European Alder/Black Alder
(Alnus glutinosa)
Biological Category
Plants
NY Legal Status
Not Regulated
Species Type
Tree
DESCRIPTION
Black alder is a tree that can grow 60-70 feet tall. The leaf is smooth, 3-5 inches long, with a serrated margin. Small, winged seed is produced in little woody cone-like fruits. The bark is dark brown, with prominent warty strips.
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Leaves: Leaves have a blunt or indented tip. Young leaves are sticky to the touch.
Growth: Grows as a tree as opposed to our native alders which are multi-stemmed shrubs
Habitat: Found in wet areas such as wetlands and along streams or ponds.
Fruit: The fruit, a female catkin, is a small brown woody pine-cone like structure that is visible most of the year. The male catkins are 2 to 4 inches long.
Deliberate release.The seeds float well, traveling efficiently when rivers are flowing rapidly (McVean 1953), and also eaten by various wildlife (Gilman and Watson 1993). It has been widely introduced as an ornamental and for soil stabilization and continues to be promoted even in countries where it is known to be invasive.
Alnus glutinosa establishes readily in wetlands and riparian habitats and forms pure stands or thickets in disturbed wetland sites. It prefers damp or wet ground, often found beside rivers, ponds and canals or in a type of wet woodland called carr, accompanied by willows. Pollination and seed dispersal are by wind. It is relatively variable species and it often hybridizes with other alders.
Alnus glutinosa is a light-demanding species and seedlings do not usually survive in the shade of mature trees. Trees may live up to 100 years, but sometimes on poor sites it may only live for 20-25 years. The presence of symbiotic bacteria in the root nodules enables A. glutinosa to grow on soils that are poor in nitrogen. The root system of specimens growing on flooded soils is differentiated into horizontal roots (with nodules) and the stronger, almost vertical ones that grow deeper.
The oxygen conditions in the roots are also improved by aerenchymatic tissue inside roots which have developed under water. The species is monoecious. Reproduction is mainly by seed, but coppices readily after felling. The seeds are orthodox. Alnus glutinosa grows naturally in various temperate localities with the climate ranging from seasonally cold to warm. Climate data are based on the natural distribution and relevant climatic information.
Alnus glutinosa grows better on flat areas or even in hollows, and it is one of the most suited species for planting on the banks of the lowland rivers, streams, along ditches, lakes and ponds. The altitudinal distribution ranges from sea level (sometimes even below, in depressions) up to high altitude sites, especially in the mountains located in the south of its range.
Dozens of insects and diseases have been observed in association with black alder, but few cause serious damage.
There are no known biological control methods for this species.
Pulling / Digging Up: Trees should be felled and then herbicide applied to the stumps to prevent sprouting.
Effective herbicides include napropamide (preemergence), glyphosate via exposed stump application triclopyr triethylamine via foliar application.
Alnus glutinosa can be successfully controlled by a combination of physical and chemical means. Trees are often felled and the stumps treated with herbicides. However, follow-up procedures are necessary as A. glutinosa is known to resprout. A. glutinosa is not affected by low rates of the pre-emergence herbicide pendimethalin but is damaged by higher concentrations (2.0 kg a.i. ha–1) and above), as well as by napropamide.
Other effective herbicides include glyphosate (stump treatment) and triclopyr triethylamine (foliar application).
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