Helleborines (Epipactis) in Fruit

Over the last few days I made a couple of trips to the Chilterns and one to a wood near Solihull to look for helleborines in fruit.  I found four species, dune, broad-leaved, green-flowered and violet.

I measured the fruit set success by counting the number of seed pods compared to the number of bracts in the inflorescence.  

	Fruit set	Fruit set
		Sample size
Dune	89%	9
Broad-leaved	89%	3
Violet	37%	1
Green-flowered	72%	2

Both dune and especially green-flowered, are self-fertilising.   Green flowered did not open out at flowering time, but nevertheless set fruit.  High rates of fruit set are therefore to be expected.  With green-flowered some of the flowers simply blackened and withered.

The fruit set % for violet helleborine is again to be expected; it is pollinated by bees and wasps, but it grows in deep shade, where wasps are not commonplace.  Higher fruit set rates are commonplace in mainland Europe though.   By contrast broad-leaved helleborine seems to attract every wasp from a distance around and that leads to a high fruit set.

Tree Wasp Pollinating Broad-leaved Helleborine in early August

These though were not random samples - I was attracted to the biggest and boldest in the case of broad-leaved helleborines, and later I did find a few plants where spikes had no seed pods.

Dune Helleborine

Green-flowered Helleborine

Broad-leaved Helleborine

Violet Helleborine

I then took averages of the seed pod width and length for each species and the angle that the seed pods are held from the vertical (facing up then less than 90°, facing down greater than 90°.   I finally brought a few seeds of each home and got an average for length and width.

	Seed pod		Angle	Ratio	Seed		Pod L;W ratio
	L mm	W mm	to Stem °	L:W	L mm	W mm	over Seed L
Dune	10.3	6.8	94	1.41	1.11	0.24	1.26
Broad-leaved	12.4	7.6	126	1.63	1.08	0.26	1.51
Violet	11.3	6.8	118	1.67	1.29	0.20	1.28
Green-flowered	10.2	6.7	157	1.54	1.06	0.19	1.46

The angle held to the stem is interesting, and is helpful in discriminating, as too is that final calculation - the pod length:width ratio divided by seed length.   This together with the angle to the stem, and leaf colour and dimensions should enable a helleborine to be identified to species level.  Of course though my sample size was far from statistically sound.

For the broad-leaved helleborines I also  worked out pod dimensions by the position on the inflorescence.

	Average	Average	Average	L:W
	Angle	Length mm	Width mm
Bottom Quartile	137	14.1	8.1	1.73
Lower Middle Quartile	123	13.0	7.7	1.69
Upper Middle Quartile	134	12.2	7.7	1.58
Top Quartile	113	10.6	6.9	1.55

The seed pods became smaller and less narrow moving up the stem, and were kept nearer to 90°.   I did not have enough measurements from the other three species but violet did not seem to behave in the same way.

I then ran out of things to measure!