- Resources K 2 Arboretum Historical development of the Arboretum The Arboretum in the Twentieth Century Kew's Arboretum holds a comprehensive collection of hardy trees; the majority are arranged by genera but those in the northern area form mixed decorative plantings. This division reflects the historical development of the Royal Botanic Gardens, Kew. For management purposes, the Arboretum is ...www.rbgkew.org.uk/ksheets/arboretum.html