The alder has a great diversity of species. However, there are only three varieties in Germany. Could you tell the black alder from its relatives, the green alder or the gray alder, based on the leaves? The distinction between non-native species is probably even more difficult. Don't worry, in the following article you will read all about the characteristics of the different types of alder. In addition, you will learn a lot about other properties that characterize the deciduous tree.
How do I recognize the leaves of the black alder, green alder and gray alder?
The leaves of the black alder are egg-shaped with a serrated leaf edge and green in color. In comparison, the green alder has heart-shaped, asymmetrical and dark green leaves, while the leaves of the gray alder are ovate, gray hairy and double-serrated.
General characteristics
- The alder is a deciduous tree
- summergreen
- rich green color
- often egg-shaped
Characteristics of the leaves of different alder species
Alnus Company Erle
- sawn leaf edge
- ovoid
- green
- fest
- protruding spikes on the edge of the leaf
Oriental Alder
- obovate
- long petiole
- green
- small indentations in the edge of the leaf
- wavy leaf edge
Gray Alder
- ovoid
- pointed
- Leaf edge is coarse and double serrated
- gray, felty hairs on the underside of the leaves
- up to 10 cm long
Purple Alder
- large-leaved
- tapering
- dark green
- ovoid
- The underside of the leaf is very dull, lighter than the top of the leaf
- sawn leaf edge
Heart-leaved alder
- comparatively small
- Leaf edge is slightly sawn
- dark green
- asymmetrical
Red Alder
- ovoid
- tapering
- about 15 cm long
- alternate leaf position
- sawn leaf edge
Special features
Did you know that the alder is the only deciduous tree that sheds its leaves when they are green? This is possible because alder trees enter into a symbiosis with so-called root nodules. These are bacteria for which the alder tree provides a breeding ground, while the bacteria supply the tree with nitrogen compounds so that it can grow successfully even on nutrient-poor soils. Alder trees are therefore also called pioneer trees because they have adapted to locations in inhospitable locations. Furthermore, alder trees provide a food source and habitat for numerous butterfly species.
Indications of diseases
So don't be surprised if you find green leaves under your alder tree. This is not a sign of illness. However, you should pay attention if the leaves become unusually light and have a yellowish discoloration. In addition, when a tree is infected with fungus, it only produces very small new leaves or no new leaves at all. Old leaves are also shed prematurely. If you observe these symptoms, you are probably dying of alder shoots.
