USDA Hardiness Zone 3
RHS Hardiness Rating H7
Felicitas Svedja experimented with forsythia breeding at the Central Experimental Farm, Ottawa, Canada, from 1960 (Cadic 1988); ‘Northern Gold’, a hybrid of F. europaea with F. ovata ‘Ottawa’, was selected by Dexter Sampson for its rich gold flowers (Dirr 2009), which are ‘pin-eyed’. The plant itself is hardy to USDA zone 3 (Stewart 2021). Though bred for use in very harsh climates (it is hardy to USDA zone 3 (Stewart 2021)) ‘Northern Sun’ flowers well as a young plant at Sculpture by the Lakes, Dorset, in conditions equivalent to zone 9 (M. Gudgeon pers. comm.) and is available in the UK from Bluebell Nursery (RHS 2020).