Threatened species of conifer from around the world are being preserved in a ground-breaking Scottish project

They can be the source of awe, delight or scorn, but however you feel about conifers, they have a habit of grabbing our attention. This group of plants has had its share of negative press -

towering hedges of Leylandii causing neighbour disputes and swathes of sitka forestry standing accused of spoiling the countryside. But conifers are also among the most fascinating trees on the planet, from the 100-metre plus redwoods of California to the foot-high Juniperus communis 'Compacta'. Exotic species of conifer discovered back in the 1850s by plant hunters grow as happily in Scotland as the native yew, juniper and Scots pine, but this group of plants faces a real threat to its survival in the wild.

Some 348 of the world's 722 conifer types are of "concern" status says the International Union for Conservation of Nature. Threats include logging, uncontrolled forest fires, open-cast mining and conversion of forests to pasture and arable land. The scale of the problem is vast, but a Scotland-based initiative is working to combat it. Martin Gardner is project manager of the International Conifer Conservation Programme, at the Royal Botanic Garden Edinburgh (RBGE). He says that a simple shortage of space sparked the programme to life.

"They're large trees, so even in terms of RBGE with its four sites - Logan, Dawick, Benmore and Edinburgh - we were finding we just didn't have enough space to have conservation collections," he says. "Particularly as you need to grow more than one individual to have a good representation of the genetic material from the wild. The conifer programme started with a suggestion from the Marquis of Bute, who at the time was chairman of the trustees at Benmore. He said 'you're obviously running out of space, I can hand over 100 acres of land on my estate and you can expand there'." This led to the creation of a network of sites which would take conifer conservation into privately owned land and gardens. In 1991 the project formally began, and today there are 135 sites throughout Britain and Ireland growing 13,000 conifers which originate from the RBGE's own overseas seed-collection visits.

"We've broadened the genetic base of the plants in cultivation," says Gardner. "We know where each plant comes from and that's very important. The end product is to have material ready if it is needed to try to restore the populations in the wild - exactly as zoos do." This "ex-situ conservation" is one strand of the project, which also includes field survey work in Chile, the Caribbean, New Caledonia, SE Asia and China. Training programmes allow students from partner countries such as Chile to access the expertise at RBGE, to develop skills and knowledge which they can then put into practice. "Horticulture plays a vital role in the conservation of the diversity on this planet for the simple reason that horticulturalists develop the skills of propagating and growing plants," says Gardner. "Without the knowledge of how to propagate plants and how to grow them in different regimes, we would have no hope of restoring habitats."

Plant hunters such as David Douglas, Archibald Menzies and George Forrest played a key role in originally bringing conifers to Scotland. The plants were intended to be grown as ornamentals, while some were adopted for forestry. "There was a lot of one-upmanship at that time," says Gardner. "We have this wonderful history in Scotland of these big estates who'd aspire to have the tallest trees - people used to cheat by planting trees on mounds. What was extraordinary then was that nobody knew whether they were going to grow or not. Today with the conifer programme it's made so much easier because the benchmark is there - we look around and we see the indicator species and it gives us an idea of what we can grow."

Perthshire is home to some of the country's most impressive conifers and it's here that a collaboration between RBGE, Forestry Commission Scotland and the Perth & Kinross Countryside Trust is under way. The iCONic project involves collections of different conifer species from across the temperate world being established in Perthshire forests, estates and gardens. About a dozen landowners are taking part, and between 5000 and 7000 trees will be grown. These are all trees which are threatened in their native habitat, including Australia's Tasmanian cedar, the Japanese umbrella pine and the Chilean pine, or monkey puzzle tree. The aim is to aid the conservation effort, raise awareness of the problem and to introduce people to new trees, maintaining the tradition of Scottish plant hunters.

Back at the RBGE, a project is under way to replace the holly hedge that surrounds the gardens with a hedge of Taxus baccata, the common yew. "Yew has a big distribution throughout Europe and North Africa, but go to any native yew forest and you will find that most of them have been mutilated," says Gardner. "We are going to wrap ourselves in our conservation message. Thirty per cent of the hedge will be from famous heritage trees in Great Britain and Ireland; the other two thirds are going to be from threatened forests throughout its range in the wild." The result will be 2200 plants, all traceable. Interpretation boards positioned on Arboretum Road will mean that even people not going into the garden will be able to read about the conservation message.

"Plant groups have periods of time when they're in vogue, they go out and come back again. There's still a big interest in growing conifers," says Gardner. The number of species on the threatened list continues to rise, but the work of the ICCP means that Scotland is playing a key role in ensuring the survival of conifers in the wild, as well as at home.

A show and tell: conifer conservation event with Martin Gardner is at the RBGE on Wednesday and a conifer identification event will be held on 28 November. For details tel: [phone] or go to www.rbge.org.uk

• This article was first published in The Scotsman on November 6, 2010