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Hybrid Alder Alnus x pubescens

Previously known as:

  • Alnus balatonialis
  • Alnus glutinosa var. pubescens
  • Alnus × hybrida
  • Alnus incana var. glabrescens
  • Alnus x ambigua
  • Alnus x beckii
  • Alnus x montana
  • Alnus x spuria
  • Alnus x tauschiana
Phonetic Spelling
AL-nus BI pew-BES-ens
Description

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.

 

See this plant in the following landscape:
Cultivars / Varieties:
Tags:
#deciduous#wet sites#flooding#adaptable#single trunk#poor soils tolerant
 
Cultivars / Varieties:
Tags:
#deciduous#wet sites#flooding#adaptable#single trunk#poor soils tolerant
  • Attributes:
    Genus:
    Alnus
    Family:
    Betulaceae
    Life Cycle:
    Woody
    Country Or Region Of 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
    Dimensions:
    Height: 20 ft. 0 in. - 30 ft. 0 in.
    Width: 10 ft. 0 in. - 20 ft. 0 in.
  • Whole Plant Traits:
    Plant Type:
    Tree
    Woody Plant Leaf Characteristics:
    Deciduous
    Habit/Form:
    Rounded
    Texture:
    Medium
  • Cultural Conditions:
    Light:
    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
    USDA Plant Hardiness Zone:
    3b, 3a, 4b, 4a, 5b, 5a, 6b, 6a
  • Fruit:
    Fruit Color:
    Brown/Copper
    Fruit Value To Gardener:
    Long-lasting
    Display/Harvest Time:
    Fall
    Fruit Type:
    Samara
    Fruit Length:
    < 1 inch
    Fruit Width:
    < 1 inch
    Fruit Description:
    The female catkins develop into wood cones. Inside the cones are winged seeds that are released in the fall when they have matures.
  • Flowers:
    Flower Color:
    Orange
    Red/Burgundy
    Flower Inflorescence:
    Catkin
    Flower Value To Gardener:
    Showy
    Flower Bloom Time:
    Spring
    Flower Description:
    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.
  • Leaves:
    Woody Plant Leaf Characteristics:
    Deciduous
    Leaf Color:
    Green
    Leaf Feel:
    Glossy
    Leaf Type:
    Simple
    Leaf Arrangement:
    Alternate
    Leaf Shape:
    Orbicular
    Leaf Margin:
    Dentate
    Hairs Present:
    Yes
    Leaf Length:
    1-3 inches
    Leaf Width:
    1-3 inches
    Leaf Description:
    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.
  • Stem:
    Stem Is Aromatic:
    No
  • Landscape:
    Landscape Location:
    Coastal
    Pond
    Riparian
    Landscape Theme:
    Rain Garden
    Winter Garden
    Resistance To Challenges:
    Insect Pests
    Poor Soil
    Wet Soil