The walnut genus (Juglans) plants belong to the angiosperm phylum Dicotyledonaceae (Juglandaceae). The book Chinese Walnuts (1992) describes that there are 8 species of walnut plants in 3 groups in China, namely

Walnut group: Walnut (J.regia L.)

Iron Walnut (J.sigillata Dode)

Walnut Rowan group: Walnut Rowan (J.mandshurica Max.)

Hebei Walnut (J.hoperiensis Hu)

Hebei Walnut (J.hoperiensis Hu)

Hebei Walnut ( J.hoperiensis Hu)

Wild walnut (J.cathayensis Dode)

Heart-shaped walnut (Ji walnut) (J.cordiformis Max.)

Jibbo walnut (Ghost walnut) (J.sieboldiana Max.)

Black walnut group: black walnut (J. nigra L.)