The species list is one of several different measures of diversity:

Regarding species richness, the length of the species list for a site, is the simplest to understand, but the hardest to measure: no site in the world has a complete or constant species list. So lists for samples or selected taxa are chosen. In addition, we can use indicator groups, for which adequate taxonomic, distributional, and ecological data are available. The occurrence of such groups or species must be correlated with features of interest, such as specialists, ancient woodland, rarity - or richness of other groups which are harder to study.

A good botanical survey would aim to list all of the species, Subspecies, hybrids etc. (because many infraspecific taxa have conservation value) on the site, with detailed ecological information (including precise location) for the more interesting plants.