Species Action Framework: Management Guide - Lesser butterfly-orchid (Platanthera bifolia)
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Scottish Natural Heritage Species Action Framework: Management Guide Lesser butterfly-orchid (Platanthera bifolia)
The Species Action Framework (SAF)
programme ran between 2007 and 2012 to
deliver targeted management action for 32
priority species in Scotland. Lesser butterfly-
orchid was one of the species selected
for conservation action having suffered a
dramatic decline across Britain over the
past five decades, leaving Scotland as its
remaining stronghold.
This guide aims to summarise the knowledge
gained on lesser butterfly-orchid over the 5
year SAF programme and provide guidelines
for the successful future conservation
management of this species and its habitats
in Scotland.
Written by Liz Lavery and Andy Scobie, September 2013.
All images © Andy Scobie unless otherwise stated.
ISBN: 978-1-78391-479-1
FRAMEWORK
Contents What is lesser butterfly-orchid? 2 How do you identify it? 3 Where does it occur in Scotland? 4 Why is it important? 6 What are the key threats to lesser butterfly-orchid? 8 Managing for lesser butterfly-orchid 10 What does it need? 10 Site specific management 12 Key steps to successful management for lesser butterfly-orchid 12 Unimproved lowland pasture and old hay meadows 13 Heathland and open hill ground 17 Road verges, golf courses and lawns 18 Restoration of neglected sites 19 How do you monitor it? 20 What to record 21 Survey and monitoring approaches 22 Further information 23 Acknowledgements 24
What is lesser butterfly-orchid?
Lesser butterfly-orchid (Platanthera bifolia) is a long-lived perennial herb of
grassland and heathland habitats. It flowers during June and early July when
a loose spike of 5 to 30 striking-white flowers are produced at the top of the
flowering stem 15 to 30 cm tall. The oval leaves occur in pairs at the base of
the flowering stem, hence ‘bifolia’ which means ‘two leaves’.
Around dusk the flowers emit a strong, sweet scent attracting night-flying
moths which pollinate them. The nectar is held at the end of a long, tube-like
spur and can only be reached by certain species of moth. When a flower
is successfully pollinated, a capsule is produced which slowly swells, then
ripens, splitting down the sides to release several thousand dust-like seeds in
August and September. The tiny seeds are dispersed by wind.
Each year, the orchid re-grows from a tuber below ground containing stored
nutrients from the previous summer season. A second, new tuber forms beside
it, equipped with a bud on the top, from which new growth will arise during
the next season. The roots form a symbiotic relationship with mycorrhizal fungi
which assist the orchid with uptake of water and nutrients from the soil.
Specific fungi are also required for seed germination and development, when
the orchid may be entirely dependent upon the fungus for nutrition until the
first leaf is produced. Initial growth and development takes place below
ground, and can last for several years. It may take 3 or 4 years before the first
flowering spike is produced.
2
How do you identify it? Lesser butterfly-orchid
Lesser butterfly-orchid can only be reliably identified when in flower. Flowering
lasts for a short period, only 3 to 4 weeks during June and early July, presenting
a narrow window of opportunity to look for and monitor this species. The green
developing seed capsules, which remain after the flowers have gone, are
inconspicuous and difficult to distinguish from those of other orchids.
Two species of butterfly-orchid occur in the UK: lesser butterfly-orchid
(Platanthera bifolia) and greater butterfly-orchid (P. chlorantha). Butterfly-
orchids can be distinguished from other orchid species by their loose spike of
white flowers tinged with green which have a distinctive long, strap-shaped,
undivided lower ‘lip’ and lateral ‘wings’ projecting from either side plus a
long, narrow spur to the rear. The shiny, oval and unspotted leaves occur
in pairs at the base of the flowering stem, with one to five small, narrow upper- Greater butterfly-orchid
leaves on the flowering stem.
