Concrete? I'll have you know that reinforced concrete was invented by a gardener. The gardener in question was a Frenchman, Joseph Monier, who was trying to make the best-ever plant pot. (This isn't the kind of thing that gardeners just happen to know: I read it in a book about inventions I got at the Science Museum.) Gazing at Marseille's Unité, a block of apartments by Le Corbusier, it occurs to me that we have all been labouring under the misapprehension that gardening and concrete don't exactly go together. The truth is that the most brutal building always looks better with a lawn of verdant green. And some palm trees.
Even where a concrete building has no permanent garden, there is always the opportunity to make something more fleeting. This year, more temporary gardens than ever before have been created in London's concretiest districts, with a particularly good concentration around the South Bank. Celebrating 50 years since the 1951 Festival of Britain, the site has already been decked in bunting, beach huts and conceptual bandstands. Now just mix in some aeoniums and whoosh: you've got a garden party.
First, directly in front of the Royal Festival Hall, there is a tribute to Southend, Essex's legendary beach resort. Springing out of the paving next to the vintage ice-cream van selling exorbitantly priced Roskilly's, there is a proper seaside gardening border: wavy ribbon edges, palms, bottlebrush and a cockler's hut, all in boastful good health. It's true that the South Bank does like to get a bit beach holiday-ish even in a normal summer, but the Southend bed is a glorious celebration of the kind of municipal horticulture you usually get only by the seaside.
Next, climb the yellow staircase to the roof of the Queen Elizabeth Hall to find an entire vegetable garden ready to eat. This garden is the brainchild of designers at the Eden Project, in co-operation with a team from the housing charity Providence Row. Raised beds have been created, there's a greenhouse, but there's also a sort of little wild, wooded grassland area edged with logs on end, which is a delight. Add in a view over to the Savoy and Somerset House, and you've got almost the perfect English garden. (Also, there is a bar, which helps.)
Finally, if you have the energy, take a walk inland from the river to Union Street, not far from Tate Modern, and you'll find yourself in the Urban Physic Garden, constructed by the same team who last year created a blissful pop-up orchard on the same site. Showing off a huge range of medicinal plants and herbs, there are talks, workshops, film screenings and other events, in a surprisingly fragrant setting.
Gardens at the South Bank is open until 4 September. The Physic Garden is open until 15 August ( physicgarden.org.uk)
Get the look
1. Concrete planters
Kensuke's square concrete planter can be ordered in plain cool shades, or pigmented in colours from green to marigold. £50 untinted from thethirdnature.co.uk
2. Concrete herb wheel
Six sections to keep rampaging herbs in their place, in stylish grey. £70 from ingarden.co.uk
3. Concrete bench
Urbis makes a sleek "shell bench" with shades of Barbara Hepworth in concrete grey with ash legs (right). Very Cornwall, very 1950s, and very beautiful. For prices, contact urbisdesign.co.uk