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Lesser Butterfly-orchid

(Platanthera bifolia)

Lesser butterfly-orchid © Trevor Dines

Lesser butterfly-orchid © Trevor Dines


Beautiful and delicate, this orchid is one of the rarer gems to be found on our rapidly diminishing grasslands.

Lesser butterfly-orchid has a single flowering spike that can reach up to 30 cm in height. The flowers themselves are white with a slight greenish tinge. Two 5-8cm blue-green elliptical-oblong blunt leaves that arise at an angle from the base of the plant.

It is similar to the greater butterfly-orchid but differs slightly in appearance (see 'Did you know?' at the bottom of the page) and scent.

Distribution

Formerly widespread across much of England, a major decline was already evident by 1930. Overall lesser butterfly-orchid has been lost from 75% of its recorded range in England. Losses have occurred throughout the range, but especially in the east; east Midlands, Yorkshire and Humber. Lesser butterfly-orchid is much reduced even in it’s strongholds of Cumbria, Dartmoor & Exmoor and Wessex. Across Wales, lesser butterfly-orchid is widely scattered but the majority of sites are in Cardiganshire. Cae Blaen Dyffryn Nature Reserve in Carmarthenshire hosts a population that can exceed 3000 individuals in good years in a single 9 acre (3.7 ha) field. It is also present across Scotland, Northern Ireland and Ireland.

Habitat

This species tolerates a remarkable range of conditions. In most remaining sites in the north, the west and the New Forest it tends to occur in wet acidic bogs, mires and flushes, on damp heathland and in acidic damp grassland such as culm and rhos grassland. Elsewhere, it also occurs in dry neutral to calcareous grassland and in semi- to deep-shade in scrub and woodland.

Status

Classified as ‘Vulnerable’ and is included as a species “of principal importance for the purpose of conserving biodiversity” under Sections 41 (England) and 42 (Wales) of the Natural Environment and Rural Communities Act 2006. Lesser butterfly-orchid is also noted on the Scottish biodiversity list of species of principal importance for biodiversity conservation in The Nature Conservation (Scotland) Act 2004 and is noted on the Northern Ireland priority list of threatened species compiled in 2010.

Key threats

A long-lived tuberous perennial, this species can tolerate heavy grazing for a short time but requires stable management and seed production over many years for populations to increase. Many populations have declined slowly over decades with drainage, eutrophication and light grazing leading to scrub encroachment and over-shading all playing their part. Agricultural improvement of grasslands including re-seeding and over-seeding of pasture, use of fertilisers and conversion of grassland to arable land use has also affected this species. Lesser butterfly-orchid seedlings rely on a symbiotic fungus for their early development which is very sensitive to fertilisers and fungicides.

Best time to see

June and July whilst flowering.

Did you know?

The best way to distinguish the lesser butterfly orchid from the similar greater butterfly orchid is by the two pollen sacs, which are a couple of millimetres long, vertical, parallel and close together forming an ‘II’ shape. Greater butterfly-orchid pollen sacs are 3-4 mm long and converge above while being widely spaced at the base in an inverted ‘V’ shape.