Category Archives: Orchids

Fly Orchids in the Avon Gorge

FlyOrchid

Fly Orchid (Ophrys insectifera) is in flower currently in the Avon Gorge. To see the most accessible plants, head north on the towpath on the west side of the gorge, to an area of rock falls about half a mile north of the Suspension Bridge. I counted 10 plants in flower today by the fence at the bottom of the rocky slopes (see map & photo below). Here they grow in the open, in limestone grassland, but at other sites Fly Orchids occur in woodland.

Fly Orchid is a scarce plant around Bristol. The Avon Gorge is the only site in close proximity to the city: the location I visited on the North Somerset side is the most well-known, although Fly Orchid has also been found occasionally on the Bristol side. Elsewhere in the region, there is a cluster of sites in the Avon valley southeast of Bath, including Browns Folly and Avoncliff. There are several other sites farther south and east of here into Wiltshire and east Somerset, including Cleaves Wood near Wellow, Morgans Hill near Devizes, and a grassy bank on the north side of the A303 near Wincanton. Elsewhere in Somerset, Fly Orchid is only found on cliffs near Blue Anchor. Its stronghold is in the Cotswolds, with around 10 sites in the Stroud area and others southeast of Cheltenham. Although it formerly occurred in the Wye Valley, it is now extinct there.

FlyOrchidSite

Pollination is carried out by male digger wasps of the genus Argogorytes, which are attracted to the flowers by a pheromone; they mistake the flower for a female digger wasp and attempt to mate with it. In doing so, the orchid’s pollen sacs attach to the wasp, and are then transported to the next orchid the wasp visits. The Avon Gorge Fly Orchids are of particular note, as in the past, this process went a little awry and hybridisation occurred with Bee Orchid (Ophrys apifera): when these hybrids were first discovered here, in 1968, they were new to science. Hybrids are not known from the Avon Gorge currently, but they are present at the Wincanton site. Hybridisation has also occurred in Kent with Early Spider Orchid (Ophrys sphegodes).

Autumn Ladies-tresses on Bristol Downs

There are a few flowering plants that wait till the end of the summer before flowering, and Autumn Ladies-tresses (Spiranthes spiralis) is one of them, never flowering before August and continuing well into September. This is probably the least conspicuous of the orchids which are found in the Bristol area, typically only reaching about ten centimetres tall. The photos below show the way in which the tiny flowers spiral around the stem, a feature reflected in its scientific name.

ALT2 ALT1

I visited the colony on Bristol Downs today, and counted at least 87 plants – although among these were many which weren’t in full flower yet, which I only noticed when I was on my knees next to plants which were in flower, so as I will have no doubt missed other similar individuals, I’m confident the total population here is well into three figures.

Here’s the location: right next to the circular road which runs around the Downs.

Autumn Ladies-tresses is a plant of very nutrient-poor limestone and chalk grassland. In most locations, sheep do the work of keeping the habitat conditions right; on the Downs, in the absence of sheep, the grassland has to be managed by mowing and raking off the cuttings. On the side of the colony closest to the road, the soil has been badly eroded by runners; fences have been erected to encourage people off of this part of the site, in the hope that it will regenerate.

The Downs as a whole are a bit of a curate’s egg botanically, even if you discount the areas which are formally set aside for sports. Although it is certainly the largest area of limestone grassland around Bristol until you reach the Mendips and Cotswolds, that doesn’t necessarily mean it’s good-quality limestone grassland throughout. Some areas are good – I found a few Harebells (Campanula rotundifolia) growing in another spot today, for example – and the stone workings on the southeast side have some botanical interest, as does the area around the observatory. However, other parts are quite species-poor. With the right management to reduce the nutrient levels, though, the Downs could certainly become a lot richer, and complement their neighbour the Avon Gorge.

Green-flowered Helleborines

Ashton Court, a walled estate just to the west of Bristol is famous for hosting the Bristol International Balloon Fiesta, but it has a botanical claim to fame too: the only accessible Green-flowered Helleborines (Epipactis phyllanthes) in the Bristol area grow here, in a dark wooded part of the estate called Clarken Combe, just a short hop over the wall from a layby on the B3128. I paid the site a very quick visit last weekend and was surprised to find many more plants than I’ve seen here previously, although all were still in bud. This weekend, however, several were flowering: mostly each plant had just a single stem, but one plant had a cluster of nine: here is a photo, and a close-up of some of the individual flowers.

 GFH1  GFH2

These plants have an interesting history. Originally found in 1985, they were thought to be Narrow-lipped Helleborines (Epipactis leptochila), a scarce species of limestone beechwoods. They were listed as this species in the Flora of the Bristol Region, published in 2000, and this identification remained unchallenged until fairly recently. I paid the site a visit in late summer 2011, not really knowing any more than to look in the woodlands at Clarken Combe, I narrowed my search by looking under beech trees, and eventually found three helleborine plants, but they were past flowering, so I visited again in 2012 with Martyn Hall, who took some photos. Still none the wiser as to the plants’ true identity, I posted these to the orchid thread at Birdforum. Midlands-based orchid expert Sean Cole posted a reply, asking whether I was sure the plants were Narrow-lipped Helleborines, as they looked to him more like Green-flowered. That afternoon, Richard Mielcarek and I went back to Clarken Combe, gave the plants a very close look, and confirmed that, just as Sean thought, they were Green-flowered Helleborines.

