OUR NATIVE BRITISH ORCHIDS

Have you ever seen a meadow dotted with marsh orchids in flower? Do you remember grassy banks in early summer pink with the spikes of the military orchid? Have you ever watched bees visiting a bee orchid or enjoyed the fragrant scent of the butterfly orchid? These days, most people think of orchids as exotic hot-house flowers or as flowers from tropical rain-forests, not of British wild-flowers that grow on damp meadows or between the sloe bushes on chalk hillsides. To some extent, that is because many of Britain's orchid species are small-flowered and inconspicuous, of interest only to botanists and other orchid fans. However, even the conspicuous and obviously attractive of our wild orchid species are not generally known; they have become so rare that these days even dedicated ramblers are unlikely to see a lady's slipper orchid or a red helleborine, a man orchid or a spider orchid, all species which were once common in Britain.

Of the fifty orchid species known wild in the British Isles today, approximately a third are thought to be threatened and ten species are specially protected by the Wildlife and Countryside Act which makes it illegal to remove any part of the plants without a permit from the Nature Conservancy Council. Several species have populations of less than one hundred individuals. Their natural distribution has been disrupted in the last 50 years by changes in land use, including drainage of marshes and increased use of fertilizers. The rarest species must be the lady's slipper orchid (Cypripedium calceolus) which has been reduced to a single flowering individual.

Efforts to save orchid populations have included massive transplanting operations when an orchid site was going to be destroyed by building or roadworks, for example, and attempts to cultivate British and European orchids from seed and then re-establish the plants at safe sites in the wild. Both approaches have met with almost insurmountable difficulties. In an attempt to save several Early Purple Orchid (Orchis mascula) by transplanting them before the place where they grew was destroyed, the plants were carefully dug up with plenty of earth and planted in 72 other places which seemed to be suitable for the purpose because Orchis mascula also grew there. At only five of the sites were the plants able to survive and reproduce. At the 67 others they died very rapidly and finally disappeared completely. Without special laboratory techniques, it is not possible to grow orchids from seed and even when seedlings have been produced in the laboratory, it is no easy task to transplant them into the soil.

But orchids are truly fascinating plants. Their flowers are exotic and beautiful and our flora would be undoubtedly poorer without them.

All of us seem to be able to recognize an orchid flower although no two species seem to look alike. The flowers do share a common structure - six petals in two whorls of three, seen most clearly in flowers like those of the marsh helleborine (Epipactis palustris). The lowest petal of the inner whorl, the lip, is usually larger and different in shape from the remainder - formed into a large almost slipper-like pouch in Cypripedium species such as the lady's slipper orchid (Cypripedium calceolus) or flat with leafy margins and an elongated spur as in the fragrant orchid (Gymnadenia conopea) which is vanilla-scented, especially in the evenings. The inconspicuous greenish flowers of the man orchid (Aceras anthropophorum) are shaped like little dolls and the flower of the fly orchid (Ophrys insectifera) really does resemble a fly. This enormous variety of shapes, colours and perfumes and the sometimes fantastic architecture of these blooms can only be a source of wonder. Why in the course of their millions of years of evolution have these flowers developed such strange, even bizarre and grotesque forms? Why have they developed long or short spurs, trap-like or tunneled lips, such an enormous variety of fairy-tale colours? Why do their perfumes range from delicately fragrant to stinking and nauseous?

It seems to be generally accepted that the insects which pollinate orchids have played an important role in the evolution of these flower forms. It has been demonstrated that a specific kind of insect is responsible for the pollination of each orchid species: bees, wasps, ants, mosquitoes, flies or butterflies. In one group of our wild orchids, typified by the bee orchid (Ophrys apifera), the interaction of flower and insect is especially apparent. These orchid flowers are pollinated by a certain species of male bee, attracted by the orchid perfume which resembles the sexual pheromone of the female insect. The males land on the insect-like orchid flowers and attempt to mate with them; during this process they pick up the orchid pollen for transfer to the next flower that they visit.

The pollination of orchid flowers is also rather exotic. The pollen is not released as single dusty grains but is produced in packets called pollinia; they are transferred to the head of the pollinating insect where they stick up like horns in exactly the right place for pollination of the next flower. In the bee orchid, the right position for copulation is the right position for transferring pollen. In the lady's slipper, the bee is attracted by nectar inside the flower and can then only escape by squeezing through a slit where any pollinia already attached to the bee's head are scraped off onto the stigma before new pollinia are picked up at the anthers.

