Wednesday, 13 September 2017

Fruiting Orchids

A nearby meadow which the owner closed to the public earlier this year because dog-walkers were not respecting it, can now be visited again.  

Five orchid species grow in this meadow, though one, Greater Butterfly Orchid, (Platanthera chlorantha) I personally have not seen there.  Yesterday I did find fruits of three, Pyramidal (Anacamptis pyramidalis), Common Spotted (Dactylorhiza fuchsii) and Bee (Ophrys apifera).

Pyramidal seems to set seed then enter the senescence phase quickly.  The seeds had almost all gone.  Common spotted, which flowered at about the same time still had some seed pods, and indeed one plant was still a little green.   Most of the orchid leaves had withered.


                              Fruiting Common Spotted Orchids

I made some measurements of the seed pods, because in the senescent state they are difficult to tell apart.  Of course Common Spotted does still have remnants of  bracts amongst the seed pods, but it is a feature that is easily overlooked and can be mistaken for the remains of unpollinated flowers. The pods of Common Spotted got smaller moving up the inflorescence, but this was not true of Pyramidal spikes. It turned out that Pyramidal seed pods were a little longer, but a little thinner than those of Common Spotted. Indeed the pod length to width ratio for the two species was quite different:

Pyramidal                 Pod length to width   0.43±0.19  (n=10)
Common spotted      Pod length to width   0.56±0.12   (n=18)

The difference between the two proved to be statistically significant.   Is this a possible identifier?   I need to collect samples from elsewhere to see if it might be or whether this finding is site specific.

The third orchid typically found in this type of habitat, Chalk Fragrant Orchid, occurs in very small numbers and I could not find any in fruit for comparison, and again I need to look a a little further afield, if I have not left it it too late this year..

It is definitely autumnal now - Blackthorn and Black Bryony in fruit, Ivy in flower.



                                     Black Bryony

Black Bryony is toxic due to the presence of calcium oxalate, and seems to be avoided by animals. Estimates suggest that 30 - 40 berries can be fatal to humans; oddly I decided not to test this out.

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