Broad-leaved helleborine, pollinated by wasps.

We found a population of about 30 broad-leaved helleborines Epipactis helleborine beside the Deerness Valley walk, a disused railway track that has been converted into a pleasant route for walkers and cyclists. 

This is an orchid that thrives on woodland edges, in dappled shade. It's pollinated by common wasps Vespula vulgaris, but this was the first time I have seen the pollinators in action.

The flowers emit a scent that attracts the insects, which have short tongues, so they have to push their head right into the flower to reach a pool of nectar. When they do this the orchid's pollinia, which contain all their pollen, stick to the wasp's face. In the photographs above and below (rather blurred, because the light was poor) you can see a wasp arriving after visiting another plant, carrying the white pollinia on its head, ready to pollinate the flower.

Below, you can see a wasp leaving, taking the sticky pollinia with it, attached to its face.

Click here for a very good YouTube video, by Jean Claessens, of the whole process

Orchids on the Durham coast

Durham's magnesian limestone grassland is famous for its orchids. Yesterday, when we were walking along the coast near Hawthorn Dene there was a sensational display, in the hay meadow at the mouth of the dene itself and even more so in the thin soils around the old quarry. 

There were many hundreds of spotted orchids and scores of pyramidal and fragrant orchids. There were also plenty of twayblades, but it's hard to estimate their numbers because their green colour makes them easy to overlook. 

I think this was the best orchid display that I can remember here.

Fragrant orchid

Pyramidal orchid

An albino common spotted orchid

Common spotted orchid

Twayblade orchid

This is the area around the quarry with the highest density of orchids, growing in a thin veneer of soil over limestone. Other species in flower here included centaury and yellow-wort, greater knapweed and carpets of bird's-foot trefoil.

Bird's nest orchid

Thursday's Guardian Country Diary is about this strange plant, bird's nest orchid Neottia nidus-avis.

I've only found it on three occasions. 

The first was when I was 18, in my final year at secondary school and studying for university entrance examinations. As the only pupil taking botany A level ( now a long-extinct qualification) I was lucky to be taught by Bill Jackson, a teacher who had done an M.Sc. with the noted botanist Herbert Baker. Bill was a good field botanist who gave me a lot of encouragement and suggested that I should do a field project on orchids in Sussex, so I spent many days when I should have been at school  out on the South Downs, looking for these exotic plants. 

On one memorable day I found bird's nest orchid in a beech wood and photographed it. A few months later, when I went for the university interview, I took the pictures with me. My interviewer had never seen the plant and we spent almost the whole time talking about it. Finding that orchid was most probably a significant factor in being offered a place at university. 

I was thirty years before I found the plant again, in a hazel coppice in a wooded valley in Co. Durham. This time it was a pretty miserable specimen, but it was a real delight to see it again. Every year after that we searched the area in July, hoping that it would reappear, without success until a few weeks ago.

I was tipped off that something that sounded very much like bird's nest orchid had been seen there. We searched the original site in the hazel coppice again, but there was no sign of it. Then, when we turned for home, disappointed, my wife spotted this magnificent specimen in an unlikely place ...

....... growing amongst widely spaced hazels, amongst hay meadow species like meadow cranesbill and pignut.

This is an unlikely plant association because bird's nest orchid is usually found in woodland in deep shade, especially in beech woods where there is very little ground flora.

The plant has no chlorophyll, so has no need of sunlight. Its nutrition depends entirely on a fungus called Sebacina that in turn forms a symbiotic, mycorrhizal association with surrounding tree roots. The fungus gets its sugars from the trees and it in turn enhances the tree roots' capacity to absorb minerals from the soil. The orchid contributes nothing to the relationship, merely living off of the fungus.

The flowers produce a vast number of dust-like  seeds but their chances of landing near the essential fungus are slim. After germination the plant takes a decade to reach flowering size and only flowers once before dying, although it is said that its rudimentary root system, which resembles an underground bird nest, can produce further plants in subsequent years. So we'll certainly be going back next year to see if that is the case.

