OregonFlora: Alnus glutinosa vs. Betulaceae

	Alnus glutinosa	Betulaceae
	European black alder	birch family
Habit		Shrubs or trees deciduous.
Leaves		alternate; simple, pinnately veined; margins toothed; stipules present, often deciduous.
Inflorescences		unisexual, emerging before leaves; male and female on same plant, staminate flowers in pendent catkins, 1–3 near tips of previous years’ twigs; immature catkins formed the fall before flowering in most taxa, pistillate flowers in catkins or solitary in leaf axils.
Flowers		radially symmetric.
Staminate flowers		calyces absent or of about 4 tiny; scale-like sepals; corollas absent; stamens mostly 4–6; free; pistillodes present or absent.
Pistillate flowers		calyces rudimentary or absent; corollas and staminodes absent; ovaries inferior, with 2 locules that are usually united above; placentation axile; styles 2 (sometimes united basally).
Fruits		nuts or tiny 2-winged samaras, surrounded by bracts; either grouped into cone-like infructescences (Alnus and Betula) or 1–3 together (Corylus).

	Alnus glutinosa	Betulaceae
Distribution	[WildflowerSearch map] [BONAP county map]	[BONAP county map]
Discussion		Northern Hemisphere, South America. 6 genera; 3 genera treated in Flora. Betulaceae form an important part of the woody vegetation in many parts of Oregon. Many species are tolerant of flooding, waterlogging, and cold, and they are a common component of the woody cover on streambanks and wet bottomlands, especially in the mountains. Some are very tolerant of disturbance, and they are often found on recently logged sites. The seeds of all our species are eaten by birds and other wildlife.
Source		Flora of Oregon, volume 2, page 379
Sibling taxa	A. alnobetula, A. incana, A. rhombifolia, A. rhombifolia x Alnus rubra, A. rubra
Web links	Local floras: OR, WA Local Web sites: Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search	Local floras: CA, OR Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Betulaceae

European black alder

birch family

Habit

Shrubs or trees deciduous.

Leaves

alternate; simple, pinnately veined;

margins toothed;

stipules present, often deciduous.

Inflorescences

unisexual, emerging before leaves; male and female on same plant, staminate flowers in pendent catkins, 1–3 near tips of previous years’ twigs; immature catkins formed the fall before flowering in most taxa, pistillate flowers in catkins or solitary in leaf axils.

Flowers

radially symmetric.

Staminate flowers

calyces absent or of about 4 tiny; scale-like sepals;

corollas absent;

stamens mostly 4–6; free; pistillodes present or absent.

Pistillate flowers

calyces rudimentary or absent;

corollas and staminodes absent;

ovaries inferior, with 2 locules that are usually united above;

placentation axile;

styles 2 (sometimes united basally).

Fruits

nuts or tiny 2-winged samaras, surrounded by bracts; either grouped into cone-like infructescences (Alnus and Betula) or 1–3 together (Corylus).

Alnus glutinosa

Betulaceae

Distribution

[WildflowerSearch map]

[BONAP county map]

Discussion

Northern Hemisphere, South America. 6 genera; 3 genera treated in Flora.

Betulaceae form an important part of the woody vegetation in many parts of Oregon. Many species are tolerant of flooding, waterlogging, and cold, and they are a common component of the woody cover on streambanks and wet bottomlands, especially in the mountains. Some are very tolerant of disturbance, and they are often found on recently logged sites. The seeds of all our species are eaten by birds and other wildlife.

Source

Flora of Oregon, volume 2, page 379

Sibling taxa

A. alnobetula, A. incana, A. rhombifolia, A. rhombifolia x Alnus rubra, A. rubra

Web links