The stand of Caucasian Wingnut that straddles the stream feeding the Lake is one of the most outstanding features of the Garden. Originally it consisted of two trees, but it is now an immense thicket of suckers. Pendant, plaited green catkins elongate in July before developing into winged fruits. A Black Walnut (Juglans nigra) formerly stood by the Magnolia trees on the other side of the path, but it was removed in 2018 after becoming weakened by honey fungus.
Recently, our Walnut family (Juglandaceae) collection has been sampled by scientists investigating how they make terpenes: essential oils found in their leaves. These chemicals are useful to humans in the perfume industry and for deterring animals which eat plants. Today, species with animal-dispersed fruits such as Walnut (Juglans) and Hickory (Carya) are predominant within the family, while wind-dispersed species like the Caucasian Wingnut are more unusual.