Alnus glutinosa, commonly known as the Common Alder or Black alder is in the same family as the birch: the Betulaceae family.
This low maintenance tree can grow pretty fast, is hardy in US zones 3-7 (UK H7), and has the potential to reach 60 feet (18 m) high in full sun or partial shade (typically reaches around 40 feet (12 m)).
The tree has an upright nature and the canopy can spread out to about 13 to 26 feet (4 to 8 m).
Expect a Common Alder tree to reach its full size in about 20 years in the right conditions – taking up to 50 years in unideal environments.
Alnus glutinosa - Black Alder on a creek line photograph by Oor Woolie.
Suitable locations include use for hedges, rain gardens, and windbreaks. Alnus glutinosa is quick to establish in poorer soils, making it useful for reclamation schemes in areas with wet soils.
If grown on river banks, these deciduous trees can help stabilize the soil.
Its wood is useful for underwater building and smoking fish and coffee.
Black alder can grow in many kinds of soil, such as medium loamy to heavy clay. It can successfully tolerate maritime conditions. It can also grow in nutritionally poor soil but prefers a pH level above 6.
The flowers can be both male and female on the same tree (monoeclous). The winter male catkins and woody cones are ornamentally pleasing and make the black alder easy to identify.
Bees use the pollen from catkins, and birds and small animals feed on the seeds during the winter. Fish also benefit from free food if the trees grow on riverbanks.
The propagation of black alder is very simple.
Seed grown in flats during winter will germinate in the spring if lightly covered with soil.
The young plants can be pricked out and planted in pots to be planted out in permanent locations in summer.
Plants can also be started in spring but should not be covered. They should be left to grow throughout the year and planted the following summer.
Plants can also be propagated from hardwood cuttings taken during dormancy, once leaves have fallen or before new buds have begun to form.
Watch out for pests such as sawflies. Alder sucker (Psylla alni) is commonly seen but rarely causes any issues.
I hope that you enjoyed this guide on how to grow Alnus glutinosa. You may also enjoy the following Gardener's HQ growing guides for plants great to use in screening areas : How to grow Datura and Geum plants.