This important retrospective at Tate Modern contains some surprising disappointments such as her iconic but in reality rather flat New Mexico landscapes. It also contains any number of wonderful moments – the justly famous flowers and skulls and, best of all, her abstractions. I especially loved Blue And Green Music. The show includes a brilliant array of contemporary photographs of her including an Ansel Adams portrait of her and desert guide Orville Cox which is so fabulous it almost steals the show. Once you’ve seen all the pictures, walk across to the Switch House and take a look in the Louise Bourgeois room where a comparatively small version of Maman – truly iconic – and the extraordinary exploration of infinity titled Cell (Eyes And Mirrors) reveals that though a key modernist pioneer, O’Keeffe is a long way from being the 20th century’s greatest woman artist. Speaking of comparisons, the O’Keeffe exhibition includes four paintings of cottonwood trees from the decade after the Second World War. They are marvellous – but not as marvellous as a pen-and-ink drawing of a solitary tree in winter created nearly 500 years earlier by Fra Bartolommeo which is the highlight of a small but perfectly formed display of tree art at the Courtauld gallery.