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Dr Andy Scobie,
Project Officer

Cairngorms Rare Plants Project
Scottish Natural Heritage,
Achantoul, Aviemore,
Inverness-shire,
PH22 1QD

Tel: +44 (0) 1479 810477
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The species
Lesser Butterfly-orchid

Lesser Butterfly-orchid image panel

Description and ecology:

This attractive perennial orchid produces a tall, loose flowering spike of striking white flowers during the all too brief flowering period which commences in late June and is over by mid-July. The flowers have a distinctive long, straight, undivided lower lip and lateral wings projecting from either side. The large, shiny and oval leaves occur in pairs at the base of the flowering stem and have parallel veins along their lengths. Lesser Butterfly-orchid plants can only be reliably identified when in flower, as floral characters are the key to distinguishing this species from the closely related Greater Butterfly-orchid (Platanthera chlorantha). Download the Identification Guide for notes on how to identify them.

The flowers of Lesser Butterfly-orchid become more strongly scented around dusk and produce large quantities of nectar in their spurs which can only be reached by an insect with a sufficiently long proboscis. Night-flying moths are the likely pollinators of these flowers but the particular moth species that pollinate the orchid in Scotland have yet to be identified.

Following pollination, the ovary of each flower swells then ripens to produce a capsule that splits down the sides. Each capsule contains several thousand dust-like seeds which are dispersed by wind. Capsule development and maturation appears to take a long time in Lesser Butterfly-orchid with green un-dehisced capsules sometimes remaining on the fruiting spikes until the end of September/early October.

Like many other orchids, the roots of Lesser Butterfly-orchid form a symbiotic relationship with mycorrhizal fungi. Due to their extensive network of mycelia, the fungi have a high capacity for absorption and assist with the uptake of water and mineral nutrients from the soil in return for a supply of carbohydrates from the orchid.

Mycorrhizal fungi are also likely to be critical during the stages of seed germination and protocorm development when the developing orchid may be entirely dependent upon the fungus for nutrition until the first leaf is produced. The time from seed germination to flowering takes three or four years in cultivation, and this may take even longer in the wild.

Habitat:

Lesser Butterfly-orchid occurs in unimproved grassland, heathland, woodland edges, road verges and rough on golf courses, on acidic to slightly basic soils. This species frequently grows in association with other orchids, Heath Spotted-orchid (Dactylorhiza maculata), Heath Fragrant Orchid (Gymnadenia borealis) and Small-white Orchid (Pseudorchis albida) being the most typical companions. The presence of these three orchid species at a site is likely to be a good indication of potential Lesser Butterfly-orchid habitat.

The maintenance of a short, open sward appears essential for the persistence and spread of Lesser Butterfly-orchid, and the majority of good sites for the species are usually either seasonally grazed or cut. However, the intensity and timing of grazing or cutting is critical. Heavy grazing or cutting during the flowering period can prevent the orchid from flowering and setting seed and, over time, this may ultimately lead to the disappearance of the species from a site. Equally, under-grazing can be a problem leading to the development of a tall and dense sward which may shade out the orchid.

Occasionally Lesser Butterfly-orchid occurs in mixed populations with Greater Butterfly Orchid, highlighting an overlap in habitat and management requirements for these two closely related species. However, Greater Butterfly-orchid appears more tolerant of taller, denser swards than Lesser Butterfly-orchid.

Distribution and status:

Lesser Butterfly-orchid has undergone a 33% decline in the UK since the 1970’s. The species is widespread in the UK but Scotland is the stronghold, and in particular the west and north of the country.

Follow the links below to view a UK distribution map:
BSBI UK Distribution Map
NBN UK Distribution Map

In the Cairngorms National Park Lesser Butterfly-orchid is rare and very localised, restricted to just a handful of sites in the Aviemore – Boat of Garten – Nethy Bridge area with a few older records from the Glen Tilt and Glen Fender area and an outlier near Tomintoul. However, one of these sites is among the largest in Scotland with several thousand plants.

View the CNP distribution map here:
CNP Distribution Map ( PDF File )

Populations of greater than 100 flowering individuals are not common. Small populations of 1 or 2 flowering individuals are more typical.

Lesser Butterfly-orchid has been identified as a conservation priority in the UK Biodiversity Action Plan and the Species Action Framework for Scotland and is included on the Scottish Biodiversity List.

Reason for decline and current threats:

1) Loss of habitat through agricultural improvement.

The drainage, application of fertilizer and herbicide, and ploughing and re-seeding of rough grasslands and lowland heaths to improve their productivity is a major cause of decline for Lesser Butterfly-orchid along with many other associated grassland species.

2) Unsuitable grazing management.

Heavy grazing during the flowering period of the Lesser Butterfly-orchid, preventing flowering and seed production, and limiting recruitment and spread over time, may ultimately lead to the disappearance of the species from a site. Too little grazing, or no grazing at all, especially during early spring and autumn/early winter, can lead to the dominance of tall and dense grasses and sub-shrubs creating a sward that is unsuitable for Lesser Butterfly-orchid.

3) Cutting during the flowering period.

The cutting of grasslands, road verges, and the rough on golf courses during the flowering period of Lesser Butterfly-orchid, preventing flowering and seed production, may ultimately lead to the disappearance of the species from a site.

4) Encroachment of scrub/ woodland regeneration.

Abandonment of regular grazing at some sites leading to the encroachment of scrub and regeneration of dense woodland causing the loss of grassland species, dependent upon a degree of grazing and disturbance, such as Lesser Butterfly-orchid.

Action for Lesser Butterfly-orchid in the Cairngorms National Park:

1) Increased recording and monitoring of Lesser Butterfly-orchid in the Park.

The location of all known populations of Lesser Butterfly-orchid in the Cairngorms National Park will be established, increased recording of the species will be encouraged, and searches will be conducted at historical sites and in areas of suitable habitat. Accurate GPS location data and basic monitoring data will be collected at all sites. This data will be used to provide a baseline against which to measure future change.

2) Implementation of conservation action.

Considerable research has already been undertaken on this species as part of SNH’s Species Action Framework, providing vital information on the habitat and management requirements of the species. Utilising this information, land managers will be advised on management actions to promote the establishment, persistence and spread of Lesser Butterfly-orchid at sites in the Park and this will include:

Large scale habitat management

  • Implementation/maintenance of favourable grazing or cutting management at existing sites, historical sites and in areas of potentially suitable habitat, ensuring the provision of a sufficient summer grazing break to permit flowering and seed production.
  • Restoration of rough grassland which has reverted to birch scrub.

 
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