Lesser butterfly-orchid looks very similar to greater butterfly-orchid, except that
it is smaller in all of its parts. It is not uncommon for both species to occur at
the same site. By far the most reliable way to tell them apart is to examine the
angle and distance between the two club-shaped pollinia (pollen sacs) in the
mouth of the flower. In lesser butterfly-orchid the pollinia lie close together
(c. 1 mm apart) and parallel forming a ‘II’ shape. In greater butterfly-orchid
they are widely-spaced at the base (c. 3-4 mm apart) forming an inverted ‘V’
shape (Fig. 1).
Figure 1. Position of pollinia (arrowed) in flowers of
lesser butterfly-orchid and greater butterfly-orchid –
the key character for telling them apart.
3
Where does it
occur in Scotland?
Lesser butterfly-orchid has a
widespread distribution in Scotland
but is most common in the
northwest mainland and Hebrides
(Fig. 2). It is a scarce plant in much
of central, eastern and southern
Scotland. It is found mostly in small
numbers, often in widely scattered
groups of a few flowering spikes.
At the majority of Scottish sites less
than 10 flowering spikes appear
each year. Populations of more than
100 are unusual, and only a very
few exceptional sites support 500
or more.
Figure 2. Distribution of lesser
butterfly-orchid in Scotland showing
hectad (10 km square) records made
between 2000 and 2012. Data from
national Species Action Framework
survey, and the Botanical Society of
Britain and Ireland.
4
Lesser butterfly-orchid occurs in
a broad range of heathland and
grassland habitats in Scotland.
Many sites can be described as
‘wet’ or ‘damp’. It is regularly found
in wet heath, along the margins
of boggy ground, on tussocks in
marshy grassland, and at the edges
of wet flushes in moorland. It also
occurs on drier sites including dry
grassy heathland and herb-rich
grassland in unimproved pastures,
old hay meadows, roadside verges
and rough on golf courses.
It grows on mildly acidic through
neutral to slightly calcareous soils
overlying sands, gravels and clays.
Lesser butterfly-orchid appears
more tolerant of acid soils than
greater butterfly-orchid, but its
occurrence is often localised to
areas where slight flushing reduces
soil acidity.
Damp grassland habitat of lesser
butterfly-orchid on South Uist, Outer
Hebrides. © Stewart Taylor.
5
Why is it
important?
Lesser butterfly-orchid is a
widespread species which has
undergone a dramatic decline in
the UK. It is classified as ‘vulnerable
to extinction’ on the Vascular Plant
Red Data List for Great Britain
(2005) and is a UK Biodiversity
Action Plan priority species. It
has no statutory conservation
protection, except where its habitat
is a notified feature within a Site
of Special Scientific Interest
(SSSI). The UK stronghold for
lesser butterfly-orchid occurs
within Scotland making this a
highly important area for its future
conservation.
Flower-rich grassland supporting
lesser butterfly-orchid near Brora,
Sutherland. © Robin Ward.
6 8
Lesser butterfly-orchid is an indicator of ecologically
important sites, many of which are unimproved pastures
and old meadows shaped by a long history of low-input
grazing and/or cropping for hay. Here, lesser butterfly-
orchid regularly occurs in the company of a rich diversity
of wild flowers, often with several other orchid species,
along with a wide range of associated biodiversity,
including many insects and birds, both common and rare.
Once more commonplace across Britain and Ireland,
these sites have suffered widespread losses since
the mid-1900s mainly as a result of agricultural
intensification. As a consequence, many species
associated with these habitats have undergone dramatic
declines as they have become increasingly confined
to occasional corners of fields and road verges, which
have escaped cultivation, and to areas of marginal land
unsuitable for improvement.
It is vital, therefore, that remaining examples of these
habitats are maintained and restored, not only to
conserve lesser butterfly-orchid, but for the range of
biodiversity they support.
Other orchid species, such as heath
fragrant-orchid, often grow together
with lesser butterfly-orchid.
7
What are the key threats to
lesser butterfly-orchid?
• Agricultural improvement of rough
grassland and lowland heath
The draining, ploughing and re-seeding of rough
pasture and old meadows, along with applications of
fertiliser and herbicide, to improve their productivity
is a major cause of habitat loss. Lesser butterfly-
orchid and many associated wild flowers are unable
to persist amongst the dense, fast-growing swards
resulting from these changes in management.
