Alnus incana – Grey Alder (central Europe)
Habit: Medium-size tree or large shrub, (4) 8-12 (20) m tall, 3-6 m wide; asymmetrically loose, conical, almost like a thicket, branches slightly lilting to vertically upright, fast-growing, 30-60 cm a year.
Flowers: Yellow catkins in March.
Leaves: Pointedly ovoid, dull green, whitish to bluish green underneath.
Roots: Shallow and far-reaching, very intense; forms runners when roots are damaged; tolerates floods and covering; collect nitrogen.
Demands: Sun to light shade; for cold to moderately warm areas, very frost hardy; wind resistant.
Soil: Damp to moderately dry, all chalky substrates; resistant to all mechanical damage; tolerant of salt.
Hardiness: Zone 2