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Betulaceae
Betulaceae Distribution Birch family. Family with 6 genera about 170 species. Distributed worldwide in northern temperate areas as well as South American mountains. Important members Alnus – Alder Betula – Birch Carpinus – Hornbeam Corylus – Hazels Ostrya – Hop hornbeams Betulaceae Family Characteristics Temperate trees and shrubs. Betulaceae Family Characteristics Leaves are simple, deciduous and alternate. Betulaceae Family Characteristics Flowers unisexual catkins with male and female flowers on the same plant. Female flowers Male flowers Male flowers Female flowers Alder (Alnus) Betulaceae Family Characteristics Fruits are a single-seeded nut. Some seeds have a wing for wind dispersal. Betula Carpinus Betulaceae Economic uses Landscape ornamentals Timber Nut crop - Hazel Hazelnut (Corylus) Betulaceae Alnus glutinosa – European black alder European black alder is a medium-sized tree that is an excellent choice for extremely wet areas, although it does well in drier soils as well. It is native to Europe and western Asia and has naturalized in wet areas of North America. Alnus comes from Latin as “al” for near and “nus ” for water. Betulaceae Alnus glutinosa – European black alder Growth habit: Medium –sized trees are pyramidal and can be grown with a single or multiple trunks. Tree size: Height ranges to 60 feet and 30 feet wide. Betulaceae Alnus glutinosa – European black alder Flowers: Male and female flowers are separate on the same plant. Male flowers are up to 4-inch catkins hang at the terminal of the branch. Female flowers Brown catkins open to shed yellow pollen before the leaves emerge. Female flowers are reddish-brown and egg-shaped. Male flowers Betulaceae Alnus glutinosa – European black alder Fruit: The fruit is a small winged nutlet borne in a globose 1/2-inch-long woody pine cone-like dry catkin. The fruit matures and is wind disseminated in late autumn and the dry catkin persists through winter. Betulaceae Alnus glutinosa – European black alder Leaf - Leaves are alternate, simple, up to 4 inches long. The leaf margin is doubly serrate and the leaf tip has a deep notch (obcordate). Leaves are a dark, green in summer, and green or brown in autumn. Notch Betulaceae Alnus glutinosa – European black alder Buds: The buds are rounded and produced on an obvious short stalk. Short stalk Betulaceae Alnus glutinosa – European black alder Culture: Full sun or part shade. Plants do well in wet areas. It also does well in infertile areas because plants have the ability to fix nitrogen. They are adaptable to a range of soil types and pH. Hardy in zones 7 to 4. Betulaceae Alnus glutinosa – European black alder Cultivars: ‘Laciniata’ is a popular cut leaf form that presents a finer texture than the species, especially in young trees. Betulaceae Alnus glutinosa – European black alder Cultivars: ‘Imperials’ has extremely deeply cut leaves, even more so than ‘Laciniata’. Betulaceae Betula nigra – River birch River birch has become a very popular medium-sized tree. It is native to Eastern North America including Kentucky. It naturally occurs along moist stream banks. Betulaceae Betula nigra – River birch River birch can be used as a screen or shade tree, and as a street tree with irrigation. River birches are attractive when planted in groups, especially against a dark background. Betulaceae Betula nigra – River birch River birch can be grown with a single trunk or as a multiple trunk tree. Multiple trunks are best utilized in groups of three rather than two or four. Betulaceae Betula nigra – River birch Growth habit - Pyramidal when young, oval at maturity with an irregular crown. Tree size: 40 to 70 feet tall, can reach 90 feet, with a 40- to 60-foot spread. Young plants have attractive peeling bark. Betulaceae Betula nigra – River birch Young trees can have peeling bark, but older trees tend to have a graybrown flaky or furrowed bark. Betulaceae Betula nigra – River birch Flower – Male flowers are up to 3-inch long, catkins that are clustered at the tips of the branches and drooping. Female flowers are small catkins with stigma that extend between the scales. Female flowers Female flowers Male flowers Betulaceae Betula nigra – River birch Fruit – The fruit is