Trees 

Caucasian Alder

Alnus subcordata
Betulaceae (Birch family)
As the common name suggests, Alnus subcordata is native to the Caucasus Mountains but clearly enjoys our Cambridge climate. It now towers over the Birch collection, measuring a mighty 17.5m, making it one of our champion trees.
The attractive, crumbly-textured slender male catkins appear exceptionally early, often by mid-December or early January.