Collectors with a fascination for gardening are expected to bid up to £1,200 for a single watering can.

The 18th Century Dutch can, decorated with images of female heads, is among a collection of 18 vintage water vessels up for auction at Sotheby's near Billingshurst.

A French copper can dating from about 1820 is also expected to whet the interest of enthusiasts who are willing to pay hundreds of pounds for the objects of their desire.

The lots could together fetch up to £5,000.

In addition, there will be dozens of garden seats, statues and fountains up for auction.

Bidders can also buy an early 20th Century bronze mermaid, which is expected to sell for between £15,000 and £20,000.

A rare 1.5m-high, cast-iron urn, made in 1860, should fetch up to £12,000.

According to Sotheby's, interest in garden collectables is growing rapidly and has spawned a core of enthusiasts with a particular interest in watering cans.

Among them is Sotheby's own director Alistair Morris.

Mr Morris said people were willing to pay large sums of money largely due to TV garden makeover shows, which had made the hobby fashionable.

He said: "The gardening fashion is very well established. Programmes such as Gardener's World and Ground Force have made it very popular.

"Gardening has always been popular but I think it's more so now than it has been for some considerable time.

"This has a knock-on effect with collectors."

The collection has come to Sussex from the West Midlands, where a green-fingered expert spent more than 25 years trawling sales and auctions.

Mr Morris said: "There is nothing more emblematic of gardening than the watering can. While we sell a lot of garden statues, we find people also want decorative items."

He expected interest from collectors in North America and from across Britain.

Rupert van der Werff, head of garden statuary and architectural items at Sotheby's, said: "To have this many antique watering cans in one place is quite exceptional. There aren't that many around of such good quality.

"They are functional objects used in the garden, which often have a hard life.

"In the past they were mostly thrown away or sold for their metal content."

The collection has been kept in the attic of John Massey, a director of the 120-year-old Haws company, which makes watering cans.

Mr Massey started collecting the items to study how designs had changed and to get fresh ideas from the old cans.

With retirement approaching, he decided to sell the collection, including several copper cans, which are the most sought after by buyers.

The cans will be auctioned among a selection of banal and bizarre garden and architectural items at Sotheby's on May 20 and 21.

A collection of decorative fossils is also expected to create interest, including a fossilized mammoth tooth, dinosaur eggs and Chinese stalactites dating back 180 million years.

For more information about the auction, call Sotheby's on 01403 833561.