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Small White Orchids
20th June 2012

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Introduction

Thanks to a good ‘botanical friend’ we have recently been introduced to another charming Orchid species. This one is not found on the shores of Lough Allen but we have always felt our brief was to include the catchment area, hills and vallies, surrounding Lough Allen. These Orchids occur in Cavan close to Dowra and the Shannon River. They are a very pretty Orchid, an elusive Orchid, and one which may be dying out. The North West is an important area for this species. It is flowering now... early June 2012.

Up in the hills near Dowra, looking north into Cavan, grows this charming little plant. Very small, very rare, but very attractive when viewed close up!

A tall (for Small White) very fresh and complete plant. It’s rare to come across a specimen like this — it was only 20cm tall — with leaves and flowers in perfect condition.

The Small White Orchid only flowers for about 3 weeks around the beginning of June. They can appear insignificant but when you get to notice them and understand the nature of their ways, they are utterly fascinating and beautiful.

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Close up of the flowering spike where some of the details of the flower can be seen. Each flower has a twisted stalk, a wide short and pointed bract, overlapping sepals and petals are similar colour, with the brown pollinia just about discernable in the bottom two flowers. The structure of the flowers are shown in greater detail below.

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We should emphasise that these plants are very small. It is just due to the marvels of modern cameras that we are able to reproduce them so large here. We have put up several photographs because this is an unusual and elusive plant and even people who live near it may never been able to appreciate it in such detail. This, of course, is a plant needing conservation and protected both sides of the border. (Photographs have been taken using a Lumix G3.)

A vast amount of interesting detail and up to date facts can be found in A. & D. Love’s article on this species in their Biological Flora of the British Isles.

Below is a short extract describing its distribution...

“
P. albida is a small, native orchid of mesotrophic to acidic grasslands, or heathlands. It is now largely confined to the northern and western parts of the British Isles; like other grassland orchids, it has declined drastically in the southern parts of its range, consequently being classified as vulnerable in Great Britain and endangered in Ireland.
”

Two more images showing the variety of habitats this plant may occupy. The one on the left growing tall in a species rich unimproved pasture.

The specimen on the right, on top of a very low grass covered wall, enabling us to pose the Orchid against a backdrop of the rolling hills of north west Cavan.

Habitat of the Small White.

Small White Orchids occur in clusters. They are hard to find, because of their size, but when you find the right place many may be found together. The two on the right formed a string of at least 10 specimens growing along a low grass covered stone wall. Typically these were just remnants of stone or clay walls. If they were more than 60 cms high, or overgrown, or tightly grazed by sheep, the Small White Orchid was not to be found.

The converse side of this fussiness is that it can become easier to identify suitable areas and to look for them in the most likely areas. For example, we have sought them on the east facing side of the Playbank and Sliabh an Iarainn overlooking Lough Allen — but they have not been found yet. These specimens were recorded in the foothills on the northside of The Playbank and in raised mounds (presumably Drumlins) in the valley below.

They are often found on these ditches but also occur in open fields. Perhaps the ones in ditches are easier to spot? Or alternatively the fields may be either too wet or too overgrown. Most of these Orchids we have seen have been on north west facing slopes and we are wondering are these drier and more sheltered from the driving rain of the south west facing slopes on the Lough Allen side of the mountain. Plus, they get the evening sun in the locations they choose to grow?

Anatomy of the Small White.

A fairly typical Orchid structure, these plants belong to a small Genus called Pseudorchis with only one species occurring in Ireland.

They are typically a circumpolar boreal species found on Arctic coastlines of Scandinavia, Iceland, Greenland and North America. Unlike Lough Allen’s other rare orchid, Spiranthes romanzoffiana, they do have a European presence outside of the British Isles occurring in Alpine regions of the south as well as northern Europe.

Associated Plant Species.

Plants are like Humans. They are choosy about where they live and who they live with. A clue to a suitable home for Small White orchids can often be got by recognising the common flowering plants that grow in the same environment.

The Small White Orchid is often found in association with:

Devil’s Bit Scabious

Tormentil

Heather

Cross-leaved Heather

Lousewort

Milkwort, Common and Heath

Holly and Bilberry

Marsh Violet

Heath Spotted Orchid

Butterfly Orchids

Landscape and Distribution of the Small White Orchid.

The photograph above shows the cliffs of The Playbank, one of the highest mountains in Co. Leitrim. The foothills,
in the foreground, lie in Co. Cavan and are productive areas for this Orchid.

The Small White thrives on gentle mountain slopes (Left) and rounded glacial hills alongside the Shannon River. (Right)

Traditional farming practices support the existence of this increasingly rare orchid. If these fields are heavily fertilised the orchids seem to suffer at the expense of the grass. Very often neighbouring fields can alternatively be rich, or very poor, in orchids — for no obvious natural reason.

The field on the left in front of the forest is very rich in these orchids, likewise fields beyond the forest. Further extension of conifer planting will further limit the range of this rare plant.

Very often these sites appear to face North West and this seems to meet the Orchids requirements better than other conditions and aspects.

Aspect and micro-climate seem to play a part in the distribution of the Small White Orchids. The picture on the left is of a small broken down stone ditch running through the small field in front of the forest. This ditch is covered with a wide variety of flora and was a very productive site for this orchid.

