• London Open Garden Squares Weekend will see more than 200 “hidden and little known” gardens swing their gates open to the public this Saturday and Sunday. Featuring 20 more gardens than last year’s event, the gardens range from classic London square parks to rooftop gardens, community allotments and ecology centres as well as gardens attached to restaurants and historic properties. They include Highbury Square – former home of the Arsenal Football Club, Barnsbury Wood – London’s smallest nature reserve, the Cordwainers community garden in Hackney, Garden Barge Square which will see a floating garden created on the decks of barges, the garden at the PM’s home of number 10 Downing Street, and The Roof Gardens, located above the former Derry & Toms department store in Kensington. One £12 ticket gains access to all gardens (excepting those with special conditions) while National Trust members are half-price and children under 12 go free. For more and a full programme of open gardens, head to www.opensquares.org.

• Comics created during World War I are the focus of a new exhibition which opened at the Cartoon Museum in Bloomsbury this week. Never Again! World War I in Cartoon and Comic Art features works by British cartoonists Alfred Leete, Bruce Bairnsfather, William Heath Robinson and Donald McGill and includes more than 300 images ranging from political and joke cartoons taken from newspapers and periodicals and children’s comics to comic cigarette cards and publications produced in the trenches by serving soldiers. There are also some more recent works such as the 1980s comic strip Charley’s War and drawings from the Horrible Histories series. The exhibition runs until 19th October. Admission charge applies. For more, see www.cartoonmuseum.org.

• Explore the world of garbage in this new exhibition opening at the Science Museum in South Kensington on Monday. The Rubbish Collection aims to use 30 days worth of the Science Museum’s waste to “expose the beauty, value and volume of what we call ‘rubbish'”. Visitors are able to take part by collecting, sorting and documenting the rubbish generated by the museum which will then be photographed by artist Joshua Sofaer before going on to be processed for recycling or to generate electricity. During a second phase of the exhibition, Sofaer will bring the rubbish back into the museum at different stages of processing. The exhibition is part of the museum’s Climate Changing programme. Runs until 14th September. For more, see www.sciencemuseum.org.uk.