Beverly Allen, Yellow Lotus (Nelumbo lutea). Shirley Sherwood Collection. © the artist

Botanical artworks from two world-class collections that have been kept behind the scenes for study purposes have now taken their place on public display in a new gallery at Kew Gardens.

From dainty violas to mighty palms, extinct species and rare fungi to carefully bred strains of decorative tulip, treasures will be on display from April 19 2008 in the newly-built Shirley Sherwood Gallery, all year round.

This is the first time public access has been made possible for many of the works which need a climate-controlled environment, such as pieces dating back to the 18th century by masters like GD Ehret and the Bauer brothers, and vintage copies of Curtis's Botanical Magazine.

Unknown artist, Anemones, 17th century. © RBG Kew

Kew holds one of the world's greatest collections of botanical art, totalling more than 200,000 items. They include illustrations by prolific 19th century artist Walter Hood Fitch, as well as contemporary works by artists such as Christabel King and Stella Ross-Craig.

The gallery, which will run a rolling programme of exhibitions, will also display works from the collection of Dr Shirley Sherwood – after whom the gallery is named. Dr Sherwood, Vice Chair of the Picture Committee of the RHS and former Kew trustee, has written several books of botanical art and has collected works from 30 different countries by more than 200 contemporary artists.

Interior of the new gallery. © RBG Kew

Dr Sherwood's works complement the wealth of images from the 18th and 19th centuries in Kew's collection, which includes illustrations of extinct species for which the artwork may be the only surviving record. For this reason, the historic illustrations are not only great works of art but also rich scientific tools for taxonomists, horticulturalists and researchers.

With a quarter of the world's species of flowering plants threatened by extinction in the next 50 years, Kew has a vital role to play in the science and communication of plant conservation. Arranged systematically by plant families, its collection of botanical art forms part of the National Reference Collection.

Unknown artist, Livistona mauritina, 19th century. © RBG Kew

The new building, designed by architects Walters and Cohen, provides the right environment for the works to go on display for the first time. It is attached to the Marianne North Gallery, named after the Victorian amateur artist, where 832 of her lavish paintings created around the world adorn the walls.

Restoration of this gallery is in planning, and an extension to the Herbarium, Library and Archives behind it will open in 2009.

Alexander Viazmensky, Fly Agaric ( Amanita muscaria), 1990. Shirley Sherwood Collection. © the artist

The first exhibition in the Shirley Sherwood Gallery features highlights from the two collections, indicating their scope and richness. It gives an overview of the most significant artist from c1700 through to the present. The delicious names of works and artists on show include Maria Sibylla Merian's (b.1647) 'Polyanthus and primroses', PJ Stroobant's 'Bromelia agavoides' and 'Cleistocactus fieldanus' by Christabel King.

The next exhibition, opening in autumn 20008, will focus on trees with detailed illustrations of various specimens.