USDA Hardiness Zone 5
RHS Hardiness Rating H6
A forsythia raised by Gerd Krüssmann at the Dortmund Botanic Garden in Germany from a plant grown as Forsythia × intermedia ‘Beatrix Farrand’; it was distributed by the Arnold Arboretum in the United States from 1969 (DeWolf & Hebb 1971). The pale yellow flowers are large and abundant, with broad corolla lobes serrated at their tips, but this plant is mainly remarkable for its leaves which are deeply toothed and almost lobed; it makes a compact shrub (Edwards & Marshall 2019). ‘Tremonia’ is represented in the UK National Collection of forsythia at Sculpture by the Lakes in Dorset by a plant received from MacPennys Nursery (M. Gudgeon pers. comm.). It is sometimes treated as a cultivar of F. × intermedia.