Marianne North defied convention to travel alone to countries including Jamaica, Borneo and Tasmania, where she painted botanical landscapes, documenting more than 900 species.
The gallery is the only permanent solo exhibition by a female artist in Britain. North's paintings have been hung frame to frame, from floor to ceiling, since the gallery first opened its doors in 1882, so the collection has been deteriorating.
The Heritage Lottery Fund awarded the gallery £1.87m towards the project in July, to renovate the building and collection. But Kew needs to raised £2m to complete the project, and has asked the public to "Adopt a Painting" to raise funds.
The gallery aims to be reopened in September 2009 as part of Kew's 250th anniversary celebrations. It will be part of the "arc route", designed to draw visitors to less-visited areas of the gardens.