Creeping ladies tresses is mainly restricted to remnants of ancient Caledonian Forest. Flowering in late summer, it adds a splash of white to the usual greens and purples of the forest understorey.
Creeping ladies tresses is widespread, occurring in western, northern and central Europe, and eastwards to the Crimea and Caucasus. It is also present in North America, extending southwards into North Carolina. Within its range it grows from sea level to over 2,000 metres within coniferous or mixed woodland.
This is one of the few British orchids that is almost exclusive to Scotland, and is found mainly in the Highlands in remnants of Caledonian Forest in Glen Affric, Strathspey and the Cairngorms. Its present distribution does however extend from Caithness through the Highlands to southeast Scotland and into northern England. It prefers sites that are predominated by Scots pine (Pinus sylvestris) though it will grow with birch (Betula spp). It will also grow in pine plantations. It can, for example, readily be spotted in the Black Isle in the right conditions, where the plantation is mature with open areas, and has a high proportion of Scots pine.
Creeping ladies tresses is designated as a nationally scarce plant but it can be locally abundant in the northeast of Scotland. Since 1970 its national distribution has declined and it is no longer found in southwest Scotland or Orkney.
This is a perennial orchid and the only one with evergreen leaves in Britain. The rosette of leaves at the base can be seen all the year, but most easily in the winter. From the rosette a single stem sprouts in early summer upon which the flower head develops. When in full bloom the orchid can vary from 8 to 35 cm in height. The inflorescence of creeping ladies tresses has the individual flowers placed one above the other and although they are arranged in a loose spiral, the flowers tend to twist to face roughly the same direction. It is this spiral flower formation that gives rise to part of this orchid's common name, ladies tresses, as the row of small flowers is said to resemble neatly braided hair.
The flowers of all orchids, though very variable from species to species, are instantly recognisable to the lay person because of the features common to them. They all contain three outer sepals that frame the three inner petals. The two side petals are mirror images of one another while the bottom petal is quite different from the other two. The lower lip of the bottom petal of creeping ladies tresses is narrow and spout-shaped, and does not extend beyond the hood of the flower that has been created by the other two petals and the topmost sepal. The outward facing part of the three sepals and the stem are coated with hairs that are easily seen by the naked eye. This is one of the main features that distinguishes creeping ladies tresses from the other three species of ladies tresses in Britain.
Being mainly restricted to the Caledonian Forest, creeping ladies tresses is usually found growing in pine needle litter amongst mosses ,heathers (Calluna vulgaris, Erica cinerea), blaeberries (Vaccinium myrtillus) and other common understorey plants. The flowering season of this species is much later than most other British orchids and it is speculated that this may have evolved to coincide with the flowering of bell heather (E. cinerea) to ensure that there is an abundance of potential pollinators in the local area. They do not like to be too shaded and are usually found in open stands or of trees at the fringes of the forest. They are also seen growing out in the open surrounded by only heather, although some pines will always be nearby. They are also occasionally found in mature pine plantations in open glades, where Scots pine is the dominant tree. Where they do occur in plantations they are numerous and successful.
Blossoming from mid July to late August, the flowers at the base of the inflorescence open first. The three outer protective light green sepals open out to reveal the creamy-white delicate beauty of the flower and this lets the sweet scent take to the air to attract insects.
In orchids the male and female reproductive organs are highly modified and are fused together, unlike most other plant families where the sex organs are separate. Looking carefully into the flower, a touch of orange pollen can be spotted on the tip of the anther, the organ that delivers pollen to visiting insects. This is the male part of the flower, while the female part, the stigma, is situated just below the anther. The stigma receives the packet of pollen which is then transferred to the ovary where fertilisation occurs. To perpetuate their genetic mix, orchids have developed various methods to increase the chances of cross pollination between individuals of the same species, rather than allow self pollination. For example some orchids have evolved a system of using a natural glue to stick a packet of pollen to a visiting insect. As the insect moves on, the glue dries and causes the pollen packet to be set at a specific angle to ensure that it is more likely to come in contact with the stigma of the next flower visited. The specific method of pollen transfer from flower to flower in creeping ladies tresses is unknown. Unlike some other Scottish orchids, this species does not cross pollinate with any other species and there are no known hybrids.
After pollination and fertilisation the seeds develop in the ovary. The ripe seed capsule has six segments of which three contain many thousands of tiny dust-like seeds. They are released when the capsule dries and splits longitudinally, allowing the wind to carry them long distances. This strategy ensures that the numerous seeds are dispersed over a wide area and that one or two may therefore land in a site which has the right conditions for the seed to germinate.
As well as reproducing sexually by producing seeds, creeping ladies tresses can propagate itself vegetatively via runners that spread through the pine needle litter, thus giving rise to the first part of its common name. The advantage to the orchid of vegetative reproduction is that it can colonise an area more rapidly than if it were growing from seed. It can often take up to three or four years after germination for the orchid to flower. The clusters of creeping ladies tresses that can be seen in amongst the ground vegetation of the Caledonian Forest are characteristic of this form of reproduction and it is the only orchid in Scotland with a creeping habit. Groups of these orchids range in size from 5 to 25 individuals.
All orchids demonstrate one of the closest symbiotic relationships known in the plant kingdom, and creeping ladies tresses is no exception. A symbiotic partnership means that both parties benefit from the association, without any detrimental effect to one another. Orchids have a very intimate relationship with specific fungi and in fact they cannot grow without their fungal partner. The fungus actually lives inside the root cells of the orchid and this close partnership results in a dual organism known as a mycorrhiza. Within the root the fungus is provided with an ideal growing environment, devoid of competition and it is thought that some vitamins are provided by the orchid. Part of the fungus penetrates the root wall and has contact with the surrounding soil. It can then take up nutrients, such as cellulose and other carbon compounds, and break them down to a soluble form that can be used by the orchid.
The tiny seed of the orchid can begin germination in the absence of an associated fungus. The process is only completed however, once an appropriate fungus has infected the embryo. The association is essential at this point as the orchid cannot absorb nutrients from the soil on its own and the tiny seed contains no food reserves to sustain growth. Once the orchid matures there are varying degrees of reliance upon the mycorrhizal partnership. Some species of orchid lack chlorophyll and are consequently completely dependent upon the partnership throughout their lives. Creeping ladies tresses can germinate in the presence of one of two fungi, either Rhizoctonia goodyera-repentis or R. lanuginosa , but the subsequent dependence on the fungus is unknown.
The main insect associated with pollination of creeping ladies tresses is thought to be the bumble bee ( Bombus lucorum ). In return for being the carrier of pollen between flowers, thus allowing the important process of cross pollination to occur, the bumble bee receives energy in the form of nectar. Though creeping ladies tresses can reproduce by vegetative means, it is still very important to reproduce sexually to increase the genetic mix. This means there is a greater variability between individual plants which makes the species more adaptable to change.
Creeping ladies tresses is susceptible to damage from overgrazing by deer and sheep. However the simple measure of excluding deer will allow this species to recover, as can be seen in the Coille Ruigh exclosure in Glen Affric. Current regeneration measures for the native pinewood remnants throughout the Highlands of Scotland should ensure that this beautiful and delicate species continues to thrive and flourish here.
Alan Watson Featherstone