Bokrijk houses one of the largest plant collections in Belgium. The park started in 1965 with the construction of the arboretum on an area of 18 hectares. Part of the collection was developed within thematic ornamental gardens: a Mediterranean garden, a fern garden, a woodland garden and a marsh garden. In Bokrijk you can visit the national bamboo collection. The arboretum also has the largest reference collection for holly (Ilex) in Europe. The arboretum is an official testing ground for holly associated with the American Holly Society. Bokrijk is also known for rhododendron and azaleas.
Parts of the plant collection are also outside the arboretum. For example, the herb garden, the vegetable garden (old varieties) and the historic standard orchard are part of the open-air museum. The scent and color garden is located near the castle and the playground of Bokrijk. The Bokrijk Arboretum collection can be consulted via PLANTCOL. The arboretum is open all year round.