Botanic gardens and arboreta around the world are repositories of diverse collections of useful plants in their gardens and seed banks. However, the crop and forestry communities often overlook these collections, and so they are an underutilised resource. For example, in analysis of the ex situ conservation status of 6,941 socio-economically important plant taxa using data from forestry and crop collections, but omitted collections in botanic gardens and arboreta. In this paper, we compared the socio-economically important taxa identified by Khoury et al. from GRIN-Global World Economic Plants (WEP) with data on living and seed collections held in botanic garden and arboreta, as recorded in BGCI’s global PlantSearch and ThreatSearch datasets. This analysis produced an assessment of the proportion of these taxa that are found in botanic gardens and arboreta, the number of gardens or arboreta they are found in and what potential they have to contribute to research, conservation and sustainable use. We also compared the species conservation comprehensiveness assessments carried out by Khoury et al. with the threatened status of those species, according to the IUCN Red List and other threat assessment methodologies in order to ascertain whether threatened, useful species are well-conserved in botanic gardens. At least 6017 of the 6941 socio-economically important WEP taxa (86.7%) were currently found in the living and seed collections of botanic gardens and arboreta with 1456 taxa (21%) held in >40 collections. Khoury et al. suggested that 6748 of the WEP taxa are of either medium or high conservation priority. However, our analysis suggested that just 1153 taxa have been assessed as threatened at a national or international level. We concluded that the botanic garden/arboretum community can contribute significantly to plant conservation and sustainable development, including data and material from many collections of socio-economically important taxa that are not present in the crop and forestry communities. We examined the reasons why botanic garden/arboreta collections are currently under-utilised and make recommendations for increasing their visibility and use.