Greater Butterfly Orchid (
This is the plant that I have studied and photographed most, from a 7-year study on Skye (described in three papers) and a continuing study of an Oxfordshire population now in its 5th season.
Etymology
Platys = broad, anthera = flowery
chlorantha = greenish
1597 Gerard. 'Orchis ornithophora candida...which resembleth the White Butter-flie... Hampstead heath...High-gate in the wood belonging to a worshipfull gentleman of Kent named Master Sedley of Southfleete' VC16,21 (Pearman)
The Plant Year
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First leaves to fruiting. Ard Dorch, Skye |
The Plant
Habitat
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| Bald Hill, Oxfordshire 8.6.18 (IMG 7972) |
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Keltneyburn, Perthshire 2.7.17 (IMG 5759) |
Whole Plant
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Greenfield, Oxfordshire 26.5.20 (IMG 6699) |
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Warburg, Oxfordshire 24.5.20 (IMG 6486) |
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Greenfield, Oxfordshire 31.5.20 (IMG 6931) |
Height of plant (average):
Greenfield, Oxfordshire 36.6cm (n=150)
Ard Dorch, Skye 25.9cm (n=433)
Inflorescence
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Ard Dorch, Skye 3.7.15 (IMG 4317) |
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Greenfield, Oxfordshire 31.5.20 (IMG 6941) |
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Greenfield, Oxfordshire 2.6.20 (IMG 6994) |
Average inflorescence:
Greenfield, Oxfordshire 8.8cm (n=50)
Number of flowers on a spike:
Greenfield, Oxfordshire 12.7 (n=150) Flower density 1.4 flowers / cm
Ard Dorch, Skye 10.8 (n=439)
Flower
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Greenfield, Oxfordshire 26.5.20 (IMG 6704) |
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Greenfield, Oxfordshire 20.5.20 (IMG 6316) |
Greenfield, Oxfordshire (n=67) Flower width, tip of one sepal to the other: 22.2mm
Labellum width: 3.5mm
Labellum length: 14.9mm
Angle between pollinia: 36.9° (cf Platanthera bifolia)
Angle of lateral sepal below horizontal: 13.5°
Lateral sepal width: 4.2mm
Lateral sepal length: 11.8mm
Spur
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Greenfield, Oxfordshire 4.6.19 (IMG 4597) |
Greenfield, Oxfordshire 32.9mm (n=109)
Ard Dorch, Skye 24.7mm (n=22)
Spur length decreases moving northwards
Pollinia
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Greenfield, Oxfordshire 9.6.19 (IMG 4395) |
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Greenfield, Oxfordshire 9.6.18 (IMG 3086) |
Measurements:
Greenfield, Oxfordshire (n-67) Distance between viscidia 4.4mm
Distance between bases of pollinia 2.1mm
Caudicle length 3.7mm
Description
Stems to 60 cm, leaves 5 - 15cm (Stace). The leaves are often chewed, such that length is not very helpful. By contrast, leaf width of a mature plant is, and provides a useful discriminator against Platanthera bifolia.
Leaves
2 paired, blunt, broad basal leaves, occasionally 3 if the previous year's tuber has not fully died away. A few small bract like leaves on the stem.
Average width of bottom leaf of flowering plants:
Greenfield, Oxfordshire: 47.3mm (n=150)
Ard Dorch, Skye: 33.6mm (n=453)
First leaves on emergence:
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Greenfield, Oxfordshire 8.4.19 (IMG 9971) |
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Greenfield, Oxfordshire 10.4.18 (IMG 3929) |
Leaf Edge
Leaf Edge, Upper Side x100 (IMG 4775-81S) Field of View 1 mm
Roots
Two tubers depending on the time of year; the aerial stem develops from food stored in the tuber formed in the previous year, while a new tuber with its associated bud for next year, forms in late summer. (Summerhayes). Roots are short and thick.
