Friends of the Arboretum, activities and events 2019–2021. Moe & Pirie report from the Arboretum: seasonal events and highlights from the collections from 2019 to 2021, including an account of the Arboretum’s 50th anniversary. They document challenges presented by invasive species, diseases, and damage caused both by a cold winter in 2020/2021 and by unexpectedly high salt content of water taken from Mørkevatnet after a dry June in 2020. Finally, they detail and illustrate contributions to the gardens by voluntary work and support from the friends association (Arboretets venner), with thanks.