a small nutlet in a 1 to 2-inch long pendulous catkin. Fruit ripens in spring and the winged nutlets are wind dispersed. Catkin Winged nutlets Nutlet Betulaceae Betula nigra – River birch Leaf - Alternate, simple, up to 4 inches long and 2 inches wide. Leaf margin is doubly serrate. Doubly serrate Leaf shape is deltoid to rhombic. Betulaceae Betula nigra – River birch Leaf – Leaf color is medium to dark green in summer, leaves turn yellow in fall, but they drop quickly and therefore do not provide a significant autumn display. Betulaceae Betula nigra – River birch Culture: Full sun or part shade. River birch likes moist, fertile soil with a pH of 6.5 or less. It is short-lived in urban areas, lasting 30 to 40 years. It lives longer when planted in moist areas. Betulaceae Betula nigra – River birch Culture: River birch is the most troublefree of the birches with little insect or disease problems. It is resistant to bronze birch borer and leaf miner. Betulaceae Betula nigra – River birch Culture: River birch can develop iron chlorosis if planted in high pH soils. Betulaceae Betula nigra – River birch Culture: In some years, leaf spot and aphids can be a problem. Leaf spot Aphids Betulaceae Betula nigra – River birch Culture: River birch is prone to ice storm damage. Betulaceae Betula nigra – River birch Uses: Even without the white bark of youth, large river birch can be effective shade trees with filtered sunlight that permits growth of other plants beneath the canopy as long as the soil does not dry out. Betulaceae Betula nigra – River birch Uses: River birch is often used as a single specimen plant, but it is also very effective when planted in mass and limbed-up to expose the exfoliating bark. Repeating the three trunk groupings of spaced trees in a curvilinear pattern works to follow the building’s pattern and buffer pedestrian traffic walkway from the man-made structure. Betulaceae Betula nigra – River birch Cultivars: Dura-Heat (‘BNMTF’) is a cultivar selected for its white bark coloration and good heat tolerance for southern landscapes. It also shows good tolerance to aphids and leaf spot. Betulaceae Betula nigra – River birch Cultivars: Heritage (‘Cully’) is possibly the most planted river birch cultivar. It is a vigorous grower selected for good white flaky bark. Heritage is a much better choice than seedlinggrown river birch. Seedlings are slower growing with variable bark coloration. Young bark color. Older bark color. Betulaceae Betula nigra – River birch Cultivars: Fox Valley (‘Little King’) is a smaller, slower growing selection with a rounded habit. Betulaceae Betula nigra – River birch Cultivars: Tecumseh Compact is another compact, slower growing selection with arching branches. Betulaceae Betula nigra – River birch Cultivars: ‘Summer Cascade’ is a weeping form that is usually grafted onto a standard. It is a graceful plant that can get 15 feet tall. Betulaceae Betula pendula – European white birch European white birch is an exceptionally ornamental mediumsized tree prized for its pendulous growth and white bark. Unfortunately, it is short-lived because of its susceptibility to bronze birch borer. In most landscapes, European white birch has been replaced with white barked river birch cultivars that are resistant to the borer. Native to Northern Europe. Betulaceae Betula pendula – European white birch Growth habit - Pyramidal when young, then becoming oval pyramidal to oval at maturity. Branches are pendulous. Tree size: 40 to 50 feet tall with a 20 foot spread. Betulaceae Betula pendula – European white birch Female flowers Flower - Male flowers are up to 3 inches long as a slender, catkin drooping in the leaf axils. Female flowers are cylindrical, narrow catkins up to 1 inch long. Male flowers Betulaceae Betula pendula – European white birch Fruit – The fruits are small nutlets enclosed in a pendulous catkin that ripens in autumn, but may not shed the winged fruits until the following spring. Current season’s female flowers Last season’s fruits Betulaceae Betula pendula – European white birch Leaf - Alternate, simple leaves are diamond-shaped and up to 3 inches long with a tapering tip. Leaves, which are doubly serrate, are a lustrous dark green in summer and yellow or yellow-green in fall. Betulaceae