Hybrid Orchid – an analysis

During our recent trip to Scotland, Mike Waller and I visited a site for Pugsley’s Marsh Orchid – Dactylorhiza traunsteinerioides. We were particularly keen to see the “lapponica” form of this species, as we had never had the pleasure previously. I believe this is more recently renamed ssp “francis-drucei”

Such a mouthful. From now I will refer to them as “PMO” for ease.

The colony we visited was on a hillside alkaline flush with surrounding acid heath. This is supposedly a typical habitat. the lapponica at this colony were approximately 60-70 strong, and confined to a relatively small area.

They were quite consistent in appearance florally, with a lip that is longer than wide with three clear lobes, the side ones usually shorter than the central one. Whilst flowers were typically deep maroon and purple in colour, some had a paler background. Consistently, however, they were strongly marked with thick dark purple loops, with in particular a thick one curving round the side lobes, parallel to the edge.

The leaves weren’t particularly narrow (this species is also known as “Narrow-leaved Marsh Orchid”), but all were spotted. However, the spotting, whilst sometimes very heavy, did vary down to light markings. The amount of spotting on the leaves did not correlate with the amount of pigment in the flowers.

A couple of examples which were fairly typical of the population are shown below.

Other species close to the PMO were: Heath Fragrant Orchid – good numbers, in fine flower; Heath Spotted Orchid – smaller numbers, mostly in bud with the odd flower out; Early Marsh Orchid – two or three, pretty much over (form incarnata); Northern Marsh Orchid – a single plant, going over.

Close to the centre of the colony was a stand-out single plant which looked ostensibly like a Heath Spotted Orchid – certainly in terms of flower shape at least. However, it had the base colour and stronger patterning of Pugsley’s Marsh. Add to that it was in full flower, and was the second tallest plant on the hillside, and we considered that it must be a hybrid between PMO and Heath Spotted.

We took photographs, and both Mike and I pointed out that if we had seen photos on the internet in isolation, we would have doubted it was anything other than just a richly-coloured Heath Spotted (HSO). However, in the field, its colour tone (almost impossible to get a real impression of from photos alone) was distinctly PMO. The height of the plant indicated hybrid vigour. Compared to all the Heath Spotted we had seen over the last four days – and especially the ones nearby in this colony – it was twice as tall. As I said earlier, all the HSO here were in quite tight bud, yet this one was a week to ten days more advanced. HSO can have quite heavily spotted leaves (as we had discovered the previous day when we visited a supposed PMO site to discover HSO’s with heavily spotted leaves), therefore the leaf pattern is probably of no value in identifying this plant.

Note finally the heavy inside border loops of dark purple on the hybrid, and the shape of the inflorescence. HSO has a generally crowded and untidy inflorescence, with a round, flat top. The flowers start at the bottom singly often, and then overlap each other as they open. Whilst they can often have quite heavy loops, I am unable to find one where they are as thick and solid as on the hybrid. From the perspective of flower colour, HSO can also be quite a deep pink, but never with the PMO tone. And whilst a small sample, at the two colonies we saw HMO in Scotland (this one and the one at Corrimony the day before), when they are in damp flushes they seemed to be smaller than average, not twice the size.

In terms of parentage, with the two predominant species being HSO and PMO, with only a single example of Northern MO and two Early MO (no Common Spotted), added to the features described above, we conclude that this is indeed Pugsley’s Marsh X Heath Spotted. This hybrid has been recorded from Skye too. Of course, Pugsley’s is uncommon so the hybrid will be too. As more populations get checked, maybe more of these will be discovered and features can then be described.

Here are a couple of pictures of the hybrid, then some of both Heath Spotted and Pugsley’s Marsh.

Heath Spotteds from another colony earlier in the week and much further south – and also on a drier heath

The ones below were taken the day before, in a similar habitat at another site not far away. Note the leaves and the puny plants.

And some Pugsley’s for comparison:

There was another rather unusual plant in the colony, which unfortunately was still in tight bud.

It looked again like a Heath Spotted Orchid, and in fact was in bud, and apparently of a standard flower colour for that species.

However, it was over 30cm tall with very long, intensely spotted narrow leaves. Few-flowered and heavily bracted, there was little else to identify it. But if hybrid vigour is classed as an identification feature, then this plant had it and was one. Beyond this we cannot say, but of course would welcome comment from anyone better qualified than us.

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