The site of Botanic Garden Meise is a 92 ha domain near Brussels. It has been assembled from parts of two historic castle parks. For more than 75 years it has been home to a collection of plants, as well as a research institute dedicated to botany, forming one of the largest botanic gardens in Europe but also an important tourist attraction close to Brussels. Some habitats get a high degree of disturbance, either due to garden maintenance, or from the large number of visitors. There are also managed and more natural areas. A variety of terrestrial and aquatic habitats occur, among which valuable woody (semi-)natural areas, and also managed meadows.

The study of biodiversity in the park has relealed an exceptional species richness in many taxonomic groups. More than 600 wild vascular plant species have been found since 2002, including rare species that were inadvertently introduced during the 19th century, so called wood lawn neophytes . Since 1993 the ectomycorrhizal fungi have been monitored, and there are observations of 52 Red List species in the domain. The park is also the richest Belgian site for Laboulbeniales (Ascomycetes), obligate ectoparasites of Arthropoda. Especially the wet ash-alder forests hold a number of rare and unique taxa and host-parasite combinations, some of them with only a few localities known worldwide. Moreover, the domain is a biodiversity hotspot for lichens and lichenicolous fungi, among other factors as a result of management, such as the regular maintenance of the undergrowth which has a positive effect on light-loving epiphytic lichens, and also due to the diversity of habitats and the large range of different substrates of varying age and of ecological conditions. Another well represented group are diatoms (Bacillariophyta), of which a mere survey in a small pond already yielded two species which have been described as new to science. The site is also rich in fauna, for example rare bat species that overwinter in our historical underground ice cellars. The diverse range of cultivated species also attracts an enormous range of arthropods and plant pathogens, which we know exceeds what we know of it.