Christopher J. Starbuck and Ray R. Rothenberger
Department of Horticulture, University of Missouri-Columbia, Agricultural publication G06820 Reviewed February 15, 1997
The most highly prized landscape plants are broad-leaved evergreens. They are the true aristocrats of our gardens. However, many of them require special attention if they are to develop into attractive long-lived plants.
Wide fluctuations in temperature, prolonged dry periods, drying winds and bright sunshine of the Midwest are not ideal conditions for most broad-leaved evergreens. Special soil preparation and a carefully selected location are usually necessary to ensure the success of these plants. However, the year-round beauty and special effect they give to the landscape makes them well worth the effort.
The broad-leaved evergreens are valued chiefly for their evergreen foliage, but many of them possess other desirable ornamental traits. They are generally clean plants, dropping few leaves at any one time, and they never become overgrown and weedy as some other ornamentals do. In addition, most of them are relatively free from insect and disease problems.
Broad-leaved evergreens prefer a rich, well-drained, slightly acid soil. Increasing organic matter content and improving drainage can improve an existing poor soil. For more information on soil improvement, see MU publication G06955 Improving Lawn and Landscape Soils.
Locate broad-leaved evergreens subject to winter injury so they receive protection from the wind and afternoon sun, especially in winter. North and east sides of buildings are ideal. Wind and sun protection from fences or large plants also helps prevent injury.
Broad-leaved evergreens should be fertilized only in the spring. Summer or fall fertilization may induce late season growth that is highly susceptible to winter injury. Winter scorch of foliage can also develop if plants dry out over winter. To prevent this, water plants in late summer and fall if rainfall has been deficient.
Size of plant is also important to winter hardiness of some species. A small, young plant may be easily killed while the same species is quite hardy when larger plants are used.
Poor culture, attacks by insects or disease or any other factor that weakens a plant makes it more subject to winter injury.
Many plants described in the following section are not hardy in all parts of the state. The zones where a plant can be most reliably grown are listed with each plant. These plant-hardiness zones correspond to the ones shown on the map (Figure 1). They are based on the average annual minimum winter temperature taken from long-term weather records. Soil type, rainfall and summer temperature also affect winter hardiness. Therefore, these zones are only a rough estimate of a plant's ability to grow in a particular area.
When broad-leaved evergreens are planted and located properly, they can add year-round interest to the landscape and provide a pleasant contrast to needle-leaved evergreens in both winter and summer.
Glossy abelia may grow to a height of 5 feet in southern areas, but it is smaller when grown in colder climates. It is valued for its small pink flowers that appear from June to frost. Abelia may be used as a specimen plant or as a small hedge. The glossy foliage appears in late spring.
In winter foliage turns purple, and the plant may lose some foliage if winter is severe. Pruning of dead twigs is often necessary in late spring after growth starts. In severe winters tops may be killed back, but new shoots develop rapidly from the base.
The plants commonly called azaleas and those called rhododendron belong to the botanical genus Rhododendron. It is the largest group of woody ornamental plants in the world. More than 2,000 species, varieties and hybrids have been recognized. There is no clear-cut distinction between the group known as Azaleas and one called Rhododendron.
Special soil conditions and cultural requirements are needed to grow azaleas and rhododendrons. Because of this and the many species and varieties available, they cannot be covered adequately here. For details of their culture and selection, see MU publication G06825, Growing Azaleas and Rhododendrons.
Wintergreen barberry, an excellent small shrub, is attractive in the garden throughout the year. The evergreen foliage is 3 inches long, narrow and spiny. The thorny twigs make it an excellent barrier and hedge plant. Small yellow flowers appear in May. Bluish-black berries add interest in the fall. Wintergreen barberry is very hardy and easily grown.
Boxwood has been a popular broad-leaved evergreen, particularly in the eastern and southern U.S., where very old specimens can be found. Boxwoods make excellent specimen plants or hedges. They can be easily pruned to any desired shape. Of the available boxwood types, the Korean box is most hardy and easily grown. The leaves, however, tend to lose their color in winter. In shady locations the winter discoloring is less severe. The common boxwood is suitable only for southeastern Missouri.
This slow-growing plant with spreading, arching branches and dark lustrous leaves produces fragrant, bell-shaped flowers in early spring. It needs shade for best growth and therefore is most suitable beneath large evergreens. It is related to Japanese Andromeda and requires the same growing conditions.
Most varieties of wintercreeper euonymus are vines or groundcovers. Sarcoxies euonymus, developed at Sarcoxie, Missouri, is an erect form that makes an excellent broad-leaved evergreen shrub. It grows well in full sun or shade, but retains its green winter color better in shade.
Euonymus scale, a white covered scale insect, may attack the stem and leaves of euonymus. A severe infestation will make the underside of leaves and the entire stem white and will eventually kill the plant unless controlled.
