The botany or herbarium collection consists of more than 27,000 specimens, principally collected from across the historic county of Hampshire and further afield. The collection is fairly comprehensive with certain groups, namely mosses and flowering plants which are particularly well represented. Although most material was collected during the 20th century, there is a significant number of 19th century specimens and, remarkably, a preserved herbarium specimen of Ling (Calluna vulgaris) has survived since 1737.

The collection includes the herbaria collected by W A Bromfield, A W Westrup, N E G Cruttwell, F Rose, D E Allen, E Rothwell and R P Bowman; the Hart, Malmsbury and Crowley, which are of more than local significance.

The fungi collection consists of over 2,100 freeze-dried specimens. The overwhelming majority of these specimens were collected from across Hampshire, with some collected from national and international sources.