Common helleborine

Broad-leaved helleborine Epipactis helleborine is our commonest helleborine species but it's muted colours make it easy to overlook when it's growing amongst tall vegetation. This fine specimen was growing on a bank amongst long grasses on the outskirts of Durham city.

This orchid seems to be spreading quite nicely around Durham city - it's now well-established in numerous places in Durham University Botanic Garden where the gardeners carefully mow around it. I've also seen it in the grounds of several colleges, but there the plant is often less fortunate and tends to be mown when the grass is cut, after the daffodil foliage withers, and never reaches flowering size.

Magnificent Marsh Orchids.... or spotted orchids .... or hybrids?

Well, actually I'm not sure what these are, exactly. They were part of a swarm of hybrids between marsh orchids and common spotted orchids, growing beside the pond on Durham University's Mountjoy site. Whatever their precise identity, they are magnificent specimens. I have noticed that whenever these hybrid swarms occur you always get a few very robust, very floriferous specimens, probably displaying hybrid vigour, alongside many more that are much weaker plants.... and, quite often, a few albinos like the one on the left.

Sun, Sand and Orchids

Today's Guardian Country Diary describes a recent visit to the seaside at Cleethorpes. If you walk on past the pier with all its attractions, at the far end of the promenade, beyond the leisure centre and just under the sea wall near the miniature railway, you'll reach Cleethorpes Local Nature reserve. 

It's a long expanse of sand dunes, between the sea wall and the saltmarsh on the edge of the river Humber, and it hosts a fabulous display of southern marsh orchids that were in full bloom at the end of May.

There are some magnificent specimens that....

.... are packed together so densely in places that you need to be very careful where you put your feet.

While we were there I repeated Darwin's experiment for extracting the pollinia from an orchid flower, described in his book Fertilisation of Orchids, which I described in a recent post on early purple orchids. The pollinia are whole stamens that butterflies carry away in their entirety when they poke their proboscis into a nectar spur at the rear of the individual orchid flower. Darwin described how you could extract a pollinium, which is sticky at its base, by poking a sharp pencil point into the nectar spur. The paired pollinia are located where those two dark club-shaped structures are in the hood of the flower.

I didn't have a pencil so I poked this fine twig in instead - and out it came with a pollinium attached.

Darwin actually counted and calculated the number of pollen grains in one of these pollinia: there are enough to fertilise over 120,000 seeds. The survival chances of these tiny wind-born seeds, which you can see by clicking here, are minute.

The Cats' Pee Orchid's Life of Deceit

We found a fine display of early purple orchids blooming on the cliff tops south of Seaham, along the Durham coast, today. They're beautiful flowers to look at but less attractive when you smell them, as they emit a strong aroma of cat's urine which is generally repugnant to people but attractive to bees........ which are in for a disappointment when they visit these flowers.

Charles Darwin spent many years studying orchids and was intrigued by their elaborate flowers and complicated pollination arrangements. In his seminal book in the subject, The Various Contrivances by which Orchids are Fertilised by Insects, first published in 1862 and which you can download here, he noted that although the flowers have a well developed nectar spur they don't produce any nectar. Bees that visit are duped into exploring one or two flowers in an inflorescence but soon leave when they find no sweet reward - but by then they've performed the essential pollination service that the plant requires.

This is Darwin's detailed dissection of an early purple orchid flower. The two important features to note are the hollow nectar spur in the uppermost illustration, which shows a longitudinal section of the flower, and the club-shaped structure in the centre, which is the pollinium containing the pollen grains. 


Try as he might, Darwin could find no trace of nectar in the nectar spur and was reduced to suggesting that if visiting bees did extract any reward from the flower it could only have been by piercing the floral tissues with their proboscis, which has never been proved to be the case. He concluded that the basis of pollinator visits was deceit on the part of the plant, that relied on naive, newly-emerged bees in spring making exploratory visits to any flower that might contain a food source.  


