Botanical art has a history spanning thousands of years, yet, amazingly, there’s no gallery anywhere in the world dedicated to the subject. This is about to change. Directly opposite Decimus Burton’s Temperate House in Kew Gardens, a new modern glass structure will give visitors access to the finest examples of botanical art all year round. Opening to the public on April 19, the Shirley Sherwood Gallery will show examples from the Kew collections which hold more than 200,000 pieces dating from 1370 onwards beside works owned by the leading collector of contemporary botanical art, Shirley Sherwood, who has been instrumental in financing the project in conjunction with Kew. This juxtaposition of one of the finest botanical art archives with some of the fore-most modern botanical pictures will show the strong heritage of this field and the renaissance that it’s experiencing.

With only a few weeks to go, the exhibitions team at Kew, led by Laura Giuffrida and collaborating closely with Dr Sherwood, is putting the final touches to the inaugural exhibition, ‘Treasures of Botanical Art’, which runs until October. The process has been, at times, revelatory. Members of the Kew Library, such as Marilyn Ward, the curator of illustrations, have an intimate knowledge of the collections, but no one can hold nearly a quarter of a million images in their memory. The collection at Kew is renowned for encompassing the great names of botanical art Georg Ehret, Pierre-Joesph Redouté, Franz and Ferdinand Bauer, Walter Hood Fitch but the research has thrown up things that are also unexpected. For instance, there’s a fascinating painting of a sunflower by an anonymous artist in India in the 18th century. Although it displays touches of the Euro-pean style expected by the Briton who commissioned it, it’s redolent of the technique and aesthetic of Mughal art.

The mixture of modern and historic pieces selected for the exhibition has produced some thought-provoking pairings. A primula by the 17th-century painter Maria Merian, one of the finest female botanical artists, is to be married with a modern watercolour of the same subject by Bridget Edwards; an homage to the Dutch Old Master Simon Verelst by modern artist Alvaro Núñez will finally hang next to its inspiration; and Fitch’s 19th-century study of lilies will be joined by a large-format version by the RHS Gold Medal-winner Pandora Sellars.

The new building continues this union of old and new. Designed by architects Walters and Cohen, the £3 million structure consists of a box within a box, separated by an ambulatory space used for displays and visitor amenities. The main gallery is situated within the inner cube, where climatic conditions can be carefully controlled. This largest area, with the gallery’s smaller spaces, gives a total exhibition capacity of more than 3,000 sq ft. The glass façade offers unencumbered views, not only of the Kew landscape, with its seasonal changes, but also of the nearby Victorian building dedicated to the paintings of 19th-century botanical artist Marianne North. The two galleries are linked by a connecting gallery, in which changing selections from the Sherwood Collection will be displayed.

This new endeavour is part of a wider range of building currently in pro-gress at a Kew. A walkway at canopy height dedicated to the life of trees (the subject of the Sherwood Gallery’s second exhibition) will open later this year, and Kew’s Herbarium and Library will soon move to a new state-of-the-art facility. In addition, it’s planning to close the Marianne North Gallery this summer for extensive and long-overdue restoration. These projects will all be completed by 2009 to coincide with the 250th anniversary of Kew Gardens.

In creating the new gallery, Kew and Shirley Sherwood have ensured that the widest possible audience will be able to explore and appreciate fully the fascinating diversity within the field of botanical art. What promises to make the experience more enthralling is the setting, which is confident and cutting-edge and certainly contains no wallflowers. The Shirley Sherwood Gallery opens on April 19. The opening exhibition, ‘Treasures of Botanical Art’, runs until October 19 (020–8332 5655; www.kew.org)