Northern Marsh Orchid

Northern Marsh Orchid  Dactylorhiza purpurella


The orchid family (Orchidaceae) is a large family which contains over 25,000 species worldwide and a large number of those species face extinction. In part, this is because orchids have such precise requirements and as a result, habitat destruction can have a more marked effect than it does on less selective species. Also, many orchids have very precise pollination requirements.  All the pollen is bundled into paired pollinia (see below) that require a specialist courier or insect pollinator. For this reason, orchids may be more vulnerable to depletion of insect numbers compared to grasses for example. Grasses chuck huge amounts of pollen into the air and leave it to chance that some of it will end up in the right place.
No orchids are common in the UK and although Dactylorhiza species are among the more common it is still exciting to find them in a city-centre park and every year it comes as a relief to me when they reappear in their usual haunts.  Furthermore, most years there is a surprise or two when orchids appear where I don't expect to see them; growing between some paving stones or between the stone blocks at the edge of the lake for example.

Taxonomy

Orchids are monocotyledons and have leaves with parallel veins and flower parts (petals and sepals) in threes. The name orchid derives from the appearance of the bilobed tubers below the ground that were thought to resemble testicles.
Orchids are so much of a departure from generalised flower form that they even have their own terminology.
Labellum - the prominent lower lip of the flower (see below)
Pollinia- the pollen is packaged into paired sacs rather than being freely released by stamens.
Column- that bears the stigmas, stamens and the pollinia.
Viscidium - a sticky disc that glues the pollinium to the head of a visiting insect.
A detailed review of Orchid anatomy and pollination is outside the scope of this blog. For an easily readable account, I recommend chapter 7 of Darwin's Backyard by James T Costa.
1. Schematic of Orchid anatomy. Sepals (1,2 and 3) and petals (4,5 and 6) in threes.
Lower petal enlarged to form the labellum

Because of their rarity, it came as surprise to me to find what I think is Northern Marsh Orchid growing in Leazes Park. The first place I saw one was growing through the block paving at the margin of the Lake. Sadly this disappeared after a few days and I imagine that somebody picked it. However, there is another location but I am not telling you about that. Instead, here are some pictures.

2. Northern Marsh Orchid growing through the undergrowth.

3. Northern March Orchid showing flowers in a raceme (youngest flowers at the top).
Prominent leaf-like bracts also visible

4. Individual flower showing the viscidium and pollinia

Where to find orchids in leazes Park

I am not telling you, you will have to find them for yourself. Don't expect them to 'jump out at you' as the tropical orchids you find at the garden centre do. Our native orchids are often hidden in long grass and have a beautiful subtlety about them that rewards getting down on your hands and knees to study the patterns on the labellum and look into the flower to see the curious apparatus for pollination.

5. Two magenta marsh orchids hiding in the long grass 


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