• Heavy grazing or cutting during late spring
and early summer
Orchid leaves and flowering spikes are susceptible
to damage from heavy grazing or cutting too early
in the season. When flowering spikes are lost, this
limits seed production and potential for seedling
recruitment and spread. Where heavy summer
grazing is sustained year on year, orchids and other
associated wild flowers can be completely ‘grazed-
out’ over time.
Orchid leaves and flowering spikes
are vulnerable to grazing, trampling
and cutting from when they first
appear in May through to seed set in
August. 8 10• Too little grazing or cutting
Where there is too little grazing or cutting, or none at all, the development
of dense tussocky vegetation and encroachment of scrub can lead to the
gradual exclusion of lesser butterfly-orchid over time. Under-grazing of
‘species-rich’ grasslands is an increasingly common problem where sites
are often stocked at insufficient levels, or not grazed for long enough, to
eat down the sward in late summer/autumn.
• Woodland establishment
Woodland regeneration or planting schemes can result in the loss of
suitable grassland and heathland habitat for lesser butterfly-orchid which
is excluded following the cessation of grazing and development of a
woodland canopy.
• Damage from heavy poaching and nutrient enrichment
Some light poaching can be beneficial, creating open sites for seedling
recruitment amongst dense swards. However, the structure and
composition of grasslands can be altered, and orchid tubers damaged,
following heavy poaching and localised nutrient enrichment associated
with overwintering and supplementary feeding of large numbers of
livestock on small or wet sites.
Insufficient grazing can result in
development of dense ground
vegetation, scrub and woodland
leading to the exclusion of lesser
butterfly-orchid over time.
9Managing for lesser butterfly-orchid
What does it need?
1. The opportunity to grow, flower and set seed – promoting persistence
and spread to new areas. Orchid leaves and flowering spikes are most
susceptible to damage from grazing and cutting during mid-May to mid-
July, but seed capsules can take a further six to eight weeks beyond this to
mature and shed their seed.
2. Short and open vegetation – seedlings and adult plants are susceptible
to shading from dense vegetation or scrub and can be suppressed by a
build-up of dead plant litter or ‘thatch’ if excess growth is not removed
each year by grazing or cutting at appropriate times.
3. Bare or disturbed ground – seeds need to come into contact with
the soil to germinate. Light poaching from animal hooves and recently
disturbed ground, such as spoil from ditch-clearing, can help to provide
suitable open ‘micro-sites’ for seedling establishment.
4. Maintenance of existing drainage patterns and flushing – where
orchids grow in damp or wet areas it is important not to alter the water
table as this can cause changes to soil and surrounding vegetation
creating conditions less favourable for the orchid.
10Lesser butterfly-orchid thrives at sites
where a well-timed grazing regime
maintains a short and open sward,
with a sufficient summer grazing
break to permit growth, flowering and
seed production.
11
12Site specific Key steps to successful management for lesser
management butterfly-orchid
Lesser butterfly-orchid occurs in 1. Identify the location and full extent of the orchid population and the
a variety of habitats in Scotland vegetation in which it occurs. This will help to target effective management
under a diverse range of to the right areas or fields.
management regimes. Some sites
receive very little management 2. Protect sites from agricultural improvement (including drainage of wet
whilst others are regularly grazed areas and applications of fertiliser, herbicide, lime, slurry and farmyard
or cut. As a consequence, a single manure) and woodland regeneration schemes which cause unfavourable
approach to managing for lesser changes to the habitat of the orchid.
butterfly-orchid is both difficult
to describe and unlikely to be 3. Establish and maintain a well-timed grazing and/or cutting regime
successful. Instead, some key permitting orchids to grow, flower and set seed whilst removing the growth
principles can be applied to help of vegetation each year to maintain a favourable open sward and prevent
tailor appropriate management litter build-up (see detailed guidance below).
regimes to individual sites.
