With their delicate bobbing heads and pure white blooms, to most of us, they are merely a welcome sign that spring is around the corner.

But to galanthomaniacs – the name given to avid collectors - a carpet of pretty snowdrops are almost worth their weight in gold.

Now rare varieties of the humble snowdrop, along with its other common garden bloom, the crocus, have been included in a list that reveals some of the most expensive plants in the world.

They include a favourite wedding rose said to have cost more than £2million to develop, and a rare and endangered orchid which, if anyone can be bothered to scour Mt. Kinabalu in Malaysia to find it, comes with a price tag of £4,000 a stem.

The flowers are something of a step up from the kinds of blossoms typically found in a last-minute panic buy bouquet from the local garage.

But then it’s probably just as well – for the Kadapul flower, a species of cactus native to Southern Mexico and South America, only bothers to bloom for a couple of hours under cover of darkness. Worse, if anyone tries to touch it, the flower kills itself.

The eye-watering expensive £160,000 Shenzhen Nongke Orchid, an entirely man-made flower developed by Chinese agricultural scientists, meanwhile, takes up to five years to bloom.

The list of seven flowers has been compiled by experts from gardening website GardenBuildingsDirect, who say the blooms are among the world’s most expensive thanks to their rarity and their unique features.

Perhaps surprisingly, among the exotic flowers are a few with common-sounding names that will be familiar to even the most cack-handed gardener. Although, even if the saffron crocus – with its electric orange stamen and prized by chefs for its delicate flavour – was available at the local garden centre, it would set them back a cool £9,500.

Also making the list is the gardenia, a wedding flower favourite thanks to its floaty petals in soft, pastel colours. However because the blooms can’t be bought by the stem and have to be purchased as an entire plant, they can cost up to £45 each.

But it is the snowdrop, typically found growing wild on forest floors, which makes galanthomaniacs’ hearts beat faster.

“Snowdrops are really special,” says Brian Cunningham, head gardener at Scone Palace and a presenter on BBC’s Beechgrove Garden.

“Don’t tell my wife, but I once paid around £85 for a snowdrop bulb.

“Many people think snowdrops are just green and white flowers,” he adds, “but there are people who love them and will spend a lot of money on them.”

Thought to have been brought to Britain by the Romans, snowdrops became popular during the 18th century, when blankets of the pure white blooms began to cover meadows and woods across the country.

The Crimean War saw them boom in popularity, when the variety Galanthus plicatus was brought home by soldiers, some of them wrapped around their last mortal remains.

“They were planted in the grounds of Brechin Castle,” says Ian Christie, of Christie’s Alpines in Kirriemuir, who describes himself as “snowdrops mad” and who sells snowdrop bulbs which can cost over £700.

“Nature took its course, hybrids cropped up.

“There is now a bunch of very enthusiastic people who want to grow snowdrops and will a lot of money for a bulb that is unusual or rare.”

He has over 300 snowdrop varieties, among them a Galanthus Green Mile which sells for up to £200 for a single bulb. It’s overshadowed, however, by the ‘castle green dragon’, a delicate and almost entirely green snowdrop which costs around £400.

Even those can’t match the galanthus woronowii 'Elizabeth Harrison' – found in 2002 in the garden of a Perthshire woman, and which cost £725.10 for the bulb. Now cultivated, the bulbs sell for a less hefty £60.

The price tags, however, have also attracted dodgy snowdrop dealers who have been known to sell what are claimed to be rare and unusual snowdrop bulbs only for them to turn out to be common varieties.

“There are a lot of unscrupulous people out there,” says Mr Christie, who every year welcomes groups of snowdrop fanatics from Germany and the Netherlands to his Kirriemuir nursery. “It’s a very lucrative industry.”

According to Mr Cunningham, plant enthusiasts are attracted by the lure of having a rare bloom with a back story – such as the snowdrop – and are prepared to pay for the opportunity to grow them.

“People get a big buzz out of having a rare plant growing in their own garden,” he says. “You just have to look back to Victorian times when there was a huge rush among estates to have the latest conifers from America or to grow peaches and grapes in their gardens.”

A spokesman for GardenBuildingsDirect.co.uk said: “Many Brits have favourites at their local florist, love to grab a bargain supermarket plant, or will even pick up emergency flowers at the local petrol station.

“For the more well-off gardener or flower lover though, there are plenty of really rare species available from around the world, if you’re willing to pay the premium price tag that they command.”