The Greenwich-based Meantime Brewery is behind the initiative, for which it has created a Boris Johnson scarecrow to protect the fledgling hops.
Pubs in the capital are also being encouraged to take part, with the brewer offering hop shoots to licensees who get in touch, which will be used to make the Meantime True Brew of London once they are harvested in the autumn.
The brewer then plans to make a keg beer which has been matured for eight weeks and released before the end of this year.
“London is an exciting place to be a brewer right now,” said CEO Nick Miller.
“The variety of ingredients at our disposal is huge and it allows us to pack flavour into our beer. I hope that our urban hop farm will make more of the public aware of that fact and help to get them to switch to beer that is locally made.
“While brewing was an industry that declined to an almost terminal point in London during the 1990s, a new generation of modern craft businesses has got it back on its feet and there are some fantastic beers that are bold, full of flavour and character – just like the city itself. The True Brew of London is about championing our Capital’s rich brewing heritage. “
The move comes as London is experiencing a dramatic revival of interest in brewing – with around 40 breweries of varying scales now making beer in the capital.