Annual greater butterfly orchid counts in the Chilterns

A busy week.   I made a counts of greater butterfly orchids in 3 Chilterns locations.   At Greenfield farm there are around 500 plants, with 196 flowering spikes last year.  The plants are in two enclosures, fenced to keep out deer.   Plants are spreading outwards beyond the fences.   This year, the third, I counted all the plants, flowering and non-flowering, in the South enclosure but because the sward - dog's mercury, cleavers and nettles - was so dense in one area, I only counted flowering spikes in the other, North, enclosure.   And it rained. 

Both enclosures are shaded by young beech and ash, but because the ash has succumbed to die-back, light levels are increasing.   During the winter bramble was cut back and then in March I used a brush cutter to limit the dog's mercury in the North enclosure, though I don't seem to have made much impression on it. The heavy sward is choking out the orchids there.  

Sub-section with all plants marked

Almost ghostly in the early evening

  

A statuesque  greater butterfly orchid

The number of flowering spikes was dramatically less than last year; there were only 65 compared to 196 last year.

Snails were a significant problem in early April, so that this week plants that had been damaged then looked very unhappy, and the effect will probably be seen next year also because tuber growth will be impaired because of the leaf damage.  In one sub-section where I made detailed measurements of all the plants over a third of the plants had serious leaf damage, and the number of plants 'lost' i.e. nothing showing, was roughly a third of the total plants there last year, a rate of attrition far higher than we have seen in the last 2 years.

Leaf damage by snails

The enemy.

Winter was mild; and I wonder if this has led to a big increase in the number of snails.

Another possible cause of the fall in numbers might be climate.   The early autumn last year was very dry.   Could this have constrained tuber development and the ability of plants to flower?   Lots
of analysis to do in dark winter nights!

I made a count of the flowering spikes at Bald Hill, part of the Aston Rowant NNR.   A simple traverse but the same as last year, gave me a total of 18 flowering spikes, compared to 26 last year.  Unlike Greenfield these are plants out in the open, and although the reduction in numbers in percentage terms was not as great, it was noticeable that the plants were small.  One blessing was that it did not rain.

The third count of the week was of the butterfly orchids at Warburg NNR, the BBOWT reserve.   There it really did rain, so much so that my pocket voice recorder got damp and gave up on me and my waterproof clothing proved to be anything but.   I have yet to complete the analysis of the count but numbers there were also down on last year.   For instance I could find only 1 flowering lesser butterfly orchid (4 last year)  and I could find no greter butterflies on one of the rides where there had been several last year.

Lesser butterfly orchid

I did though find 3 bee orchids (in the rain inevitably).

Bee orchid