Part of the reason for the confusion is that back in the 1980s, knowledge about the variability of the Epipactis helleborines, and which identification features are most reliable, was still developing: nevertheless, the plants had been visited by many knowledgeable botanists since, and so it’s surprising that it took so long for them to be re-identified.

Green-flowered Helleborine occurs in several varieties (forms of characteristic appearance caused by small genetic differences). The Clarken Combe flowers open quite widely, seem to have a clear distinction between the ‘cup’ (hypochile) and the ‘lip’ (epichile) and in some, the lip is bent back under the cup, whereas in others it is not, and then appears quite long and pointy. As I understand it, this points to them being of the variety known as ‘vectensis’, but I’d be interested in views from others with more knowledge of this subject. The pointy lower lip and the fact that the flowers open widely may be one of the reasons why the plants were originally thought to be Narrow-lipped Helleborines. However, the hypochile of Narrow-lipped Helleborine is filled with a sticky dark purplish liquid, not present in the Ashton Court plants, and the lip of Narrow-lipped is even longer and thinner. There are several other features visible with a hand-lens, which Richard and I checked last year to satisfy ourselves that our re-identification was correct.

In a local context, Green-flowered is only marginally less rare than Narrow-lipped. Narrow-lipped’s nearest population is in the woodlands at the top of Cheddar Gorge; Green-flowered occurred in the past on the towpath below Leigh Woods, but has not been seen here for many years, and only occurs at one other site, a private garden near Stowey. Further north, on the Cotswolds, both species have strong populations, and Green-flowered also occurs at several sites in Wiltshire. Nationally, Narrow-lipped is the scarcer of the two, and its populations are in decline, whereas Green-flowered is if anything on the increase.

Here is a map showing the location of the plants. If you visit, please take great care where you put your feet, as some of the plants are quite small. There are differing views among botanists about the levels of secrecy that should surround locations of scarce plants, and in particular orchids. One orchid site on the edge of Bristol suffered from theft of a very rare species this year, so concerns are very valid. Fortunately, I don’t have to make the decision over the Ashton Court plants, as Bristol City Council have publicised them for many years as one of the features of the site (albeit unwittingly as the wrong species).

Kingsweston Down

I visited Kingsweston Down yesterday: this is the large area of limestone grassland that runs along the top of the ridge which extends southwest from the Blaise Castle estate. Both the north and south sides of the ridge are covered in woodland, so the whole area is quite sheltered. In some places the grassland is nothing to write home about, but there are some quite extensive patches which are either dominated by Upright Brome (Bromus erectus) or rich in herb species, or both.

One of the most abundant herbs at the site is Yellow-rattle (Rhinanthus minor), in the left-hand photo below. This is a classic indicator of good-quality grassland: it’s a common species of old hay meadows, for example. Yellow-rattle is partially parasitic on the roots of grasses. As you can see in the photo, after flowering the calyx which surrounded the flower inflates: inside, the seeds which develop are loose, and when the plant is blown by the wind, they make a rattling noise inside, hence the plant’s name.

 Yellow-rattle  Common Spotted Orchid

The right-hand photo is of a Common Spotted Orchid (Dactylorhiza fuchsii), one of four growing together in one part of the site. Common Spotted Orchid is our commonest orchid, and colonises new sites readily, liking both grassland and woodland edges, so isn’t particularly indicative of a good quality site, unlike many other orchid species. This individual is a little on the pale side, prompting thoughts of the rarer Heath Spotted Orchid (Dactylorhiza maculata), but the shape of the lower lip, with three more or less equal-sized lobes confirms that this is Common Spotted.

Avon Wildlife Trust previously managed the site, and then it was in better condition, with shorter grassland supporting species such as Restharrow (Ononis repens) and Harebell (Campanula rotundifolium). Today the grass here is quite long, and these species are probably crowded out.

The site can be accessed either from the Blaise Castle estate itself, or from footpaths leading in from Coombe Dingle to the south. Here’s a map:

Bird’s-nest Orchids in Lower Woods

Vic Savery kindly sent me this excellent photo of a Bird’s-nest Orchid (Neottia nidus-avis), one of a group of six he found today in Lower Woods, near Wickwar. The plants were in either Gibbons Trench or Horwood Trench, two paths which run west from the main north-south ride (see the reserve map here). Bird’s-nest Orchid is found in several scattered woodland sites around Bristol, usually in small colonies like the one Vic found today. The situation is much the same in Somerset and Wiltshire, but it becomes more common in the Cotswolds, the Forest of Dean and the Wye Valley.

birds nest orchid 9
Bird’s-nest Orchid, 27 May 2013, Lower Woods, Gloucestershire, Vic Savery (naturenutz.net)

Bird’s-nest Orchid obtains its nutrients from a species of Sebacina fungus, which lives in the root system of the orchid and in turn receives its nutrients from nearby tree roots, The relationship between the fungus and tree is a two-way partnership: the fungus passes minerals back to the tree. The orchid however, gets a nutritional free ride. In many sites, the host tree is Beech (Fagus sylvatica), although in Lower Woods, it is presumably Hazel (Corylus avellana). Anyway, because of all this, Bird’s-nest Orchid doesn’t need any of the green photosynthetic chlorophyll molecule, hence its characterstic pale brown colour. No other similar-looking British woodland plant species is at its flowering peak at this time of year: Toothwort (Lathraea squamaria) is well past its best, and Yellow Bird’s-nest (Monotropa hypopitys) is still underground.

For more of Vic’s photos, take a look at his website.