In 1834 Ignaz Tausch described and published the name Alnus x pubescens . It is a hybrid between the two species of deciduous trees, Alnus glutinosa (Black or European Alder) and Alnus incana (Grey Alder). The Hybrid Alder may be found in Austria, Czechoslovakia, Denmark, Finland, France, Germany, Great Britain. Ireland, Italy, Netherlands, North European Russia, Norway, Poland, and Sweden. It has been introduced in Belgium and Central European Russia. These hybrids are difficult to identify because of the overlapping characteristics of their parents. A distinctive feature is that the Hybrid Alder typically has a higher gland density on the undersurface of its leaves than its parents. The undersides of the Hybrid Alder's leaves are downy, particularly along the veins. Young growth is also downy. The parent, Grey Alder, is generally smaller and more shrub-like than the Black Alder. Both parents have green leaves that have a downy or hairy underside. They also have both male and female flowers in the spring. The male flower is a catkin that is narrow and long. The female catkin develops into a cluster of woody cones. The seeds inside the cones are very small samaras. In the fall the seeds ripen and are dispersed by the wind. Both parents may be found in wetlands or along streams or rivers. Both prefer moist soils and can tolerate a wide range of soil types. The tree roots of both species add nitrogen to the soil by forming a relationship with nitrogen-fixing bacteria. The Grey Alder typically grows at higher elevations in central Europe than the Black Alder. Where the Grey and Black Alder overlap they may occasionally form hybrids. This is usually uncommon since they do not flower at the same time. The Grey Alder typically flowers about a week earlier than the Black Alder. The hybrid is a tough, adaptable plant, and has few pest problems. It tolerates short-term flooding. The Hybrid Alder is reportedly very vulnerable and requires protection since this species occurs infrequently in nature.
Curated pairwise relationships between this plant and others in the library — who feeds
whom, who competes, who confuses the pests. Green reads as a good pairing, red as one to avoid.
No curated interactions recorded for this species yet.
Also noted by NC State
Related species the NC State Plant Toolbox flags for this plant — look-alikes to tell
apart, and plants that play a similar role in a planting. Ones we carry in the library are linked.
Full sun (6 or more hours of direct sunlight a day) | Partial Shade (Direct sunlight only part of the day, 2-6 hours)
Soil texture
Loam (Silt)
Soil pH
Acid (<6.0)
Soil drainage
Good Drainage | Moist | Occasionally Wet
Mature size
Height: 20 ft. 0 in. - 30 ft. 0 in. | Width: 10 ft. 0 in. - 20 ft. 0 in.
Canopy layer
2 - Understory (15-40 ft)
Form & Appearance
Habit / form
Rounded
Texture
Medium
Foliage
Deciduous
Leaf color
Green
Leaf type
Simple
Leaf arrangement
Alternate
Leaf shape
Orbicular
Leaf margin
Dentate
Leaf feel
Glossy
Leaf size
1-3 inches long, 1-3 inches wide
Hairs present
Yes
Leaf detail
The leaves are green and orbicular in shape. The margins are dentated. The undersurface of the leaves is hairy, particularly along the leaf veins. There is also a higher gland density on the undersurface.
Flower color
Orange; Red/Burgundy
Flower value
Showy
Flower form
Catkin
Flower detail
The Hybrid Alder produces male and female florets on the same tree. The male florets have clusters of catkins which are reddish-orange, long, and drooping. The female florets are clusters of cone-like catkins.
Bloom time
Spring
Fruit color
Brown/Copper
Fruit type
Samara
Fruit value
Long-lasting
Fruit size
< 1 inch long, < 1 inch wide
Fruit detail
The female catkins develop into wood cones. Inside the cones are winged seeds that are released in the fall when they have matures.
Wildlife & Ecology
Native status
Non-native
Origin
Europe and North European Russia
Distribution
Austria, Belgium, Czechoslovakia, Denmark, Finland, France, Germany, Great Britain. Ireland, Italy, Netherlands, North and Central European Russia, Norway, Poland, and Sweden