The largest species are red alder ( A. rubra ) on the west coast of North America, and black alder ( A. glutinosa ), native to most of Europe and widely introduced elsewhere, both reaching over 30 m. By contrast, the widespread Alnus viridis ( green alder ) is rarely more than a 5 m tall shrub.

Native Americans used red alder bark ( Alnus rubra ) to treat poison oak, insect bites, and skin irritations.

menziesii ), Pacific madrone ( Arbutus menziesii ), Red alder ( Alnus rubra ) and Bigleaf maple ( Acer macrophyllum ) forest.

They often form large thickets, and thrive in the open spaces under stands of Red Alder ( Alnus rubra ).

Alnus rubra, the red alder, is a deciduous broadleaf tree native to western North America.

Alnus rubra grows from southeast Alaska south to central coastal California, nearly always within about 200 km of the Pacific coast, except for an extension 600 km inland across northern Washington into northernmost Idaho.

In moist forest areas Alnus rubra will rapidly cover a former burn or clearcut, temporarily preventing the growth of conifers but also improving soil fertility for future growth of conifers.

Alnus rubra is also very valuable for playing host to the nitrogen fixing actinomycete Frankia.

Native Americans used red alder bark ( Alnus rubra ) to treat poison oak, insect bites, and skin irritations.

Alnus rubra is an important forestry tree.

Alnus rubra are planted as ornamental trees and will do well in wet swales, riparian areas, or on stream banks.

Alnus rubra are known for growing easily in burned or destroyed land, and are used as " pioneering " or " reclamation " trees.

* Flora of North America: Alnus rubra

* Plants of British Columbia: Alnus rubra

* Jepson Flora: Alnus rubra

* USDA Plants Profile: Alnus rubra

* Interactive Distribution Map of Alnus rubra

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fr: Alnus rubra

Trees in the Arboretum include: Acacia dealbata, Acer campestre, Acer negundo, Acer paxii, Acer saccharinum, Aesculus x carnea, Agathis robusta, Alnus rhombifolia, Angophora costata, Araucaria bidwillii, Archontophoenix cunninghamiana, Baphia chrysophylla, Bauhinia forficata, Bauhinia variegata, Betula nigra, Brachychiton acerifolius, Brachychiton acerifolius ( Herman hybrid ), Brachychiton discolor, Brachychiton populneus, Brahea armata, Brahea brandegeei, Brahea edulis, Butia capitata, Calocedrus decurrens, Calodendrum capense, Caryota urens, Castanospermum australe, Casuarina cunninghamiana, Cedrus deodara, Cedrus libani, Celtis australis, Chamaerops humilis, Chionanthus retusus, Chorisia insignis, Chorisia speciosa, Cryptocarya rubra, Cryptomeria japonica, Cupaniopsis anacardioides, Cupressus glabra, Cupressus sp., Dalbergia sissoo, Dracaena draco, Ehretia anacua, Ehretia tinifolia, Eriobotrya deflexa, Eriobotrya japonica, Erythrina coralloides, Erythrina falcata, Erythrina humeana, Eucalyptus camaldulensis, Eucalyptus citriodora, Eucalyptus cladocalyx, Eucalyptus globulus, Eucalyptus robusta, Eucalyptus rudis, Eucalyptus viminalis, Ficus microcarpa nitida, Ficus racemosa, Ficus religiosa, Ficus sp., Fraxinus uhdei, Fraxinus velutina, Heteromeles arbutifolia, Jacaranda acutifolia, Jubaea chilensis, Juglans nigra, Lagerstroemia indica, Liquidambar formosana, Liriodendron tulipifera, Livistona australis, Livistona chinensis, Macadamia ternifolia, Magnolia grandiflora, Metasequoia glyptostroboides, Metrosideros excelsa, Myrcia cauliflora, Nyssa sylvatica, Phoenix canariensis, Phoenix dactylifera, Phoenix reclinata, Phoenix reclinata ( hybrid ), Phoenix roebelenii x rupicola, Phoenix rupicola, Phytolacca dioica, Pinus canariensis, Pinus edulis, Pinus halepensis, Pinus thunbergii, Pittosporum phillyraeoides, Pittosporum tenuifolium, Pittosporum undulatum, Podocarpus gracilior, Podocarpus totara, Psidium guajava, Quercus agrifolia, Quercus alba, Quercus cerris, Quercus coccinea, Quercus macrocarpa, Quercus palustris, Quercus rubra, Quercus suber, Quercus virginiana, Rhapidophyllum hystrix, Rhapis excelsa, Rhodosphaera rhodanthema, Rhopalostylis baueri, Rhus integrifolia, Sabal causiarum, Sabal sp., Salix babylonica, Schinus molle, Schinus polygamus, Sequoiadendron giganteum, Syagrus romanzoffiana, Tabebuia avellanedae, Taxodium distichum, Tipuana tipu, Toona ciliata, Trachycarpus fortunei, Trachycarpus wagnerianus, Tristania laurina, Trithrinax acanthocoma, Ulmus americana, Umbellularia californica, Washingtonia filifera, Washingtonia robusta, and Zelkova serrata.

Alnus rubra | Red Alder forest near Sky Country Trailhead

* Alnus acuminata — Andean alder, Andes Mountains, South America

* Alnus cordata — Italian alder, Italy

* Alnus firma — Kyūshū ( Japan )

* Alnus glutinosa — black alder, Europe

* Alnus incana — grey alder, Eurasia

* Alnus japonica — Japanese alder, Japan

* Alnus jorullensis — Mexican alder, Mexico, Guatemala ( one of the few evergreen species )

* Alnus mandshurica — Russian Far East, China, Korea

* Alnus matsumurae — Honshū ( Japan )

* Alnus nepalensis — Nepalese alder, eastern Himalaya, southwest China

* Alnus orientalis — Oriental alder, southern Turkey, northwest Syria, Cyprus

* Alnus pendula — Japan, Korea

* Alnus rhombifolia — white alder, interior western North America

* Alnus serrulata — hazel alder, tag alder or smooth alder, eastern North America

* Alnus sieboldiana — Honshū ( Japan )

* Alnus subcordata — Caucasian alder, Caucasus, Iran

* Alnus trabeculosa — China, Japan

* Alnus formosana — Formosan alder, Taiwan

* Alnus maritima — seaside alder, east coastal North America, plus disjunct population in Oklahoma

* Alnus nitida — Himalayan alder, western Himalaya

* Alnus viridis — green alder, widespread: