The habitat of the species is poorly known. The available data indicate that the species developed on the sheltered slopes of Serra da Tronqueira, São Miguel Island, Azores, but the population was subsequently destroyed in a landslide.[8][9]
A cultivated population was maintained in the Thames Ditton garden of Hewett Cottrell Watson, the author who described the species.[5] Several seeds were germinated and produced annually flowering and fruiting plants. In the winter, the plants were sheltered in a greenhouse to protect them from frost, and in the summer they were planted in the garden. However, at the end of May 1867, almost all of Watson's plants had died due to a late frost. One of the three surviving plants bloomed again in the summer of the next year, which made it possible to continue to cultivate the species.[2] After Watson's death a specimen was transferred to the Royal Botanical Gardens of Kew.[5] Due to unsuccessful propagation, today only herbarium specimens remain.[9]
^"The Australasian Virtual Herbarium". The Australasian Virtual Herbarium. Council of Heads of Australasian Herbaria (CHAH). 2020. Retrieved 12 April 2021.
^GBIF. "Vicia dennesiana". Global Biodiversity Information Facility. Retrieved 26 April 2021.