What is an herbarium voucher?

An herbarium voucher is a pressed, dried specimen of a plant that is attached to a sheet of paper. A label is also attached to the paper to identify the plant and to explain where, when and by whom the specimen was collected. The sheet is commonly 11.5 inches wide and 16.5 inches long. Plants larger than this size must be folded to fit, or if the are very large, only the portions essential to identify the plant are mounted. Vouchers of trees, for example, typically include a twig with leaves and buds, or the flowers and fruits.