Most landscape designers have favorite trees and I am no exception. My list of favorites has varied over the years but Alnus glutinosa always has a prominent spot on the list.
While black alder is widely known in the landscape industry it is still not routinely used. Perhaps it is because although the tree is ornamental it has a non-descript flower. Or maybe it’s because the tree has been referenced as best used in a bio-mass planting. It’s difficult to pinpoint why it has never caught on with designers and homeowners based on its many positive characteristics
It fixes atmospheric nitrogen which means it NEVER requires fertilizer to look lush, green and healthy. That alone should make it desirable.
But black alder has an even more interesting feature. It is the only deciduous tree I know that bears a “pine cone”. The small female cones are called strobiles or nutlets and have incredible fall/winter character. They make quite a show from September through spring in persistent clusters.
Black alder is most commonly found grown as a multi-stem tree. It matures at about 40’ high and 25’ wide here in northern Illinois. The bark on younger trees is a soft gray. Frequently I will substitute alder for river birch in my landscape designs since it will tolerate very wet areas, but it is also adaptable to dry areas.
Again, I cannot say with certainty why black alder has not charmed more people with its beauty, but I heartily endorse it for more widespread applications in the residential landscape.