Pollinators of the Early-purple Orchid
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Observations on the frequency with which the flowers of Early-purple Orchids (Orchis mascula) set fruit were presented and discussed at recent HOS meetings and are included in an article published in the April 2013 Journal of the Hardy Orchid Society. When compared with the classical view of O. mascula pollination, the studied Norfolk populations were very efficiently pollinated, achieving frequencies as high as 100% for individual plants and 84% for population averages. One possible explanation is that the habitats sampled retained large numbers of pollinating insects due to the presence of companion flowers that, unlike the Early-purple Orchids, do offer a nectar reward. Bluebell (Hyacinthoides non-scripta) and Bugle (Ajuga reptans) appeared to be significant in this regard. This would be an example of an established concept referred to as the "Magnet Species Effect".
It would be interesting to collect more data from a variety of different habitats with records for the presence of companion flower species, observations of insect visitors and later, counts of fruit set frequencies. Populations lacking companion flowers are as interesting as those with them! An outline recording form is provided to assist anyone interested in checking out Early-purple Orchids. For larger populations a sample of 30 plants randomly checked for fruit set frequency would be ideal but any records will be of interest. When randomly selecting plants it is important not to ignore spikes with no or few set fruits.
I find it easiest to run fingers up the spike from the bottom whilst counting fruits as it helps to keep track of where you have got to. It is important to count the total number of flowers that were present i.e. both set fruits and flower remnants where no fruit is set. Whilst not essential, noting the positions of the set fruits by giving them a number from the bottom of the spike would be interesting in the context of the oft mentioned preferential pollination of the bottom flowers.
Observations should be sent to Mike Gasson (address on inside cover of JHOS) or by e-mail to email@example.com.