Orchids produce minute seeds, millions of them. The orchid fruit is a capsule which takes many months to ripen. The ripe capsules split open and the contents, thousands of seeds each only about 1 mm long, are spread by the wind. The seeds can be so tiny because they have no food reserves such as normal seeds require for germination and establishment of a seedling. Thus it is not surprising that you cannot simply pick a ripe capsule from a fruiting orchid and spread the seeds on potting compost to grow a few hundred orchid plants. These seeds can only germinate in the presence of a fungus which provides the seedling with the nutrients it requires. Some orchids seem to require one specific fungus, others will grow with any of several different fungi. The fungi grow in the soil and in the roots of orchid plants. It is a matter of chance whether the wind carries an orchid seed to a patch of soil containing the right fungus for its germination, but at least those seeds which land close to the parent plant have a good chance of meeting the appropriate fungus partner.

Some orchids such as the lady's slipper orchid (Cypripedium calceolus) seem to require the fungus only until they have germinated and produced a few green leaves. Then they can be self-sufficient like any other green photosynthesizing plant. Other orchids such as the heath spotted orchid (Dactylorhiza maculata) require contact with the fungus for the whole of their lives. They can perhaps survive for a year or two without the mycorrhiza, which is what the association of fungus and orchid root is called, but they require the partner if they are to continue to thrive and flower. There are some orchids such as the bird's nest orchid (Neottia nidus-avis) which have no chlorophyll at all in their leaves. They cannot carry out photosynthesis and are totally dependent on their mycorrhiza. Thus, survival of many kinds of orchid depends on the survival of their fungi; orchid cultivation is only possible if the fungi can be cultivated too.

We know very little about these orchid fungi. They can be seen under the microscope as coiled threads in the orchid roots and as fine threads (mycelium) growing through the soil. For purposes of orchid cultivation they have been isolated from the orchid roots and grown in culture in the laboratory. They cannot be distinguished from each other unless they can be induced to produce their fruiting bodies; on the few occasions when this has been carried out, various kinds of mushrooms or toadstools have been produced. Orchids are not the only plants which form mycorrhiza. Various of our native trees, for example, do so too. The truffle is the fruiting body of a fungus which forms mycorrhiza with oak trees and various other edible fungi are known to associate with birches, poplars or pines. We do not know what soil conditions make it possible for a certain fungus to grow. It has been suggested that every mycelium has its own patch of soil. Where two mycelia meet, they unite if they belong to the same species of fungus but if they are of different species, they repel each other. They appear to go on growing very slowly at the one site for many years.

The presence of the right fungus seems to be the factor which determines whether an orchid can grow at a certain site or not. The absence of the right fungus (which probably means the presence of another unsuitable fungus species) explains why an apparently perfect site may be free of orchids even though just across the meadow on a similar site orchids are spreading thousands of seeds in the wind.

It is not sufficient to transplant the fungus with the orchid to ensure that specimens survive. The fungus must flourish if the orchid is to survive. The fungus must win the battle for a sufficiently large patch of soil of its own before it can support an orchid. It is easy to imagine that the well-established soil fungi around a newly transplanted orchid have a marked advantage over a torn and damaged fungal mycelium which has been moved.

Do we have to watch helplessly while our native orchids continue to vanish? Fortunately the situation is not quite as bad as that. For over ten years now a project, the Sainsbury Orchid Conservation Project, has been in progress at Kew Gardens. Its aim is to propagate from seed those British and European orchids whose numbers are greatly reduced so that they can be reintroduced to the wild. Against all the odds, patient and persistent research has produced first successes. Fungi isolated from orchid roots have been used to obtain seedlings from a total of 46 British and European orchids. Some 44 species have been raised and transferred to pots in the greenhouse and five species have actually been re-established in wild habitats in England. Of these, four have already flowered and set seed. The project has attracted a great deal of interest and visitors from many countries have come to Kew to learn the new techniques which were developed for this project. The visitors have included a few dedicated British commercial orchid growers who are now using the methods developed at Kew to raise hardy native orchids for sale. Perhaps you have a corner of your garden which would be suitable for a lady's slipper orchid (Cypripedium calceolus), a pyramidal orchid (Anacamptis pyramidalis) or a fly orchid (Ophrys apifera)? If so you could indirectly support the work at Kew and help prevent the disappearance of some of these fascinating plants.

© Ann E. Wild

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