Seeds
Average dimensions (n=143): Length 0.752mm
Seed Pods
Habitat
Wide tolerance, and in the south is equally at home in open fields, grassy slopes and in comparatively dense woodland. Further north it is found in open grassy banks or slopes, in heathy fields, hill pastures and meadows. (Summerhayes). Whilst in the south it seems to prefer neutral to alkaline soils, it is not a strict calcicole, and the association with calcareous soil is often exaggerated. The pH of the soil at Ard Dorch, Skye, was around 6.5 for example.
Mychorrhiza
No data.
Pollination and Fruit Set
Quite a variety of night-flying moths, attracted by scent and reward of nectar in the spur. The pollinating moth therefore has to have a sufficiently long proboscis. Commonly quoted as pollinators are hawkmoths, but the plant is not pollinator specific and in the UK at least 12 species have been identified - trapped with pollinia attached to head parts (cf, Platanthera bifolia has similar pollinators but pollinia attach to the mouth parts because of the narrower spur entrance
Flowering time
Analysing the BSBI records post 2000, but excluding the Channel Isles, and any records where the date is not given in full gives 12156 records for Britain and Ireland. I further reduced this number by excluding any dates other than May through July. I also separated out the very large number of records for Pembrokeshire and treated this vice county separately. This left 4908 records and I think it can be assumed that the vast majority of records are made when plants are in flower. Looking at the median date for these records split into latitudinal zones, and separately Pembrokeshire and Ireland gives the following flowering dates across the country:
Britain, south of a line through Bristol, 1692 records, median date June 5
Distribution in Britain and Ireland
Distribution Worldwide
It belongs to the Eurasian element of British orchids, found in most of Europe extending eastwards to Korea and western China, and down to Asia Minor and Persia. The distribution of its relative Platanthera bifolia is similar but P. chlorantha is rather more southerly and more of a lowland species. (Summerhayes).
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| Leaf Edge, Lower Side x100 (IMG 2938) Field of View 1 mm |
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Leaf Edge, Lower Side x100 (IMG 8680) Field of View 1 mm |
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Leaf Edge, Upper Side x100 (IMG 2924-8S) Field of View 1 mm |
Very variable from entire to shallowly toothed. Between 10 and 16 shallow teeth per mm.
Leaf Tip
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Leaf Tip, Upper Side x 40 (IMG 2933) Field of View 2.5 mm |
Average angle of the leaf tip 94.5° (n=6).
Roots
Two tubers depending on the time of year; the aerial stem develops from food stored in the tuber formed in the previous year, while a new tuber with its associated bud for next year, forms in late summer. (Summerhayes). Roots are short and thick.
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Tuber with scale 28.7.14 (IMG 4373) |
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Tuber with scale 9.1.19 (IMG 8559) |
Seeds
Average dimensions (n=143): Length 0.752mm
Width 0.136mm
Length to width ratio 5.55
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Typical seed (IMG 3835) |
Seed Pods
Average dimensions (n=59): Length 16.98mm
Width 4.07mm
Length to width ratio 4.34
Angle of attachment to stem (n=33): 12.2° to upright
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Seed pod examples (IMG 1227) |
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Fruit spike (IMG 6944) |
Wide tolerance, and in the south is equally at home in open fields, grassy slopes and in comparatively dense woodland. Further north it is found in open grassy banks or slopes, in heathy fields, hill pastures and meadows. (Summerhayes). Whilst in the south it seems to prefer neutral to alkaline soils, it is not a strict calcicole, and the association with calcareous soil is often exaggerated. The pH of the soil at Ard Dorch, Skye, was around 6.5 for example.
Mychorrhiza
No data.
Pollination and Fruit Set
Quite a variety of night-flying moths, attracted by scent and reward of nectar in the spur. The pollinating moth therefore has to have a sufficiently long proboscis. Commonly quoted as pollinators are hawkmoths, but the plant is not pollinator specific and in the UK at least 12 species have been identified - trapped with pollinia attached to head parts (cf, Platanthera bifolia has similar pollinators but pollinia attach to the mouth parts because of the narrower spur entrance
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Elephant Hawkmoth hovering over orchid, Greenfield 8.6.17 (IMG 4275)  Marbled Coronet with pollinia attached, Skye.© Keith Sadler |
Averages of my measurements of fruit set (number of fruits compared to number of flowers) are summarised as:
Greenfield, Oxfordshire: 34.3% (n=150)
Ard Dorch, Skye: 28.6% (n=309)
There is considerable variation; regularly a whole spike will have no seed pods, but very occasionally all the flowers on a spike develop into fruits. There is also significant annual variation due to climate conditions in June and July. The middle quartiles of a spike have higher fruit set than the top or bottom quartiles.
