Hybrid Orchids
What are they?
As if some of our orchids were not difficult enough to tell apart, some species have a nasty habit of cross-pollinating with each other to produce hybrids. These hybrids are often fertile and can thus continue to cross not only with each other, but also to back cross with either of the parents. The result of this is what is known as a 'hybrid swarm', where a population of orchids at a single site can show more or less a full spectrum of intermediates from one original parent to the other. In extreme cases, one or both parents can eventually disappear through these hybridisation events, leaving a range of plants, none of which happily match any one species description.
Marsh and Spotted orchids in the genus Dactylorhiza seem most prone to this behaviour, perhaps suggesting that they are still rather close to each other genetically and progressive habitat and climate change since the past ice age may be driving this by bringing species that were once geographically separated into close contact with each other.
Where are they found?
Hybrids may occur anywhere that habitat diversity brings different species into close contact with each other.
Identification
The identification of hybrids is often somewhat presumptive, beginning with plants that do not appear to neatly match any of the good species. Careful checking of as many plants as possible in a population, together with the habitat type, may help in indicating which species are involved, while typical hybrids (at least first generation crosses) do tend to show a mix of features from the two parents. The species of marsh and spotted orchids can all be seen by (clicking here). Some hybrids are largely sterile and thus occur as isolated individuals with one or both of the parents; these plants can be easier to tackle than hybrid swarms as they stand out as clearly different from other plants around them.
Common Spotted x Southern Marsh Orchid Dactylorhiza x grandis
The most frequent hybrid, but largely sterile so usually occurs as isolated individuals with obvious examples of one or both parents. Usually a tall and stately plant with a large number of flowers in the spike. Flowers show the broad labellum of Southern Marsh Orchid with the more obvious central lobe of Common Spotted. Leaves lightly spotted with transverse blotches. Some plants rather resemble well-marked Heath Spotted Orchids but are usually much larger and growing in different habitat.
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Common Spotted x Early Marsh Orchid Dactylorhiza x kernerorum
A rather rare hybrid, but largely sterile so usually occurs as isolated individuals with obvious examples of one or both parents. Flowers show a rather narrow labellum from the Early Marsh Orchid parent with the more obvious central lobe of Common Spotted. Leaves unspotted or lightly spotted.
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Common Spotted x Heath Spotted Orchid Dactylorhiza x transiens
A rather rare hybrid, but largely sterile so usually occurs as isolated individuals with obvious examples of one or both parents where acidic and chalky habitats come close together. Flowers show the rather broad labellum of Heath Spotted Orchid with the more obvious central lobe of Common Spotted. Typically more robust than Heath Spotted Orchid and more like Common Spotted in overall spike structure, but with somewhat narrower leaves.
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