Gloucestershire - Chalk fragrant
• Waitby Greenriggs, Cumbria - Chalk, Marsh and Heath fragrant.

In all I made measurements on 40 plants: 

• Spur length (in most cases)
• Sepal length and width
• Angle of the sepal above or below the horizontal (+ or -)
• Number of flowers (in most cases)
• Leaf width (in most cases)
• Width and length of the labellum
• Width and length of the central lobe (except in most of the Heath fragrants where it is not readily distinguishable).

I then looked for measures that can be used for differentiation.  The first step was to decide what a particular plant was which immediately introduces bias because I relied mainly on the floral parts, such as the size of the labellum lobes.  The gold standard, DNA analysis, was not a possibility.  The keys in Stace 3rd edition were not wholly reliable, and with a revised edition of that reference on the way, hopefully there will  be more insights. The results in summary were as follows.

There was significant variation and the boundaries between species on a particular characteristic overlapped.   Nevertheless it does seem possible to separate out the three species.  Easiest is to pick out Heath fragrant.  I found statistically significant differences (using a T-test) between it and the others on labellum width and length, spur length, and the two ratios which I think are the most useful because they avoid absolutes which might be affected by environment and latitude, viz. labellum width to length and sepal length to width.   The former is not a surprising result because my initial allocation was probably weighted  towards this characteristic.

The other two were harder to separate, but on three parameters there was a statistically significant difference (using a T-test):  angle of sepals to the horizontal, labellum width to length and sepal length to width.  Given the variability and species overlap, I would look for best fit against each of them.

I did not measure the height of each plant nor the height of just the inflorescence.  A pity because it is probably worth looking at further, though I suspect there will be latitudinal effects, with northern plants on average shorter than those further south.   It was also noticeable that the inflorescence of Chalk fragrant plants had a mor lax appearance, and what might be very useful is the ratio of the number of flowers to the length of the inflorescence.  

I should also mention habitat and the common names define what is likely in marshes, downland and essentially north and west Scotland, but it is not 100% predictive.  The Helsington plants of heath fragrant for instance are overlying a base of limestone, so there is probably a cap of more peaty soil over it.

Looking forward there could be some significant  advances in fragrant orchid disaggregation.  I have mentioned the new edition of Stace which comes out in late January,  but Richard Bateman and Ian Denholm, BSBI's joint orchid referees, will publish a  note on identification in the January edition of BSBI News, to be followed later in the year by an academic paper on the subject.   So next summer fragrant orchids will become easy peasy, at last!

The Commonest Orchid in Britain and Ireland

It's November, miserable and grey.  We have sleet this morning.   Earlier this week I had just two moths in the light trap, and that is probably it for this year.  No other insects around.   Nada.

It's time for indoor botany.   I am preparing a little presentation for my village garden society on Britain's wild orchids and in doing so natural questions pop up such as  'how common / rare are they' and 'where do you find them'.   Reading newspaper headlines it the phrase is always 'rare orchid'.

I have been a member of BSBI for at least 25 years.  I have been on a few field trips, which are mainly plant recording events, but because my identification skills for anything other than orchids, gentians and saxifrages, are very limited my contributions are little better than nothing.   So why remain a member?   Well there are benefits and a significant one is access to the database derived in part ironically from those recording trips.   It is terrific, and it was to this database I turned  so that I could work out how common or otherwise orchids actually are.   I analysed records for this century for all the orchid species by vice county.   These vice counties have I think been unchanged since 1852 in Britain when they were introduced by Watson, (Praeger introduced the same concept for Ireland in 1901) unlike the administrative county boundaries, which change with every passing whim of politicians. 

There have been taxonomic changes this century.   I eliminated records for Dactylorhiza majalis, which is now mostly reclassified in the most part to D. kerryensis, an Irish species, and the fragrant orchid aggregate, Gymnadenia conopsea s.l (sensu lato = in the broadest sense) was split in the early 2000's  into 3 species, formerly recognised as sub-species, (Heath fragrant, G. borealis; Marsh fragrant, G. densiflora; Chalk fragrant, G. conopsea s.s (sensu stricto = in the narrowest sense)) 

Heath Fragrant Orchid

The results were surprising.   The database gives no hint as to plant abundance, and therefore one record on one day in one place is equivalent to 1000's in lots of places every year, so there are limitations.  Nevertheless it is the best we have, and the results were surprising.   The commonest orchid (i.e. the most widespread) was Common spotted orchid (Dactylorhiza fuchsii) which occurred in 152 of the 153 vice counties in Britain and Ireland.   Three other orchids, Common twayblade (Neottia ovata), Early purple (Orchis mascula) and Heath spotted (Dactylorhiza maculata) were not far behind and occurred in 150, 149 and 148 vice counties respectively.   By contrast 4 orchids were only found in one vice county; Ghost orchid (epipogium aphyllum) made its only appearance this century in 2009, and the Hebridean marsh orchid (Dactylorhiza evudensis) is not now recognized as a separate species and should not really be included.  (I saw it this year on North Uist in the sand dunes there.)

Common Spotted Orchid, Eades Meadow, Worcs

Common Twayblade, Cornbury, Oxfordshire

                                               

Early Purple Orchid, The Burren, Ireland

Increasing the granularity of the analysis by looking at the data by hectad (10km x 10km squares), in Britain only (excluding Ireland), there are around 3500 hectads.  Common spotted orchid is still the commonest, appearing in 2121 hectads (61%), but the top order ranking changes a little with the next three reshuffled.  Heath spotted orchid is in 1744 hectads (50%), Early purple is in 1308 (37%),  and Common twayblade in 1205 (34%).