Fruit set seems to be much higher in mainland Europe. In 26 European studies fruit set ranged from 53 to 91% with an average of 78%. (Claessens and Kleynen)
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In fruit, almost ready to release seed. Ard Dorch, Skye 23.9.14 (IMG 5920) |
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In fruit, the green phase before turning brown. Greenfield, Oxfordshire 3.8.20 (IMG 0717) |
Flowering time
Analysing the BSBI records post 2000, but excluding the Channel Isles, and any records where the date is not given in full gives 12156 records for Britain and Ireland. I further reduced this number by excluding any dates other than May through July. I also separated out the very large number of records for Pembrokeshire and treated this vice county separately. This left 4908 records and I think it can be assumed that the vast majority of records are made when plants are in flower. Looking at the median date for these records split into latitudinal zones, and separately Pembrokeshire and Ireland gives the following flowering dates across the country:
Britain, south of a line through Bristol, 1692 records, median date June 5
Britain, north of Bristol, south of Birmingham excluding Pembrokeshire, 782 records, median date June 11
Pembrokeshire, 6813 records, median date June 28
Britain, north of Birmingham, south of Manchester, 536 records, median date June 24
Britain, north of Manchester, south of Carlisle, 304 records, median date June24
Britain, north of Carlise, south of Glasgow, 255 records, median date July 3
Britain, north of Glasgow, south of Inverness, 824 records, median date June 30
Britain, north of Inverness, 125 records, median date July 2
Ireland, 390 records, median date June 27
There is a clear link between flowering date and latitude.
My counts at Greenfield, Oxfordshire (north of Bristol, south of Birmingham) are typically around June 5, whilst the date for the first flower to appear on a spike, averaged across all the plants in the population for Ard Dorch, Skye (slightly south of Inverness) ranged from 19 June to 7 July depending on temperatures in the weeks before. Whether early or late, this flowering date was consistently 7 to 9 days later than the equivalent for a sympatric population of Platanthera bifolia. First leaves appeared around 40 days before flowering.
Distribution in Britain and Ireland
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BSBI Records 2000 - 2020 |
Found in 129 vice counties with most records from Pembrokeshire VC45 (6830) and South Wiltshire VC8 (399) though the former's total is significantly inflated by exact data for individual plants in a single locality in repeat annual surveys. In 2000-20 it was found in 2098 monads, and surprisingly it appears to be spreading (monads in 1960-79: 581, and in 1980-99: 1371), though there may of course have been far more recording activity in the more recent decades.
Distribution Worldwide
It belongs to the Eurasian element of British orchids, found in most of Europe extending eastwards to Korea and western China, and down to Asia Minor and Persia. The distribution of its relative Platanthera bifolia is similar but P. chlorantha is rather more southerly and more of a lowland species. (Summerhayes).
None
Hybrids
Platanthera chlorantha hybridises sparingly with its relative P. bifolia = Platanthera x hybrida, where populations are sympatric. See under P. bifolia.
Platanthera chlorantha hybridises sparingly with its relative P. bifolia = Platanthera x hybrida, where populations are sympatric. See under P. bifolia.
No other hybrids are recognised in Britain and Ireland.
References
Kühn et al: Orchids of Europe and the Mediterranean - Kühn, R., Pedersen, H. and Cribb, P. 2019
Claessens and Kleynen: Flower of the European Orchid - Claessens J and Kleynen J 2011
Summerhayes: Wild Orchids of Britain - Summerhayes VS 1951
Stace: New Flora off the British Isles - Stace C 4th Edn, 2019
Summerhayes: Wild Orchids of Britain - Summerhayes VS 1951
Stace: New Flora off the British Isles - Stace C 4th Edn, 2019