The other part of the flower that intrigued Darwin was the pollinium - the male stamen that is carried away in its entirety when a bee probes for nectar and the pollinium sticks to its tongue (click here for a picture of a pollinium-encumbered bee visiting an orchid). 

Each flower has a pair of pollinia - they're the two dark, club-shaped structures under the hooded petal in the flower above. When they're carried away by a bee they bend forward within about a minute, so they're well positioned to make contact with the stigma of the next orchid flower it visits.

In his book Darwin demonstrated rather neatly how you could mimic the whole process by poking a sharpened pencil into the flower. Try this - it really works. When you withdraw the pencil with the pollinia attached their stalks dry out and they slowly bend forwards. Incidentally, the ever-meticulous Darwin dissected, counted and estimated the number of pollen grains in a single pollinium - a staggering 122,400.

This orchid's deceitful pollination technique is only partially successful because bees are smart and after visiting a couple of flowers look elsewhere for an energy reward. Darwin's work was followed up in the 1990s by Dr. L.A. Nilsson at the University of Uppsala who showed that bees would visit more flowers on an inflorescence if those empty nectar spurs we filled with artificial nectar. 

Nilsson noted that early purple orchids only produce a few seed pods, developing from the first few flowers to open at the bottom of the inflorescence. The rest almost always remain unfertilised, although 80% of them could set seed if they were hand-pollinated. The first bees of spring may be naive but they learn fast and if they don't find the reward they are looking for they soon ignore that attractive scent of cats' pee and take their pollination services elsewhere, leaving many early purple orchid flowers unpollinated. 

Fortunately the seed production  from a single  pollinated flower is quite large  ..........Darwin counted 6200 seeds in a single capsule of spotted orchid and this species' seed production would be similar.... so early purple orchids manage to survive on deceit.

Pink Pyramids

Port Logan, on the Rhins of Galloway peninsula, is sandy bay backed by a stony beach and sand dunes, that takes the full force of the wind and weather sweeping in from the North Channel and Atlantic beyond.

Not, maybe, the kind of place you'd choose to stop on a wet and windy day, but we noticed some interesting-looking flowers in the dunes as we drove by, so stopped to investigate - and we were glad that we did.

When we reached the beach this ringed plover flew off and settled a few yards away, obviously trying to distract our attention....

... and we soon discovered why ..... this wonderfully camouflaged clutch of eggs, laid in a depression in the sand.

But it was the pyramidal orchids - dozens of them - that had first attracted our attention....

Most were the typical deep pink-flowered form but ....

... this one stood out - a much paler pink-flowered plant.

On this coast the weather changes rapidly and within a few minutes the sun broke through, coaxing out the bumblebees to feed on the sea bindweed blooms.

Unlike the climbing bindweed species that plague gardens, this species stays close to the ground, sheltered from the drying wind and conserving water in its succulent, heart-shaped  leaves.

Orchids Do It Differently

Most flowers discretely dust their pollen on visiting insects, but orchids go the whole hog and glue their entire stamens to their visitors. The paired stamens – known as pollinia in orchids - sit inside the hooded upper petal (top photograph) and the nectar supply is hidden deep within the flower, so even long-tongued bees like the one in the second photograph must force their head in to reach it. And that’s when they make contact with the base of the pollinia, which become glued to their head, so when the bee leaves it carries the pollinia with it. By the time it’s reached the next plant each pollinium has split open, exposing pollen that’s dusted on to the stigma of the receiving plant. You can see the white, ruptured pollinia just below the antenna on the face of the bee in the third picture, and the same area enlarged on the final image. Bees are often irritated by having these objects glued to their head and sometimes try to comb them off, but seldom succeed. Why do orchids operate in this way? Well each individual orchid flower can produce hundreds – sometimes thousands – of ovules and it needs a comparable number of pollen grains to ensure that they’ll all be fertilised and develop into seeds – despatching a whole stamen’s worth of pollen in one go, glued to an insect, does the trick very nicely.