Organised crime is threatening to make dozens of Scotland's native wild flowers extinct, conservationists and landowners warned yesterday.

Every county in Britain is feared to lose on average seven species a decade because of theft. And gangs are now stepping up their activities north of the border, exploiting the more relaxed laws governing wildlife and natural flora.

Such is the concern among estate owners that the Scottish Landowners Federation has issued a warning to its members to increase security.

Gangs stealing to order are concentrating on rare bulbs such as varieties of snowdrops that can fetch up to £45 each from unscrupulous garden centres, mainly in England. Other specialist bulbs sell for up to £25.

Alistair McNeill, of the Scottish Landowners Federation, said: "We have warned our members to be vigilant at all time ... Snowdrops are grown semi-wild and they best regenerated when they are harvested when the blooms fade. Quite a lot of land managers have contracts with seed merchants and garden centres to sell these at the end of the season but this doesn't stop cowboys from moving in and removing them under the cover of darkness."

Bluebells and mosses, which are popular in hanging baskets, are also being harvested illegally. Another casualty is the miniature white water lily, not commercially viable, but which grows in the north-west Highlands and is highly prized as a plant for small garden ponds.

With other wildlife crimes such as the trade in rare eggs or endangered species, the illegal industry is worth an estimated £2bn a year.

Niall Bennet, of the wild flower charity Plant Life, is calling for a change in the law, to allow Scottish courts to impose the same kind of penalties as in England and Wales, where criminals risk heavy fines or sentences under the Countryside Rights of Way Act 2000.

"Wild plants and flowers aren't just beautiful to look at, they are a barometer of our land's health. What happens to them affects insects, birds, bees and large numbers of animals," he said.