As we approach May, many of our native Massachusetts alder (Alnus) species have already reached peak bloom and dropped their flowers.
Luckily, there is still a chance to see the spectacular pendulating catkins (tiny flower clusters) of several later flowering Asiatic alder species along Willow Path. As Curatorial Fellow, I have been evaluating the Arboretum’s alder collection: verifying the nomenclature and identity, collecting specimens for the Cultivated Herbarium, identifying room for growth of the collection, and tracking phenology (life cycle events). One of my personal favorites is a Japanese alder, Alnus maximowiczii, which is currently flowering and shedding an estimated 4 million pollen grains per catkin! Borne 6 months ago as short erect clusters, by spring the male catkins quickly elongate and mature in preparation to flower. On the same branch, you will see the less conspicuous female catkins emerging from their buds. Stay tuned to witness these small female catkins swell and become large cone-like structures (see second image).
A 10 minute stroll on Willow Path starting at the Arborway Gate will present the diversity of the genus Alnus throughout its vast geographic range in the temperate Northern Hemisphere. The best way to spot an alder is to search for the cone-like structures and dangling catkins in the canopy!
–Joyce Cherry, Curatorial Fellow