Practical ecological knowledge for the temperate reader.

Alnus Sp. - Alder

Family: Betulaceae (Birch Family) [E-flora]

"Stem: trunk < 35 m; bark smooth, gray to brown; twigs glabrous to fine-hairy, red-gray; lenticels small; winter buds stalked, 0–6-scaled. Leaf: glabrous to fine-hairy; blade 3–15 cm, cordate to elliptic or diamond-shaped. Staminate inflorescence: 5–20 cm; bracts each subtending 3 flowers, 4 bractlets. Pistillate inflorescence: 5–20 mm; bracts each subtending 2 flowers, 4 fused bractlets. Staminate flower: sepals 4; stamens 1–4. Pistillate flower: sepals 0. Fruit: many, in cone-like catkin, not enclosed by bract, winged, bracts 3 mm, woody, persistent." [Jepson]

"+/- 25 species: northern hemisphere, South America. (Latin: alder) Root nodules contain nitrogen-fixing bacteria; wood used for interior finishing, to smoke fish, meats." [Jepson]

Local Species

Identification and Taxonomic Notes

1. Leaves finely once or twice saw-toothed; axillary buds unstalked, pointed; male catkins unstalked; stalks as long as or longer than the conelike sillicles..........................Alnus viridis
1. Leaves coarsely to irregularly round-toothed; axillary buds pedunculate, blunt or short-pointed; male catkins stalked; stalks shorter than the conelike silicles
2. Leaf margins rolled under; nutlets with narrow-winged margins.......................................Alnus rubra
2. Leaf margins not rolled under; nutlets wingless..................................Alnus incana [E-flora]

Medicinal Use

Alnus sp (BETULACEAE) Astringent; Inflammation; Throat; Wound [Duke]

Mountain Alder - Alnus tenuifolia

"Alnus tenuifolia is a deciduous Tree growing to 9 m (29ft 6in) at a fast rate. It is hardy to zone (UK) 2. It is in flower in March, and the seeds ripen in October. The flowers are monoecious (individual flowers are either male or female, but both sexes can be found on the same plant) and are pollinated by Wind.It can fix Nitrogen. Suitable for: medium (loamy) and heavy (clay) soils and can grow in heavy clay and nutritionally poor soils. Suitable pH: acid, neutral and basic (alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist or wet soil." [PFAF]

Status: Native.[E-flora]

Subtaxa Presnt in B.C.

"General: Deciduous shrub or tree, up to 12 m tall, usually 2-5 m tall, new growth short-hairy; axillary buds with short stalks; bark scaly, often lichen-covered, yellowish-brown or grey." [IFBC-E-flora]
"Leaves: Alternate, deciduous, smooth, coarsely to irregularly toothed, the teeth pointing outwards, leaf margins not rolled under, brownish in the fall." [IFBC-E-flora]
"Flowers: Inflorescence of male and female catkins, which open before the leaves on previous year's growth; male catkins with stalks." [IFBC-E-flora]
"Fruits: Small nutlets, without wings; female cones 1-1.5 cm long, egg-shaped." [IFBC-E-flora]

"Habitat / Range Moist forests, streamsides, bogs and fens in the montane zone; common in BC east of the Coast-Cascade Mountains; N to AK, YT and NT, E to SK, and S to NM, AZ and CA." [IFBC-E-flora]



Cultivation details
"Prefers a heavy soil and a damp situation[1, 11]. Grows well in heavy clay soils[11]. Tolerates very infertile sites[200]. A fast-growing but short-lived tree[229]. There is some confusion over the correct name of this tree with one authority citing the European species A. incana as the correct name[60]. Another report says that this species is closely related to A. incana, but distinct[229]. Some modern works treat it as a subspecies (Alnus incana tenuifolia). This species has a symbiotic relationship with certain soil micro-organisms, these form nodules on the roots of the plants and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[200]." [PFAF]

"Seed - best sown in a cold frame as soon as it is ripe and only just covered[200]. Spring sown seed should also germinate successfully so long as it is not covered[200, K]. The seed should germinate in the spring as the weather warms up. When large enough to handle, prick the seedlings out into individual pots. If growth is sufficient, it is possible to plant them out into their permanent positions in the summer, otherwise keep them in pots outdoors and plant them out in the spring. If you have sufficient quantity of seed, it can be sown thinly in an outdoor seed bed in the spring[78]. The seedlings can either be planted out into their permanent positions in the autumn/winter, or they can be allowed to grow on in the seed bed for a further season before planting them. Cuttings of mature wood, taken as soon as the leaves fall in autumn, outdoors in sandy soil."[PFAF]


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