Orchids have a reputation for being rare, yet there are 28 species native to Ireland. However, their habitats are now under threat, writes Anthony King.
Orchids, admired for their beauty and esteemed for their rarity, are becoming ever rarer in modern Ireland.
Though you might associate them with the lush tropics, there are 28 species of orchid in Ireland. One-third of them are now considered rare or endangered.
Karl Duffy at Trinity College Dublin has been studying four of our rarest orchids for his PhD thesis. "We knew they were rare but we didn't know what was going on with them," he explains.
Orchids use insects to transfer pollen from one flower to another, and many of their most eye-catching flowers evolved to lure insects and daub them with pollen.
Duffy was interested in whether a decline in populations of important pollinators such as bees has in turn reduced orchid pollination.
As project supervisor Dr Jane Stout of Trinity's botany department explains, a rare plant might attract fewer pollinators which might mean it becomes rarer. But results so far suggest habitat destruction and habitat change remain the greatest threats facing our native orchids.
Duffy points to the bog orchid, sword-leaf helleborine and small white orchid as having undergone substantial declines. The bog orchid suffers with the destruction of bogs. The small white orchid, a plant pollinated by night-flying moths, has probably been hit by grazing and improvement of pastures.
The sword-leaved helleborine is among the most striking Irish orchid, with up to 40 white flowers, each with an orange dash. "It's my favourite species," says Duffy.
"It is a showy plant that doesn't contain nectar and doesn't offer anything to the bee. Bees think the big orange blob on the flower is pollen; it even has texture like pollen. But it's a trick the plants use to attract naïve bees." Such deceptions are rife in the orchid world.
Orchids make difficult subjects and determining a population's status can be tricky. Many species are scattered in small groups and spend most of the year as nondescript buds. Some can survive for five years as underground tubers, filching nutrients from fungal "partners".
Tapping soil fungi for food means orchids can prosper in low nutrient environments. But fertiliser is harmful to most species.
Darach Lupton of Trinity has just completed a PhD on Irish Lady's-tresses, a distinctive orchid with a spike of white, tubular flowers. Growing in damp habitats, its colonies are susceptible to drainage and nutrient enrichment. "Increased nitrogen on the landscape doesn't suit orchids: they won't tolerate it and it boosts the growth of invasive or competitive species," says Lupton.
Though widespread in North America, Irish Lady's-tresses is one of Europe's rarest orchids, with just a few populations in western Scotland and Ireland.
There was controversy over whether it was introduced to Ireland, but Lupton found genetic evidence to support its native status. "It is sufficiently divergent from North American specimens to suggest it has been here a long time." Lupton was also the first to show this orchid produces seed in Ireland.
Orchids have suffered from overgrazing, yet many also require grazing. "Managed grazing and grazing at the right time of the year can benefit orchids. Grazing in late winter and into the spring can remove large invasive plants," says Lupton.
"The plants can be small with limited root systems; if areas aren't grazed or mown, common grasses and sedges take over," Duffy explains. Orchids tend to flower for two or three weeks over the summer, he adds, and excluding grazing during this time can be of great benefit.
Lupton is positive about the attitudes of Irish farmers towards orchids. "A lot of the farmers have been very supportive of my research," he says. "A number have been willing to take their cattle off during the flowering period. My experience has been that landowners are interested in these species."
Brendan Sayers, orchid expert at the National Botanic Gardens, describes the past and present distributions of orchids as yardsticks by which the health of the Irish flora can be measured.
He questions the wisdom of putting orchids under legal protection but not taking steps to allow them flower and set seed. Worryingly, even our more common orchids have declined, including the distinctive early purple orchid of the Burren, the delicate lesser butterfly orchid and the wonderfully variable early marsh orchid.
The National Botanic Gardens is currently developing native orchid beds and creating natural habitats where they can display Irish orchids.