The British are now embracing al fresco living with a vengeance. These days no garden is complete without its collection of tables, chairs, barbecue and trampoline. Throw in a state-of-the-art rotary mower, some attractive plants and a couple of bicycles and you have quite an expensive hoard.

A study by Confused.com, the price comparison website, shows that gardens are a goldmine for criminals, with many now containing items with a combined value of more than £1,000. A gas barbecue can cost as much as £400, a petrol-driven rotary mower could set you back more than £450 and you might have to fork out £470-plus for a garden table and four chairs.

Little wonder that thieves are now actively targeting gardens. Research by Gocompare.com, another price comparison website, shows that almost a quarter (24 per cent) of UK households have fallen victim to garden crime. The most commonly stolen items were bicycles, which made up more than half of all thefts. Other items that proved popular with thieves were garden furniture, expensive plants and garden tools. Plants and furniture were the most frequent targets for vandalism.

The bill for replacing stolen and damaged items often runs into hundreds of pounds, so it is vital to check whether you are covered for such losses on your home and contents insurance. Fixed items, such as garden sheds, gates, fences and conservatories, would normally be covered under buildings insurance, while moveable objects, such as play equipment, tools and garden furniture, would come into the contents category.

Steve Sweeney, of Moneysupermarket.com, another comparison website, says: “All insurers differ on what is and is not included in your cover for gardens, so it is important to check the small print.”

Even if your insurer does cover garden items, you need to check whether there are exclusions for things that are not packed away after use. Hayley Parsons, chief executive of Gocompare.com, says: “As a general rule, you are on firmer territory if items are kept in a garage or shed that is bolted and locked. Anything lying around in the garden, such as a lawn mower or expensive toys, could be hard to claim for because the insurer will be able to say that it wasn’t locked away.”

Another grey area relates to what are known as “contents in the open”, such as garden furniture, barbecues and ornaments, which would usually be outside but could be locked away in winter. Insurers tend to deal with things in this category by offering much lower levels of cover, with a claims ceiling of as little as £250.

As any parent of young children will know, bicycles are frequently left lying around in the garden, though they are not normally considered as garden items. This means that insurers may refuse a claim for theft unless the bike was in a locked shed or garage.

On the other hand, it is becoming more common for plants and shrubs to be covered against theft or damage. But not all policies do this, so you need to be prepared, if necessary, to pay separately for extended garden cover. Saga is one insurer that offers this as an add-on for about £30 a year.

Mr Sweeney says: “Garden lovers need to be aware that damage to plants, shrubs and trees through extreme weather is not normally included in a standard policy.”

Gocompare.com and Moneysupermarket.com have each produced research showing the different levels of garden cover offered by the leading insurers.

Marks & Spencer home insurance offers unlimited cover for contents stolen from a shed, plus unlimited cover for theft and damage to plants in the garden. Ornaments, garden furniture and barbecues are also covered, provided that they are within the boundaries of your home.

Esure provides up to £2,000 of cover for garden contents and £2,000 for items in outbuildings. Sheila’s Wheels offers the same £2,500 protection for garden contents but raises the outbuildings figure to £5,000. More Than splits its cover into £2,000 for plants, garden and trees, with a further £2,000 for garden furniture, barbecues and ornaments. Outbuildings cover comes within the overall home contents limit of £75,000.

Halifax and HSBC both offer £500 of outdoor cover and £2,000 for outbuildings, while Barclays and Aviva both allow you to boost the outdoor contents limit from £500 to £1,500 by buying extra garden cover. Tesco’s Standard and Finest home policies both offer £1,000 of cover for garden contents, but its Value policy does not.

Anita Horton, of Walsall, is very glad that her family’s home insurance covered garden items. Thieves got into her back garden and made off with an ornamental swing, two benches, two chairs and a table.

Mrs Horton, a 42-year-old teaching assistant, says: “Thieves climbed over a 6ft fence at the bottom of our garden and took all the garden furniture, worth about £500. They appear to have lifted the heavy wooden items over the fence. We were horrified to lose our garden furniture and didn’t know whether we could make a claim on our policy.

“Fortunately, we were covered for the loss of all the items on our esure policy. We were able to replace them with exactly the same items.”

Below is a list of tips on how to make your garden more secure, but membership of Neighbourhood Watch is the only one likely to bring a reduction in your insurance premium.

Crime prevention checklist

• Keep all items of value out of sight and locked away, especially bicycles and lawnmowers.

• Install security lighting.

• Keep hedges and fences in good repair. Plant prickly shrubs or hedges to deter intruders.

• Secure expensive plants with wire pegs dug into the ground.

• Use an ultraviolet security pen to mark items with your postcode.

• Join your local Neighbourhood Watch scheme.

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