Species of the Month - June 2012

Greater Butterfly Orchid  &  Lesser Butterfly Orchid

Platanthera chlorantha                 Plananthera bifolia


These orchids flower in June and July.  They are easily told apart from all other orchids, but are often confused with each other.

Platanthera chlorantha
Greater Butterfly Orchid
  Platanthera bifolia
Lesser Butterfly Orchid

The flower has 3 sepals and 3 petals.  The lower petal hangs down like a strap and the lower 2 sepals form the wings at the sides.  The upper sepal and the upper 2 petals are folded together to form a hood at the top.  Underneath this hood are the 2 pollinia.  In the GBO, as the picture above shows, these pollinia are far apart at their lower ends, though they converge upwards.  In the LBO the pollinia are parallel and close together all the way down.  Once you know this difference, the species are easy to tell apart, provided they have fresh flowers.  Plants that have not yet flowered or that have finished flowering cannot be reliably identified, but it's worth noting where they are and going back when they are in flower.

The two species are genetically almost identical and have only diverged in recent times to accommodate the behaviour of different  moths.  The GBO is pollinated by Noctuid moths which stick their whole heads in between the pollinia to get at the nectar.  The pollinia then stick to the moths' eyes and are transferred to the next flower they visit.  The LBO is pollinated by hawk moths who simply poke their long proboscis between the pollinia, which are close together to ensure that they stick to the proboscis when the moth leaves.

Platanthera chlorantha
Greater Butterfly Orchid
  Platanthera bifolia
Lesser Butterfly Orchid

The two species have different habitat requirements.  Both grow in open ground, but GBO prefers a richer, drier, more alkaline soil, such as roadside verges or hay meadows, while LBO will grow on poorer, wetter, acid soils, including heather moorland.  Despite this, there is a remarkable tendency for the two species to be found close together.  When you find one, look for the other in ground nearby that's a bit drier/wetter as appropriate.  When counting a population, don't assume they're all the same kind!

LBO is classified as "Vulnerable" and is one of the most rapidly declining wild flowers in the British Isles (Harrap & Harrap 2009).  Its stronghold is in N & W Scotland where there is still plenty of unimproved grassland and heath, but even here it is under threat due to changes in land use, including grazing levels.

GBO is classified as "Near Threatened" but is more widespread across Britain than LBO.  Where it occurs on road verges they should be managed sympathetically for it.  In some places it may be threatened by the spread of bracken.


Please send in your sightings using the form below.  Send a photo of an open flower to sightings@lnhg.org.uk if not sure which species you have found.

Date of sighting 
Species 
Location 
Grid reference 
Number seen 
Name of finder 
Your name (if different) 
Email (not needed if I already know it!) 
Habitat and any other details 


 

By filling in this form you agree that the information contained in this form may be collated and disseminated manually or electronically for environmental decision-making, education, research and other public benefit uses in accordance with the LNHG data access policy.  Your email address will not form part of the record and will not be passed on to anyone.

Carl Farmer
SNH
G Biological Records Manager


Sightings so far

4 Jun: Jan Hamilton found a patch of a dozen LBO's at North Cuil.

9 Jun: Sallie and I saw LBO in Glengour on the Lochaber Biodiversity Day outing.

17 Jun: Jan found another patch of LBO's in a different place at North Cuil

19 Jun: Bob Groves found one LBO at Little Ganavan.

21 Jun: Jan found 7 GBO's at Duror

25 Jun: Bob found some GBO's at North Connel.

7 Jul: Gela found 2 GBO's at Kilchrenan



Note you can still send in records for past species of the month.  Here is the list of species we've had so far:

May 2012 - Small Copper
Apr 2012 - Green Tiger Beetle
Mar 2012 - March Moth
Feb 2012 - Barren Strawberry
Jan 2012 - Brambling
Dec 2011 - Red Squirrel
Nov 2011 - Hazel Gloves
Oct 2011 - Small Tortoiseshell
Sep 2011 - Fly Agaric
Aug 2011 - Grass of Parnassus
Jul 2011 - Golden-ringed Dragonfly
Jun 2011 - 7-spot Ladybird
May 2011 - Green Hairstreak
Apr 2011 - Townhall Clock

Mar 2011 - Frogspawn

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All photos and other content copyright Carl Farmer except where stated