Alnus rugosa (Du Roi) Spreng.

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Article from Bean's Trees and Shrubs Hardy in the British Isles

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'Alnus rugosa' from the website Trees and Shrubs Online ( Accessed 2019-11-19.


Common Names

  • Speckled Alder


(pl. apices) Tip. apical At the apex.
Lacking hairs smooth. glabrescent Becoming hairless.
Grey-blue often from superficial layer of wax (bloom).
globularSpherical or globe-shaped.
Egg-shaped; broadest towards the stem.
(subsp.) Taxonomic rank for a group of organisms showing the principal characters of a species but with significant definable morphological differentiation. A subspecies occurs in populations that can occupy a distinct geographical range or habitat.
(var.) Taxonomic rank (varietas) grouping variants of a species with relatively minor differentiation in a few characters but occurring as recognisable populations. Often loosely used for rare minor variants more usefully ranked as forms.


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Article from Bean's Trees and Shrubs Hardy in the British Isles

Recommended citation
'Alnus rugosa' from the website Trees and Shrubs Online ( Accessed 2019-11-19.

A shrub or small tree to about 25 ft. Leaves 112 to 4 in. long, oval or ovate, rounded or pointed at the apex, broadly obtuse or rounded at the base, sharply and unevenly double-toothed, glabrous above, downy or glabrous and pale green beneath. Male catkins up to 4 in. long, appearing before the leaves. Female catkins upright, 25 to 35 in. long.

Native of N. America from Newfoundland to British Columbia, also ranging southward on the eastern side of the continent to W. Virginia, Ohio, and Minnesota. It is a hardy shrub of no particular merit, but useful in cold, wet situations. Its close relationship to A. incana, the grey alder of the Old World, is most evident in the following variety:

From the Supplement (Vol. V)

As remarked, this species is closely allied to A. incana. Some botanists include it in A. incana without differentiation, since there seems to be no constant character by which it can be distinguished, except that it is more shrubby. It has also been placed under A. incana as subsp. rugosa (Du Roi) R. T. Clausen, and this is the status accepted by Furlow. The var. americana is not worth recognising, since the leaves of the American race are usually glaucous beneath. The subspecies rugosa is confined to eastern North America, and British Columbia should be deleted from the distribution (see A. tenuifolia).

A. serrulata – This is recognised by Furlow as a distinct species. In addition to the differences mentioned, the buds are more globose and the bark paler, with less prominent lenticels.

A serrulata (Ait.) Willd.

Betula serrulata Ait

A closely allied species, differing chiefly in its leaves, which are usually broadest above the middle and have the margins set with fine, nearly regular teeth. It is confined to the eastern and north-central United States.

var. americana (Reg.) Fern.

A. incana americana Reg.
A. incana var. glauca Loud., not Ait

Leaves glaucous beneath.


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