USDA Hardiness Zone 5
RHS Hardiness Rating H6
A hybrid raised by Dr Karl Sax at the Arnold Arboretum in 1941; Sax crossed an unrecorded clone of Forsythia × intermedia with the recently introduced low-growing Korean F. saxatilis (or with F. japonica in Donald Wyman’s account (Wyman 1961), which is less reliable).
‘Arnold Dwarf’ makes a plant less than 1 m tall whose branches layer easily at their tips, making it of some use for ground-cover. Its strongly-toothed leaves are only 3–5 cm long, and bright green. Its soft yellow ‘pin-eyed’ flowers are unreliable (Bean 1981; Edwards & Marshall 2019).