If the orchid is already present at 4. Monitor the site and orchid population, adapt the grazing or cutting
a site in high numbers then it is regime where fine-tuning of sward conditions is required and manage
likely that the existing management orchid areas to keep them free of bracken and scrub.
regime is already favourable. In
these situations, the best possible 5. Avoid overwintering large numbers of livestock on small or wet sites
course of action is to ensure that where this may lead to excessive poaching. Where supplementary feeding
a similar pattern of management is is required to extend periods of grazing through autumn and winter, site
continued in the long term. feeding stations well away from orchid areas.
12Unimproved lowland pasture and • On larger sites, moderate stocking from mid to late
July onwards, especially with cattle, can be effective
old hay meadows at controlling the sward whilst still permitting a
proportion of orchid fruiting spikes to survive and
Many lesser butterfly-orchid sites fall within this category shed their seed.
which includes damp acid grassland, dry herb-rich • On smaller sites, where there is a greater risk that
grassland, and rush pasture, where regular grazing and, all fruiting spikes will be grazed-off, limit grazing
occasionally, hay cropping are the key management until late August then stock to graze down summer
tools. The timing and intensity of the grazing or cutting growth.
regime is important to the survival of lesser butterfly-
orchid at these sites. • As a general rule, all sites should receive a significant
period of grazing between the end of August and
Grazing management: November taking the sward down to a max height of
5-10 cm over much of the site. This can be achieved
• Release sites from heavy grazing pressure between by stocking heavily for 3-4 weeks or with lower
mid-May and mid-July allowing orchids to grow stocking for a longer period.
and flower. A ‘shut-up’ or exclusion period may be
required on smaller sites, whilst reducing stocking • Spring grazing can be beneficial to control fresh
to low levels is sufficient on extensive sites where growth, especially on more productive sites. Remove
animals are free to roam in and out of areas with or reduce stocking by mid-May at the very latest.
orchids. • Where desirable to stock sites heavily throughout
• There is a delicate balance to be struck between summer, electric fencing can be used to protect
allowing enough time for the orchid to set seed, orchid areas. Remove to permit grazing from late
which can take until late August, and reinstating August.
sufficient grazing to control the sward before • Cattle are especially good for removing large
vegetation starts to die-back and become less quantities of grass in late summer. Periodic light
palatable to livestock in late summer. poaching by cattle can also open up seedling
recruitment sites amongst dense swards.
13• Sheep tend to target flowering
spikes in summer but are good
for close-cropping a sward
over autumn/winter and can
be effective at controlling
regenerating scrub and tree
seedlings.
• Orchid populations on sites
managed as part of extensive,
low-input grazing systems are
by far the most successful.
• Supplementary feeding to
support grazing through
autumn/winter should not be
ruled out where this could
help to achieve favourable
sward conditions. Stocking at
appropriate levels for the site
and locating feeding stations
well away from orchid areas can
reduce undesirable impacts of
heavy poaching and nutrient
enrichment.
Take care to site feeding stations well
away from areas with orchids. © Glyn
Satterley/SNH.
14One of the largest populations of lesser butterfly-orchid in
Scotland occurs in short-cropped (5-10 cm) dry heathland
and species-rich grassland at a 5 ha site in Stathspey in the
Cairngorms National Park.
The site is managed as part of a single larger 16 ha grazing
unit stocked with around 40 cows and followers in periods
from early summer through to winter. Cattle are free to roam
between the unimproved orchid meadow and improved
pasture within the wider grazing unit. They typically don’t visit
and graze the orchid meadow until mid-August, providing the
orchids with an opportunity to flower and set seed.
15Cutting management:
• Lesser butterfly-orchid also persists on a few croft
sites in the north of Scotland managed for a late hay
crop cut in late July/August. The process of turning
and drying the hay over several days allows seed
capsules to ripen and seeds to be shaken out before
bailing. Cutting earlier risks removing fruiting spikes
before the seeds have matured.
• This management is most successful where hay
cropping is followed by a period of ‘aftermath
grazing’ in late summer/ autumn and preceded by
light grazing in spring.
• Early cutting for silage production and associated
sward improvements is detrimental to orchids
and other wild flowers and are therefore not
recommended.
