Over recent years, there has been a renewed interest in the care and value of historic botanical gardens – those with built heritage, historical collections or historical connections. Such gardens have made a major contribution to our understanding of the origin and development of botanical science, and to related disciplines such as herbal medicine, ethnobotany and ethnopharmacology. They have also influenced many of the crops we grow, the food we eat and the trees, shrubs and herbs that adorn our streets, parks and gardens (Heywood, 2018).

However, unless prompt action is taken, many of these unique resources risk falling into neglect, decay or in some cases total loss. This is already happening in many places and it is timely to celebrate and protect the treasures held in these historic botanic gardens. The 1st International Congress of Historic Botanical Gardens will be held in Lisbon, 12-13 October 2020, in the year this city becomes The European Green Capital.