In the photograph on the left you can see some of the plants typically associated with the Orchid, Holly, Heath Spotted Orchids, Heather, Scabious, Bilberry and grasses. A ditch like this no more than 60cm high with the right altitude and aspect, is well worth searching in early June for the Small White Orchid

The ditch on the right, coming from one of the ‘drumlins’ running along the centre of the valley, is much more broken down with very stunted trees sheltering between the exposed stones. It appears that, though lower down, this site is less protected by the shelter provided by the Playbank for those fields directly below the summit of the mountain. i.e. the wind sweeps down into the valley and results in more eroded ditches and prostrate trees. Needless to say, we found no Pseudorchis albida here!

Whereas the Lesser Butterfly Orchid and the Small White can be seen together, the Butterfly Orchid is much more tolerant of rain soaked fields. The specimens shown on the right were taken from the drumlin shown above where the ground was much wetter underfoot than the well drained fields of the foothills. Whilst any orchids are an inviting sign, a field with very large numbers of Lesser Butterfly Orchids may not be happy hunting ground for the Small Whites. They are more likely to be associated with Greater Butterfly Orchids.

In such wet areas the Small White is much more likely to occur on slightly raised and well drained areas such as the grass covered wall or the edges of drains and ditches. Many fields will only have them occurring in this manner but in the field shown above right they were equally at home in the middle of the field with rich garss and scabious growth, along with this pretty Marsh Violet, shown left.

Here is a larger photograph of the ‘field habitat’ of the Small White Orchid in the Cavan/Leitrim borders... The Small White is on the left; you can see how hard to see it is! The orchid on the right is a Heath Spotted orchid. This field had been ‘fertilised’ using farmyard manure and dired mats of manure and straw were visible in places. However this technique seemed to be suiting both the grasses and the Small Whites.
This was the only site we came across this June where the numbers of Small White Orchids was comparable in the middle of the field as on the ditches — they were just much harder to find in the open field, often being shorter than surrounding grasses and other vegetation. They did seem to benefit from breaks in the grass cover often caused by mats of manure forming breaks in the grass cover. In previous years, we have been told, most of the plants were in the fields and not along the ditches.

It seems that both the distribution and recording of these Orchids may vary from year to year depending on weather conditions and timing of visits. If the grass is short and the ground dry, they may appear in open fields. If the grass is lush and the ground wet, the specimens occurring on the drier grass covered low walls and alongside drains may do better?

This is certainly a most attractive and interesting plant. We hope that some of the photos at the top of this report may stimulate your interest, and that the curious distribution and the very localised occurrence of this plants may intrigue you — as it has done us. Whereas this plant does occur in Leitrim these occurrences are a considerable distance away from Lough Allen. We have made several diligent searches on similar slopes at similar altitudes along the foothills of the mountains on the east shore of Lough Allen.

But, to no avail! And, as we get to know this species, we are not surprised. The eastern slopes of The Playbank (which are in Co. Leitrim) as well as the foothills of Bencroy and Sliabh an Iarainn all seem much wetter and predominated by damp loving plants such as Sphagnum and Rushes. No suitable habitat such as occurs round the corner in Co. Cavan was identified. It seems that the aspect and the prevailing direction of rainfall works against this lovely little plant occurring above the shores of Lough Allen.

However, it is very much part of the larger area and we are very pleased to include it as a significant orchid for the broader Lough Allen area — along with the beautiful Irish Lady’s Tresses — to come later in the Summer!

Last thoughts on P. alba for 2012.

This plant has just about finished its flowering season now. It is a valuable and declining species. The area in which it grows is traditional undeveloped mountain grazing. It occurs at a very defined altitude, 100m - 200m, and under very defined conditions that we have described above.

While observing this species we were struck by particular facies in which this plant occurs on the Leitrim/Cavan border. In other areas it has different factors defining its distribution. But in this population, is it just altitude and aspect that regulate its distirbution? The Map on the left places the two significant groups of orchids we observed, one kindly introduced to us, the other found through careful study of their habitat. (Many thanks to all those who shared their time with us.) The geological data on the map is courtesy of the Geological Survey of Irelands GSI Datasets Public Viewer. A brilliant and fascinitating service — Thank You! The Orchid data is our own research. The intersect between the orchid data and the bedrock data can only be approximate at this resolution.

Many Orchids love a calcareous or limey soil. Just think of the well know orchids of the Burren in Clare — a Karst landscape. But the mountains of north Lough Allen are not limestone; they are Upper Carboniferous shales and sandstones. Are these plants getting their calcium fix through particular drainage patterns or are they, like the local very rare orchid, Spiranthes romanzoffiana, an unusually acid tolerant species of orchid?

The grey coloured area represents the Bellavally Shale Formation which is wet and calcareous. Is this possibly a source of calcium rich water which may encourage the Orchids to grow here, or is it purely the altitude. (In other countries and latitudes they grow at much different altitudes?) The yellow rocks are very thick banded formations of the coarse sandstone also found (in thinner strands) around the shores of Lough Allen. It is dense rock resistant to water and (presumably) rather acidic.

Maybe the boundaries of these different strata in some way explain the occurrence of this very rare plant — at least in this particular location. It’s just a theory... but curious though?