Betulaceae, the birch family, includes six genera of deciduous nut-bearing trees and shrubs, including the birches, alders, hazels, hornbeams, hazel-hornbeam, and hop-hornbeams numbering a total of 167 species. They are mostly natives of the temperate Northern Hemisphere, with a few species reaching the Southern Hemisphere in the Andes in South America. Their typical flowers are catkins and often appear before leaves.
Alnus glutinosa, the common alder, black alder, European alder, European black alder, or just alder, is a species of tree in the family Betulaceae, native to most of Europe, southwest Asia and northern Africa. It thrives in wet locations where its association with the bacterium Frankia alni enables it to grow in poor quality soils. It is a medium-sized, short-lived tree growing to a height of up to 30 metres (98 feet). It has short-stalked rounded leaves and separate male and female flowers in the form of catkins. The small, rounded fruits are cone-like and the seeds are dispersed by wind and water.
Betula pendula, commonly known as silver birch, warty birch, European white birch, or East Asian white birch, is a species of tree in the family Betulaceae, native to Europe and parts of Asia, though in southern Europe, it is only found at higher altitudes. Its range extends into Siberia, China, and southwest Asia in the mountains of northern Turkey, the Caucasus, and northern Iran. It has been introduced into North America, where it is known as the European white birch or weeping birch and is considered invasive in some states in the United States and parts of Canada. The tree can also be found in more temperate regions of Australia.
Alnus rubra, the red alder, is a deciduous broadleaf tree native to western North America.
Betula nigra, the black birch, river birch or water birch, is a species of birch native to the Eastern United States from New Hampshire west to southern Minnesota, and south to northern Florida and west to Texas. It is one of the few heat-tolerant birches in a family of mostly cold-weather trees which do not thrive in USDA Zone 6 and up. B. nigra commonly occurs in floodplains and swamps.
Alnus incana, the grey alder, tag alder or speckled alder, is a species of multi-stemmed, shrubby tree in the birch family, with a wide range across the cooler parts of the Northern Hemisphere. Tolerant of wetter soils, it can slowly spread with runners and is a common sight in swamps and wetlands. It is easily distinguished by its small cones, speckled bark and broad leaves.
Alnus jorullensis, commonly known as Mexican alder, is an evergreen or semi-evergreen alder, native to eastern and southern Mexico, Guatemala, and Honduras. Although previously reported from the Andes, further collections showed these to be the similar species A. acuminata, commonly found in South America.
Alnus cordata, the Italian alder, is a tree or shrub species belonging to the family Betulaceae, and native to the southern Apennine Mountains and the north-eastern mountains of Corsica. It has been introduced in Sicily, Sardinia, and more recently in Central-Northern Italy, other European countries and extra-European countries, where it has become naturalised.
Alnus nepalensis is a large alder tree found in the subtropical highlands of the Himalayas. The tree is called Utis in Nepali and Nepalese alder in English. It is used in land reclamation, as firewood and for making charcoal.
Myrica rubra, also called yangmei, yamamomo, Chinese bayberry, red bayberry, yumberry, waxberry, or Chinese strawberry is a subtropical tree grown for its fruit.
Mountain alder is a common name for two different alders:
Alnus rhombifolia, the white alder, is an alder tree native to western North America, from British Columbia and Washington east to western Montana, southeast to the Sierra Nevada, and south through the Peninsular Ranges and Colorado Desert oases in Southern California. It occurs in riparian zone habitats at an altitudes range of 100–2,400 metres (330–7,870 ft). While not reported in northern Baja California, it has been predicted on the basis of its climatic adaptation to occur there also. Alnus rhombifolia is primarily found in the chaparral and woodlands, montane, and temperate forests ecoregions.
Alnus acuminata is a species of deciduous tree in the Betulaceae family. It is found in montane forests from central Mexico to Argentina.
Alnus maritima, the seaside alder or brook alder, is a species of shrub or small tree in the family Betulaceae. Alnus maritima is endemic to the United States, and is found naturally in three disjunct populations in Oklahoma, Georgia, and in Maryland and Delaware on the Delmarva Peninsula.
Arocatus roeselii is a species of lygaeid bug.
Frankia alni is a Gram-positive species of actinomycete filamentous bacterium that lives in symbiosis with actinorhizal plants in the genus Alnus. It is a nitrogen-fixing bacterium and forms nodules on the roots of alder trees.
Alnus serrulata, the hazel alder or smooth alder, is a thicket-forming shrub in the family Betulaceae. It is native to eastern North America and can be found from western Nova Scotia and southern New Brunswick south to Florida and Texas.
Alnus alnobetula is a common tree widespread across much of Europe, Asia, and North America. Many sources refer to it as Alnus viridis, the green alder, but botanically this is considered an illegitimate name synonymous with Alnus alnobetula subsp. fruticosa.
Eriophyes laevis is a gall mite which makes small, pimple-like galls on the leaves of alder. The mite was first described by the Austrian zoologist, Alfred Nalepa in 1889 and is found in Europe and North America.
Alnus lusitanica, dubbed the Iberian alder, is a species of flowering plant in the family Betulaceae, native to Portugal and Spain.
