The Herbarium is internationally important and worldwide in scope. It has approximately 120,000 herbarium specimens, with a special emphasis on South-East Asia, notably Thailand numbering approximately 22,000 sheets, including over 400 type specimens. It is regarded as the second most important collection of such material in the world.
The British collection numbers 55,000 specimens and is particularly representative of Scottish material. Specimen information is good relating to identification of species, collector, collection dates and location while many of the specimens have additional data stored with them, including notes made by researchers relating to individual specimens.