Betula pendula – European white birch Bark – Bark on young trees is an attractive white, turning almost black with age. Betulaceae Betula pendula – European white birch Culture: Full sun. European white birch tolerates dry soils but grows best in moist, welldrained sandy or loamy soils. Irrigation should be used during drought conditions to prevent stress that can make trees more susceptible to insect attack. Hardy in zones 6 to 2. Betulaceae Betula pendula – European white birch Culture: Bronze birch borer is a major pest on white barked birches and is especially bad on European white birch. The first signs of the insect is terminal branch die-back. The insect eventually kills the tree. Betulaceae Betula pendula – European white birch Culture: Birch leaf miner is also a significant insect pest on European white birch. A fly lays eggs on emerging leaves and the larvae tunnels between the leaf layers. Betulaceae Betula pendula – European white birch Cultivars (several): ‘Gracilis’ is a popular cultivar with finely cut leaves and drooping branches. Betulaceae Betula pendula – European white birch Cultivars: Purple Rain (‘Monte’) is the purple rain weeping birch. It has lustrous purple foliage and slightly pendulous branches. Betulaceae Betula pendula – European white birch Cultivars: ‘Youngii’ is a common cultivar that is a slow-growing, spreading form, reaching a height of 15 to 20 feet with a spread of 20 to 25 feet. Betulaceae Betula pendula – European white birch Cultivars : ‘Tristis’- Slow growing plant with crooked branches that hang down from a central leader. There are massive plants in Europe that are very impressive. Betulaceae Carpinus betulus – European hornbeam European hornbeam is larger than American hornbeam, with larger leaves and a spreading form that tends to make it grow as wide as it is tall. It is grown more than any other non-native hornbeam. Betulaceae Carpinus betulus – European hornbeam Growth habit - Pyramidal when young, oval-rounded or rounded when mature. Fine textured. Tree size: 40 to 60 feet tall and 30 to 40 feet wide; can reach a height of 70 to 80 feet. Betulaceae Carpinus betulus – European hornbeam Flowers - Male and female flowers are produced separately on the same plant in pendulous catkins. Female flowers Female flowers Male flowers Betulaceae Carpinus betulus – European hornbeam Fruit – The fruit is a small nutlet located at the base of a two to three-lobed bract. Paired fruits hang in pendulous clusters. Fruits mature in September to October. Bract Nutlet Bract Betulaceae Carpinus betulus – European hornbeam Leaf - Alternate, simple, up to 5 inches long and 2 inches wide. Autumn color is bronze to yellow. Betulaceae Carpinus betulus – European hornbeam Leaf – The tip of the leaf narrows to a point and the leaf margin is sharply doubly-serrate. The leaf veins on the upper surface are ridged giving a wave-like appearance. Betulaceae Carpinus betulus – European hornbeam Buds – Lateral buds are sharply pointed and often curve around the stem. The overlapping (imbricate) scales have straight pubescent hairs. Betulaceae Carpinus betulus – European hornbeam Trunk – The bark on older plants is gray and can be wonderfully fluted and muscled. Betulaceae Carpinus betulus – European hornbeam Culture: Full sun or partial shade. European hornbeam does well in all soil textures and can handle alkaline and acidic situations. It can handle moderate to difficult city environments. Hardy in zones 7 to 5. Betulaceae Carpinus betulus – European hornbeam European hornbeam tolerates pruning very well and can be used for hedging and screens. It is a common hedging plant, especially in European gardens. Betulaceae Carpinus betulus – European hornbeam European hornbeam makes a great aerial hedge, similar to the way European beech (Fagus sylvatica) is used. This is a great way to show off the fluted, pale gray trunks and to define spaces in a formal garden design. Betulaceae Carpinus betulus – European hornbeam European hornbeam is used in this aerial hedge at Dumbarton Oaks in Georgetown. It is a particularly good choice because it frames the outdoor room and provides interest along the path with its muscle-like trunk structure. Betulaceae Carpinus betulus – European hornbeam One of the most impressive uses