Saga, which sponsored the recent Chelsea Flower Show, has doubled its cover for contents in the open to £2,000 offering total cover of £3,500.
Chief executive Andrew Goodsell said: "Gardens enhance the look of a house. Our recent research shows that 82% of people regard the garden as the most important feature when house-hunting.
"It makes sense to protect garden plants and equipment from theft or damage."
Meanwhile, More Th>n's head of home insurance, Craig Allen, said: "Unfortunately, expensive plants and landscaped gardens prove to be a prime target for thieves.
"As well as good insurance for plants and external contents, we would also recommend simple security measures such as security lighting, a wall or fence around the garden, and locking away all equipment."