Mary Grierson - Telegraph On the outbreak of war Mary Grierson joined the WAAF, serving with the Photographic Reconnaissance Unit at Medmenham in Buckinghamshire, analysing and interpreting aerial photographs - work which no doubt enhanced her powers of observation. After demobilisation she joined Hunting Aerosurveys, a company making maps from aerial photographs. "If you drew a contour, it had to join up," she later told the writer Ursula Buchan. You couldn't leave anything to guesswork. No more than you can if you are doing a botanical illustration. Mary Grierson was living in Hertfordshire, and in her spare time she roamed the countryside indulging her love of wild flowers. One spring day she came across a large colony of Pasque Flowers, inspiring her to take up flower painting. "It was in the evening and the sun was shining, and all the hairs were glittering," she recalled. She picked a single flower, took it home and painted it. At about this time Hunting Aerosurveys sent her on a pen-and-ink drawing course at the Field Studies Centre at Flatford Mill, on the Essex-Suffolk border, a location celebrated in the work of John Constable. She found the experience so fulfilling that she returned there to study under the painter and botanical illustrator John Nash, younger brother of the great war artist Paul Nash. Once established at Kew, Mary Grierson found herself offered many outside commissions. Her first big project was from the publisher Paul Hamlyn, who invited her to illustrate a series of volumes on Orchidaceae, with P Francis Hunt (head of the Orchid Herbarium) writing the text. In the event, only one volume - which took 10 years to produce - was published, in 1973, but she regarded her illustrations as "the most spectacular of my work." After her retirement in 1972, Mary Grierson was constantly in demand. Among many projects, she continued to work for Curtis's Botanical Magazine; undertook a series of paintings of tulip species which was bought by the Library at Kew in 1992; and provided illustrations for the catalogues of the Dutch bulb company van Tubergen. In 1973 she was invited to go to Hawaii and paint some of the islands" rarer species, and for several years she visited the islands annually; in 1996 the fruits of this work appeared in A Hawaiian florilegium: botanical portraits from paradise, with text by Peter Shaw Green. She illustrated many other books, among them The Country Life Book of Orchids and An English Florilegium (also with Peter Shaw Green), which featured 150 of her paintings. She designed stamps for the Post Office, and painted the flora of the Negev and Sinai deserts for the Israeli Nature Authority. Mary Grierson received the Royal Horticultural Society's Gold Veitch Memorial Medal in 1984, and its Victoria Medal of Honour in 1997. Her work is held at museums around the world, but the finest collection resides at Kew, which has more than 1,000 of her watercolours and pen and ink drawings . She was unmarried. Mary Grierson, born September 27 1912, died January 30 2012