of European hornbeam is at the Queen’s Garden at Het Loo in the Netherlands. There is a pleached arbor of European hornbeam trained over a tunneled corridor complete with windows. Betulaceae Carpinus betulus – European hornbeam Cultivars: ‘Fastigiata’ is a commonly grown dense, compact tree that is narrow when young, becoming oval with age. It does not maintain a central leader as it ages. Betulaceae Carpinus betulus – European hornbeam Cultivars: ‘Columnaris’ is similar to ‘Fastigiata’ but it tends to form an oval or egg-shape because it maintains a central leader. It can grow 30 feet tall and wide. Betulaceae Carpinus betulus – European hornbeam Cultivars: ‘Globosa’ is another slow growing upright plant with a rounded form. It is densely twiggy near the outline of the plant. Slower growing than ‘Fastigiata’. Betulaceae Carpinus betulus – European hornbeam Cultivars: ‘Franz Fountaine’ is a narrow, columnar tree that can grow 35 feet tall and 15 feet wide, it is the most narrow European hornbeam cultivar. Betulaceae Carpinus betulus – European hornbeam Cultivars: ‘Pendula’ is an irregular weeping form. Large plants are very impressive . Old specimens can be 30 feet tall and twice as wide. Betulaceae Carpinus caroliniana – American hornbeam American hornbeam is a good specimen tree and is a wonderful addition to a natural landscape. The trunk and branches of this tree have ridges that look like muscles. Native along stream beds in North America from Canada to Florida, west to Texas. It is not as commercially available as European hornbeam. Betulaceae Carpinus caroliniana – American hornbeam Growth habit - Pyramidal when young, plants become rounded to spreading with age. Trees are usually low branched unless pruned. Tree size: 20 to 30 feet tall and 30 feet wide, but can get larger. Betulaceae Carpinus caroliniana – American hornbeam Flowers - Male and female flowers are produced separately on the same plant in pendulous catkins that appear in April. Female flowers Male flowers Female flowers Male flowers Betulaceae Carpinus caroliniana – American hornbeam Fruit – The fruit is a nutlet located at the base of the yellow to reddish lobed bract. The paired fruit are held in loose pendulous clusters. The fruit matures in September to October. Nutlet Bracts Nutlets Betulaceae Carpinus caroliniana – American hornbeam Leaf - Alternate, simple, up to 5 inches long and 2 inches wide. Autumn color is yellow to orange-red. Betulaceae Carpinus caroliniana – American hornbeam It can be difficult to distinguish American and European hornbeams. Several of the key features besides fall leaf color include leaf and bud characters. Leaves – Leaves of both European and American hornbeam are doubly-serrate with European hornbean tending to be more sharply serrate. Carpinus caroliniana European hornbeam tends to have more branching leaf veins leading to the serrate tips (arrow). Carpinus betulus Betulaceae Carpinus caroliniana – American hornbeam Leaves – The veins on the undersides of both the European and American hornbeams have pubescence. In the American hornbeam the hairs are tufted in the axils of the main veins, while in European hornbean the hairs are straight along the main veins. Carpinus caroliniana Carpinus betulus Betulaceae Carpinus caroliniana – American hornbeam Buds – Lateral buds of American hornbeam are shorter and straight. The hairs are tufted in the bud scales rather than being straight and loose in European hornbeam. European hornbeam buds also tend to curve toward the stems. Carpinus caroliniana Carpinus betulus Betulaceae Carpinus caroliniana – American hornbeam Trunk – The trunk on American hornbeam is attractive, but does not take on the exaggerated fluted, muscle-like appearance of European hornbeam. Betulaceae Carpinus caroliniana – American hornbeam Culture: Full sun or partial shade. American hornbeam does well in most garden soils, but prefers a deep, organic slightly acidic soil. Best handled as a containergrown plant. Hardy in zones 9 to 3. Betulaceae Carpinus caroliniana – American hornbeam Culture: American hornbeam can be pruned in a similar fashion to European hornbeam. Betulaceae Corylus avellana ‘Contorta’ – Harry Lauder’s Walking stick Harry Lauder’s walking stick is a selection of European filbert with