This dataset consists of plant species presence and abundance in different sizes and types of plots from 508 1km x 1km square sites surveyed across Great Britain in 1990. Many of the plots are repeated from surveys in 1978 and were surveyed again in 1998 and 2007. General information about the plot was recorded including plot number and type as well as species presence and (usually) cover. Data were collected under the Countryside Survey long term monitoring project managed by the Centre for Ecology & Hydrology.