Hybrid Lady x Monkey orchids

In 1997/1998 we first discovered an orchid leaf rosette that was much more vigorous than a normal Monkey orchid so we watched it with interest. In 2002 it flowered for the first time and, to our surprise, we discovered that it was a Lady orchid (Orchis purpurea).

In subsequent years we monitored several more Lady orchid leaf rosettes and a few others that seemed slightly different but it wasn’t until 2006 when one flowered that we discovered that we had something really quite different and very exciting – a plant that had the stature of a Lady orchid but the flower colour (and to a degree shape) of a Monkey orchid. We realised quite quickly that it must be a hybrid between the 2 species, the plants having the following mix of features:

• the lip shape is like Monkey orchid but the legs are thicker
• the hood is strongly speckled (like Lady orchid) with a deep purple colour (like the lip colour of a Monkey orchid). The hood of both Monkey and Military (Orchis militaris) orchids is most often very pale (almost white) with streaks of purple scattered sparsely across the surface
• flowering period was 5 days after the Lady orchids and 1 week before the bulk of the Monkey orchids
• the hybrids are much larger and more vigorous than the normal Monkey orchid and much closer in form to the Lady orchid
• flowers open from the bottom up as in Lady orchid – not top down like the Monkey orchid
• foliage is lush and bushy, like the Lady orchid but is a grey-green, like the Monkey orchid

On discovering that we had potential hybrids I contacted BBOWT, the site owners, and we agreed to get expert advice before going public with anything. Also, the amount of damage caused by visitors to the slope (trampling of orchids and erosion) on a normal year is quite high so for the good of the site and the other plants we decided not to advertise the hybrids in any way that year.

Scientific work

Very early on I took advice from a few trusted friends in the orchid world and Bill Temple (of the Hardy Orchid Society) suggested I contact Richard Bateman from the Natural History Museum. He is one of the leading authorities on European terrestrial orchids and on hearing our news got in touch with Mike Fay from Kew Gardens and put together a team to visit the site.

Richard concentrated on pollen and morphological analysis, while Mike took samples from each plant to test the DNA.

There have been quite a few papers published on the hybrids – here are a few:

• Richard M. Bateman, Rhian J. Smith and Michael F. Fay (2008) Morphometric and population genetic analyses elucidate the origin, evolutionary significance and conservation implications of Orchis x angusticruris (O.purpurea x O.simia), a hybrid orchid new to Britain. Botanical Journal of the Linnean Society, 2008, 157, 687-711.
• Bateman, R. (2010) Where Does Orchid Conservation End and Gardening Begin. Journal of the Hardy Orchid Society. Vol. 7, No. 4 (58) October 2010

Historical context

Orchid hybrids are not that uncommon in the wild, where closely related species grow together. However it is very rare to find a hybrid between 2 rare species of orchid and this was the first natural hybrid between the 2 species recorded in the UK. However, in Europe the 2 species grow together more commonly and just a quick Google search for “Orchis simia x purpurea” will yield a few websites with photographs of French specimens.

Today we just have isolated colonies of Lady, Monkey & Military orchids and each one has gone through population collapses that have reduced the genetic variability massively. Monkey orchids on Hartslock were found to be very very closely related and we know from our herbarium specimen research that collectors seemed to favour the taller, more beautiful plants and these would have been removed and prevented from reproducing and passing on their genes. In the past the 3 species were never ‘common’ but they were much commoner and it is not a big stretch of the imagination to suggest that they must have had overlapping ranges as they have similar habitat requirements.

So, it is my theory that in the past the 3 species grew in colonies scattered all along the south Chilterns, with Monkey orchid favouring the western end, Military favouring the eastern end and Lady scattered amongst them. They probably hybridised much more frequently and the resulting plants were harder to split into 3 distinct species. Far from being a problem, the new Lady x Monkey hybrids might actually be returning the population to a more natural state where occasional mixing of genes between the species was normal.

Should we be worried about the hybrids?

Many people have asked if we are worried about the appearance of hybrids and the potential for them to cross and recross with the Monkey orchids causing genetic pollution and over time wiping out the ‘pure’ Monkey orchids. They argue that not only would the Hartslock strain of Monkey orchid (smaller with pale flowers) not exist but whatever characteristics the plants have that enables them to survive on Hartslock might be lost and in successive generations a drought or cold snap might actually wipe out all the plants.

Personally, I don’t think we have enough information yet to know if this is a problem and we should just see how things go. If the hybrids do re-cross into the Monkey population the resulting injection of genes might actually do the population good. Remember, we know that they have gone through a very severe genetic bottleneck and from a genetic diversity viewpoint the plants are worryingly similar. Also, the plants we have on site now are very small when compared to some of the plants we have seen in herbarium collections and so even on the morphological side it is logical to assume that the colony should have much greater variability.