• At sites where it is proving problematic to graze at
sufficient levels to remove the build-up of vegetation
each year, cutting can provide an alternative. It is
essential that cuttings are collected and removed.
Cut as late as possible, preferably before late
September, to allow orchid seed capsules to mature.
Cutting sites too early in the summer
can remove orchid seed capsules
before they are ripe.
16Heathland and open hill ground
At these sites lesser butterfly-orchid usually occurs
in naturally open areas of vegetation in wet heath and
mire, on the edges of wet flushes, or on slopes over thin
gravelly soils. Management input is typically very limited,
or none at all. However, extensive grazing by livestock
or red deer can be important for keeping sites open and
preventing scrub from invading.
Here, it is important to:
• Graze orchid sites to maintain a diverse mosaic of
short, open grassy areas and taller areas of heather,
and keep flushes open, whilst preventing scrub and
bracken from invading.
• Protect sites from heavy grazing between mid-
May and mid-July, especially by sheep, to permit
flowering.
• The importance of red deer as winter grazers should
not be overlooked.
• Take care if burning heather. Evidence suggests that
lesser butterfly-orchid can withstand light burning,
but high intensity fires are likely to be damaging.
© Ian Strachan.
17Road verges, golf courses and
lawns
Small strips of grassland and heathland on road verges
and golf courses, and occasionally in lawns, can provide
an important refuge for lesser butterfly-orchid and a
range of associated wild flowers. Cutting is the key
management tool though some unfenced verges are
grazed by livestock and deer.
Here, it is important to:
• Cut the site each year to remove the build-up of
vegetation after the growing season.
• Collect and remove cuttings, if left they can enrich
the soil and create a build-up of thatch unsuitable for
the orchid.
• Delay cutting until autumn, preferably not before late
September, to allow plants to flower, set and shed
their seeds.
• Inform local authorities of sections of road verge with
orchids and request that cutting is postponed until
late September and cuttings raked and removed
(where possible). Specialist tractor-mounted flail
collector mowers can be useful for
• Permit grazing by livestock or deer where this is managing small sites such as rough
likely to be a key factor in maintaining suitable open on golf courses where grazing is
vegetation. impractical.
18Restoration of neglected sites
At sites which haven’t received sufficient management
for a long period, actions to restore favourable conditions
for the orchid include:
• Clearing and removal of scrub to create open areas
for grazing or cutting.
• Cutting the site each year in autumn (late September
onwards) and removing cuttings. Additional raking
can also help to remove thatch and open up the
sward.
• A combination of late cutting followed by a period of
grazing over autumn and winter can be effective for
restoring a favourable open sward.
• Where appropriate, cutting can be substituted by
a suitable grazing regime in the long-term once
favourable sward conditions have been restored.
Heath fragrant-orchid with six-spot
burnet moth. Restoring sites for
lesser butterfly-orchid can help a
large number of other species.
19How do you
monitor it?
150 Wester Balgair
Monitoring is an important means
Glen Luss
of tracking long-term changes in
orchid populations in response Flanders Moss
to management. This can be 120
done very simply by counting the
Number of flowering spikes
number of flowering spikes each
year. It is typical for the number of 90
orchid flowering spikes at a site to
fluctuate naturally from year to year,
sometimes quite dramatically (Fig.
3), so it is important to make counts 60
over several successive years in
order to detect a general upward or
downward trend. 30
0
2006 2007 2008 2009 2010 2011 2012
Year
Figure. 3. Annual variation in flowering
population size at three Scottish lesser
butterfly-orchid sites. Data from Plantlife
Flora Guardian volunteers.
20What to record
1. Recorder – the name of the person who did the
survey;
2. Date – when the survey was done;
3. Location – note the grid reference of the site (from
GPS unit or 6-figure from map) and/or make a
sketch map showing the position of groups of plants
at the site;
4. Count – the total number of flowering spikes in the
population;
5. Extent – approximate area (length x breadth)
covered by the population.
Monitoring of lesser butterfly-orchid by
a team of volunteers at Loch Leven.
