First Poland sent us its plumbers and painters; now its garden plants are ousting our native species.

Britain’s traditional clematis varieties have been supplanted by Polish strains such as the General Sikorski, the Lech Walesa and the Jan Pawel II.

It has emerged that most of the trees sold in many British nurseries as native species also originated in eastern Europe. Most so-called English oaks, for example, are grown from acorns taken from Polish or other east European forests.

At stake is a share of a market whose total retail value is put at about £5 billion a year by the Garden Industry Monitor, a research publication.

Market experts estimate that about 90% of the plants on sale this Easter weekend, whether in DIY chains such as Homebase or in specialist nurseries, have come from overseas.

The scale of the shift is illustrated by sales of clematis. A series of strains developed in a Polish monastery now dominate the market. They were created by Brother Stefan Franczak, a Polish Jesuit monk, who started breeding clematis in the 1960s after finding seedlings in the garden of his monastery just outside Warsaw.

He created more than 60 new strains renowned for their bright colours, disease resistance and hardiness. Franczak refined these for up to 12 years before making them public, often with subtly subversive names chosen to defy Poland’s then communist regime.

Botanists liken Franczak’s work to that of Gregor Mendel, the Augustinian monk whose historic work on genetics in Brno (now in the Czech Republic) provided the first scientific explanation of how physical traits are passed from parents to offspring.

Franczak’s work was part of a much wider interest in plant breeding that helped create a network of renowned laboratories across eastern Europe.

By contrast in Britain, this coincided with Margaret Thatcher’s decision in the 1980s to slash Britain’s investment in such laboratories — which led to most of Britain’s plant-breeding centres being sold off or shut down.

Professor Stefan Buczacki, a former panellist on Radio 4’s Gardeners’ Question Time, was among the victims of that era. He left the National Vegetable Research Station in Warwickshire 20 years ago after being frustrated by funding cuts.

“Those cuts destroyed most of Britain’s investment in plant breeding and the sad reality is that most of Britain’s garden plants, trees and hedging are now imported,” he said.

“They mostly come through dealers in Holland but they originate in eastern Europe, Italy, Germany — all over the place. In fact, anywhere but Britain.”

Jon Rose, of Botanica, a Suffolk-based nursery specialising in native species, believes the collapse of the British nursery trade and its takeover by European dealers is having wider consequences on Britain’s wildlife.

He said: “Trees originating from countries with colder winters than ours are genetically different. They come into leaf and flower earlier than native ones.”

Some dealers believe gardeners have gained from the changes in the industry because they can now get a far wider variety of plants at lower prices.

Paul Ingrouille, general manager of the nursery at Raymond Evison Clematis Ltd in Guernsey, said the Polish invasion had given gardeners more choice.

He said: “Brother Stefan’s varieties are very good, strong plants and they tend to flower later in the season, which makes them popular.”

The Potted Garden Nursery near Maidstone in Kent and the Roseland House Nursery in Truro, Cornwall, are among those selling the General Sikorski variety of clematis, named after the Polish wartime leader who died in the 1940s.

Rachel de Thame, a writer in The Sunday Times’ Home section and presenter of Gardener’s World, said research in the Eastern bloc was proving increasingly important. “I think eastern European countries are the ones to watch now,” she said.

“It’s this idea that there are more hidden gems just waiting to be discovered by British gardeners which is so exciting.”

Roses are blue

Scientists have picked their first crops of blue roses, once thought an impossible horticultural phenomenon, after genetically modifying the species with genes from a pansy, writes Roger Waite.

Hundreds of rose bushes bearing the blue flowers have been planted in field trials in Colombia, America, Australia and Japan, and all have flowered successfully.

Now Florigene, the Australian company behind the creation, plans to scale up production by creating a commercial farm with more than 30,000 blue rose bushes somewhere in Japan.

“We are seeking permission to grow and sell the genetically modified blue roses in Japan and we plan to do the same in Europe,” said Steve Chandler, general manager of Florigene.

Roses do not have a gene that produces delphinidin, the pigment which makes flowers blue. However, the company’s scientists isolated such a gene in pansies and inserted it in a rose plant.

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