The most orchid-rich vice county was Westmorland, where I was born and raised.   The administrative county disappeared years ago and is now remembered only as a service station on the M6, and this vice county name.  It has 31 species, and seems to be a cross over point between northern and southern species, amplified by the upland there.   My present home, the Oxfordshire vice county, comes third with 29 species.   Two small Scottish vice counties have only 6 species.  The 3 pictures below were of plants at Helsington near Kendal.

Dark-red Helleborine, Helsington 

Fly Orchid, Helsington

Fly Orchid, Helsington

But wherever you live in Britain and Ireland you are never far from an orchid of one sort or another

Leaf Miners

Things quieten down in autumn, and its a chance to look at wildlife that is easily overlooked.  Fitting into that category are leaf miners, flies and moths which at the caterpillar stage feed and grow in the leaves of trees and other plants.  I have seen a number of postings in blogs and on Facebook (eg Plants of Skye, Raasay & the Small Isles) describing leaf miners that have retarded leaf senescence leaving green islands in an otherwise brown leaf, so I started looking in the hedge in front of my house for similar examples and this widened out into a more general search for leaf miners.  To identify them I relied on British Leaf Miners - with a heavy dependence on miners being specific to host plants - and the captions on a few examples that follow may be entirely wrong, if that dependence is misplaced.  But it's a start, and the best thing is that they are easy to find in quiet moments.

 Phyllonorcyter cerasicollela, Wild Cherry

 

Phyllonorcyter cerasicollela, Wild Cherry

Phyllonocyter hostis on Crab Apple

Phyllonocyter hostis on Crab Apple

Stigmella tityrella on Beech

Stigmella microtheriella on Hazel

Butterfly Orchids in Oxfordshire; Bats Nearer Home

An eclectic combination.   

Over the last few days I compiled the results of surveys I did of the two butterfly orchid species in Oxfordshire for a status update for the Flora Guardians programme.

I had some site references from the Flora Guardians programme itself and then added in records (primarily from the year 2000 onwards) from the BSBI Distribution database, access to which and the analysis it allows is well worth the BSBI subscription alone.  Unfortunately there is a misalignment of boundaries because the administrative county contains all of BSBI's vice county 23 (which I used) but also bits of vice county 22.   No matter, I ended up with 26 localities where Greater butterfly orchid has been seen this century, and 5 where Lesser Butterfly orchid has been seen.  I also added a site which I have been studying over the last 2 summers, and probably holds the largest number of plants in the county but was on neither database.

I surveyed only 6 of the Greater butterfly orchid localities, though almost certainly these contain the bulk of the plants.  I also surveyed 2 of the 5 Lesser butterfly orchids locations.   Greenfield Farm (to which there is no public access) had over 500 plants of which 196 produced flowering spikes, an increase of on 2017.  The plants are in beech / ash woodland, and thus quite heavily shaded; there is no real herb layer, but there is regrowth of ash and beech and a tangle of brambles.  Habitat maintenance is selective; in the 2017/18 winter the bramble was cut back in three quarters of the site but left in the other quarter.  Dog's mercury is becoming a problem in one corner, developing a heavy smothering sward, perhaps encouraged by increasing light levels (which we are trying to monitor) because the ash is suffering from die back. 

BBOWT's  Warburg reserve has both species. An underestimate for certain,  I counted around 40 flowering plants of Greater butterfly orchid,  scattered quite thinly through the reserve apart from one hotspot.  Generally they were in scrub regrowth in areas cleared some years back.  Numbers have been stable since 2015, when comparable annual counts started.   Lesser butterfly orchid is rare and at Warburg there were only 4 flowering plants growing amongst scrub on the edge of rides.   There was also one flowering plant of the hybrid P. x hybrida, last seen (recognised?) in 2003.    Some modest scrub clearance around the existing plants might help.

Elsewhere I counted 28 scattered flowering Greater butterfly orchids at Bald Hill, English Nature's Aston Rowant reserve on top of the hill amongst low scrub, and a few plants on the Cornbury estate adjacent to a footpath.

So, a few sizeable colonies of Greater butterfly orchids, a species which is probably under-recorded because there may be more in some of the Chiltern woodlands.   By contrast, lesser butterfly orchid is just abut hanging on at Warburg, though there has only ever been a few plants there.  Unless the 3 locations that I have yet to look at have plants, it might be that those few remaining at Warburg are the only examples in Oxfordshire.

Leaves count! Cornbury

Greater butterfly orchid, Bald Hill

Lesser butterfly orchid with scale, Warburg

Closer to home I have been out bat detecting  having bought a new toy a  bat detector which works on my phone, an Echometer touch.  It constitutes a microphone which plugs into a smart phone and links to an app. Its clever, providing a chart of a bat echolation sound in what it calls real time expansion or as a heterodyne signal.   For lazy people like me who just want to know what bats are out there, it also gives an identification which is correct most of the time, and it gives a gps location.    We are in to November, yet even so, possibly because it was a mild evening  I picked a noctule and a common pipistrelle near home.  

Common pipistrelle sound wave