These unused and undated postcards of the Botanical Gardens, Grange Road, landed on my desk from differing directions during the Christmas & New Year break. They seem to be in real colour, therefore I would guess that the Rose Gardens card is from 1950s and the archway from '60s.
The archway picture is labelled ‘pergolas’. My dictionaries list no plural form but define a pergola as: a passageway of columns supporting a roof of trelliswork on which climbing plants are trained to grow.
So there we are. Jolly nice too. Romantic, even!