Several additional of Forsythia are grown and may escape, including F. viridissima, the green-stemmed Forsythia, with pith chambered throughout and simple leaves, and F. ovata, the early or Korean Forsythia, with stiffly upright twigs and ovate leaves. Many cultivars are also grown.
1. Pith chambered between nodes and solid at the nodes; leaves all simple.
1. Pith hollow throughout; leaves of vigorous shoots three lobed or trifoliate.
All species found in Forsythia
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. July 14, 2020. https://michiganflora.net/genus.aspx?id=Forsythia.