twisted contorted stems and leaves. It is useful as a large specimen shrub for winter interest. The genus name comes from the Latin for helmet (korys) referring to the elongated sepal tissue that covers the fruit. Betulaceae Corylus avellana ‘Contorta’ – Harry Lauder’s Walking stick Growth habit – A slowgrowing plant with an upright, rounded habit. Twisted branches makes an interesting winter specimen. Betulaceae Corylus avellana ‘Contorta’ – Harry Lauder’s Walking stick Plant height - Can reach 15 feet in height and 10 feet wide. Betulaceae Corylus avellana ‘Contorta’ – Harry Lauder’s Walking stick Flowers – Male and female flowers are produced separately on the same plant in February. Male flowers are pendulous catkins. Female flowers have red styles protruding from the bud. Female flowers Male flowers Betulaceae Corylus avellana ‘Contorta’ – Harry Lauder’s Walking stick Fruit – Fruits are rarely produced on Harry Lauder’s Walking stick because they are self-sterile and require a pollinator. The true species of European filbert (C. avellana) is produced commercially for its edible hazel nuts. Commercial hazel nuts A rare fruit produced on Corylus avellana ‘Contorta’ Betulaceae Corylus avellana ‘Contorta’ – Harry Lauder’s Walking stick Leaf – Alternate, simple leaves are broadly ovate with a double serrate margin. The leaves and stems are more twisted on the cultivar than the species. Betulaceae Corylus avellana ‘Contorta’ – Harry Lauder’s Walking stick Buds – Male buds visible during the winter as elongated terminal groups and can provide additional winter interest, especially after an ice storm. Male flower buds Betulaceae Corylus avellana ‘Contorta’ – Harry Lauder’s Walking stick Culture: Full sun or light shade. An easy plant to grow. Tolerant to most landscape soils. Hardy in zones 8 to 4. Betulaceae Corylus avellana ‘Contorta’ – Harry Lauder’s Walking stick Culture: Very attractive to Japanese beetles that can cause severe feeding damage to the leaves. Betulaceae Corylus avellana ‘Contorta’ – Harry Lauder’s Walking stick Culture: Grafted plants can sucker and make unsightly plants because the rootstock produces nontwisted stems that quickly over grow the slower growing cultivar. The nursery row to the right is a layering bed where plants will be produced on their own roots. Plants produced by layering do not have the suckering problem. Betulaceae Corylus avellana ‘Contorta’ – Harry Lauder’s Walking stick Cultivars: ‘Red Majestic’ is a purple foliage version of Harry Lauder’s walking stick. Purple leaf color does not hold into the heat of the summer. The plant pictured here was obviously propagated from grafting, because the greenleaved rootstock (red arrow) is sucking from the base of the plant and will need to be pruned away. Betulaceae Corylus avellana – European filbert Cultivars: ‘Pendula’ produces a flat-topped plant with drooping branches. It is usually grafted on a standard and is slow-growing. Betulaceae Birch family dichotomous key Vegetative buds on short stalks. Leaves with an indent or notch at the tip (emarginate) – Alnus glutinosa. Leaves with rounded or acuminate (pointed) tip – Alnus cordata. Vegetative buds not on short stalks (sessile). Bark on young trees smooth or exfoliating; fruit a winged nutlet. Bark white; twigs with prominent lenticles. Leaves with a long petiole (>1 in.); leaf tip long and tapering – Betula populifolia. Leaves with short petiole (<1 in.); leaf tips short acuminate. Leaf lower surface pubescent at veins – Betula papyrifera. Leaf lower surface glabrous (no hairs); branchlets hanging – Betula pendula. Bark on young trees usually reddish-brown, orange-brown; twigs without lenticels. Bark on young stems with a wintergreen scent when scraped – Betula lenta. Bark without wintergreen scent – Betula nigra. Bark does not exfoliate; fruit if present is a nut or nutlet enclosed in a leafy bract. Stems twisted; leaves ovate, as long as wide – Corylus avellana ‘Contorta’. Stems not twisted; leaves oblong, longer than wide. Fruit a nutlet enclosed in an inflated “hop-like” bag – Ostrya virginiana. Fruit a nutlet contained within leafy bracts. Buds with few straight hairs and bud > 4 mm (0.16 in.) – Carpinus betulus. Buds with tufted hairs and bud < 4 mm (0.16 in.) – Carpinus caroliniana.