© Ian Borland.
21Survey and monitoring A B C
approaches
1. Small and discrete populations – re-visit the same
area each year to make a count of flowering spikes
then search out from this point in concentric circles
across the site (Fig. 4A) to detect new groups or
outlying plants.
2. Large and extensive populations – these can be
very difficult to count all at once. Walking transect Figure 4. Survey and monitoring approaches for lesser
butterfly-orchid:
lines spaced at intervals across the site is an
effective way of managing the task (Fig. 4B). Space A. small and discrete populations – concentric circles;
transects closer together (e.g. 2 m apart) where B. large and extensive populations – parallel transects;
orchids occur at high density, and further apart (e.g.
C. searching for new populations – zigzag across the site.
5 m apart) where they are at lower density. Bamboo
canes are useful for marking the ends of transects.
3. Searching for new populations – new discoveries
await those willing to search through suitable looking
areas, especially those near to existing sites. Walking
across the site in a zigzag pattern (Fig. 4C) is the
most efficient way of covering the ground, searching
more intensively in areas where you encounter
orchids. Please submit your monitoring data to: Plantife Flora
Guardians, Plantlife Scotland, Balallan House, Allan Park,
Stirling, FK8 2QG. scotland@plantlife.org.uk or to the
Botanical Society of Britain and Ireland.
22Further information
Recommended stocking levels for grassland and heathland habitats:
Chapman, P. 2003. Conservation grazing of semi-natural habitats. SAC Technical Note:
TN586. www.sruc.ac.uk/downloads/file/1128/tn586_conservation_grazing_of_semi-
natural_habitats
Grasslands and their management:
Hall, C. 2010. Management of species rich grasslands. SAC Technical Note: TN629. www.
sruc.ac.uk/downloads/file/749/tn629_management_of_species_rich_grasslands
Scottish Natural Heritage. 2010. Guide to types of species-rich grassland. SNH
Publications, Battleby, Perth. www.snh.gov.uk/publications-data-and-research/
publications/search-the-catalogue/publication-detail/?id=1734
Ward, S. & MacKintosh, J. 2001. Grasslands: Scotland’s living landscapes. SNH
Publications Battleby, Perth. www.snh.gov.uk/publications-data-and-research/
publications/search-the-catalogue/publication-detail/?id=39
Additional information on managing grassland sites for lesser butterfly-orchid and other
plant species can be found on the Plantlife Magnificent Meadows web pages.
For further information please contact:
Plantlife Scotland, Ballallan House, Allan Park, Stirling, FK8 2QG
scotland@plantlife.org.uk, www.plantlife.org.uk
Further information on the lesser butterfly-orchid carried out during the Species Action
Framework can be found at Lavery, E.L.D. 2016. Lesser butterfly-orchid. Version 1.0.
In The Species Action Framework Handbook, Gaywood M.J., Boon P.J., Thompson
D.B.A., Strachan I.M. (eds). Scottish Natural Heritage, Battleby, Perth. www.snh.gov.uk/
speciesactionframework
23Acknowledgements
This guidance was based on a wealth of information contributed
to the Species Action Framework national lesser butterfly-orchid
survey by volunteers, botanists, land managers and conservation
partners from across Scotland, without whom the production of
this document would not have been possible.
This document was produced as an output of the Cairngorms Rare
Plants Project with funding and support from the Esmée Fairbairn
Foundation, the Cairngorms National Park Authority, the University
of Aberdeen, and Scottish Natural Heritage.
About the authors
Liz Lavery is a freelance ecological consultant who worked on
the SAF lesser butterfly-orchid project between 2007 and 2012,
and is an expert on the orchid and its habitats in Scotland. Liz
continues to manage annual surveys of lesser butterfly-orchid by
the Plantlife Flora Guardian volunteers.
Andy Scobie is a conservation ecologist and botanist. As Project
Officer for the Cairngorms Rare Plants Project, which ran between
2010 and 2013, Andy worked on the conservation management of
lesser butterfly-orchid and a selection of other rare Scottish plants
in the Cairngorms National Park.
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