London house prices: how much does a garden add to the value of your home?

London is turning into a city of urban farmers. Almost one in four people with a garden devotes some outside space to growing their own food, according to a new study.

These numbers do not include the countless other growers in the capital who are turning their balconies and windowsills into vegetable gardens — and as estate agents know, gardens are not just good for produce, but also for adding value.

TV chefs, the warmer London climate, the growing popularity of organic food and the trend to relax and enjoy the de-stressing satisfaction of producing your own veg are encouraging this growing spree.

Last winter’s torrential rain in Spain and consequent shortage of lettuce, courgettes and other vegetables in British supermarkets earlier this year led to a run on seed buying. Crocus, a leading gardening website, reported sales of lettuce seeds increased 270 per cent year on year.

Celebrities from Jamie Oliver to David Cameron to Gwyneth Paltrow and Kate Moss have their own vegetable plots, while new developments from Battersea Power Station in the south to new-homes estates in the East End feature residents’ rooftop plots and allotments.

“It is becoming ever more popular,” says Chris Manderson, sales manager of Foxtons in Hackney. “I think a lot of people who have moved to Hackney are eco-conscious and care about where their food comes from.”

When it comes to buying property, 72 per cent of clients surveyed by Foxtons say they would pay more for a home with a garden, and demand is inevitably highest in summer. The size of the “garden premium” varies wildly across the capital, but a straw poll of agents suggests outdoor space could add up £90,000 to your home’s value in London.

“With flats the premium is around £30,000 to £50,000 for a one- or two-bedroom garden flat,” says Manderson. “With houses the market is considerably different. A garden is the be-all and end-all of buying a house.

“We recently marketed a two-bedroom house on Sylvester Road, Hackney Central, for £895,000. If it’d had a garden it would have been more like £1.1 million. It is best to wait and put flats and houses without gardens on the market in the winter.”

The research also found that the average London garden measures 52ft by 36ft, while the flowers most commonly grown in them are, in order of popularity, roses, lavender, bluebells, tulips and hydrangeas. Some 80 per cent of gardens include a lawn, and more than half have a deck or paving.