Spreading euonymus is also known as Euonymus patens. It is evergreen in the south, but in colder areas leaves may turn brown in late winter and hang onto the plant until new leaves are produced in the spring. It grows well in full sun, but the leaves remain green longer if it gets winter shade. The fruit capsules open in the fall to reveal the bright reddish seed.
Spreading euonymus may be attacked by euonymus scale but not as readily as wintercreeper. The two varieties of spreading euonymus most commonly grown are 'Manhattan,' a variety that retains good green winter color, and 'Pauli,' which is reported to retain even better green winter color.
The spiny, evergreen leaves and bright, red berries of American holly are familiar to most people. American holly is native in southeastern Missouri. It is slow growing and in other area of the state should be used as a large shrub, although it will eventually develop into a small tree.
The sexes of holly are on separate plants. Some plants produce only male flowers and others produce only female flowers. Only the female plants produce berries, but both sexes must be present to ensure fruiting. One male plant is enough to pollinate the flowers of six to eight female plants.
Acid soils high in organic matter and with good drainage are essential for growing hollies.
Most Japanese hollies produce small, spineless leaves and black fruit. They are popular, small, compact evergreen shrubs. Some of the most commonly grown of the many available varieties include:
The Chinese Holly produces large, spiny, glossy green leaves and bright red berries. It is one of the few hollies that does not require pollination to produce berries. Therefore, there is no reason to plant the male forms. Chinese holly is very popular where it can be grown, but is reliably hardy only in the warmer areas of Missouri. The most commonly grown varieties of Chinese holly include:
The inkberry, a native black-fruited holly, is not as attractive an ornamental as the other hollies, but it is one of the most hardy of the group. Leaf size, shape and glossiness vary considerably. The selection 'Compacta' should be used in the landscape. Occasional pruning will keep the plant from developing loose, open growth.
Narrow evergreen leaves and a dense branching habit makes this an excellent specimen or accent plant when sheared. It may be used unsheared in screen plantings but becomes more loose and open. It is heavily berried and does not need a male plant nearby to produce fruit.
This attractive, broad-leaf evergreen may reach 5 feet but is usually smaller in our climate. The new foliage is bronze colored in spring, soon turning a lustrous medium green. The flowers, borne in late March, are a creamy white in long, drooping clusters. This broad-leaved evergreen needs protection from winter sun and wind to prevent leaf scorch and killing of the flower buds. A light, well-drained acid soil high in organic matter will produce the best plants.
Leatherleaf viburnum is a coarse-textured shrub that may eventually grow 6 feet tall. Its large, wrinkled leaves persist well during cold weather. In late winter leaves turn yellowish and drop off as new foliage emerges in spring. The leaves are up to 6 inches long. The flat clusters of white flowers are not as showy as the red to black berries that follow.
Leatherleaf Viburnum prefers a well-drained soil with protection from afternoon sun, especially in winter. This shrub is often used in corner plantings or for accent in the shrub border. It is suitable for planting beneath pines or other large evergreen trees.
The large, lustrous evergreen foliage of the Southern Magnolia makes it a very desirable ornamental. It develops into a large tree in southeastern Missouri, but in the St. Louis area, about its northern limit, it rarely gets over 20 feet tall. Its large, white flowers are produced abundantly in southern areas but only occasionally in colder climates.
Southern magnolia needs to be planted in a well-protected spot to survive without injury in any but the warmest parts of the state. Wind protection is essential as the large leaves are easily damaged by winter winds.
The reedlike stems with the evergreen leaves clustered at the tip gives this plant an exotic bamboo-like appearance. It is best known for its clusters of bright red fruit in the fall. It is a highly ornamental plant, but unfortunately it will only develop properly and fruit in the warmest parts of the state. In colder areas plants are often killed back to ground level but usually sprout from the roots in spring.
Oregon Holly-Grape is a fairly coarse, stiff shrub that may reach 6 feet. In April the plant is covered with bright yellow flowers. In the summer, the bluish-black grapelike fruits develop. The foliage is dark, lustrous and holly-like. In winter, the leaves turn a bronze-purple color. This shrub is usually semi-evergreen and much of the foliage does not persist throughout the winter. Protection from winter sun and wind will help it remain more attractive during the winter.
The large, leathery evergreen leaves held stiffly horizontal on the shrub make it a striking specimen. When grown in partial shade the leaves do not change color markedly in the fall. It is not as hardy as the Oregon holly-grape and needs a well-protected, shady spot to survive.
Pyracantha is a semi-evergreen shrub. It produces showy, small white flowers in the spring, but the clusters of bright orange berries it produces in the fall that hang on the plant until mid-winter are its main attraction. Pyracantha can be grown as an individual specimen plant, as a hedge or barrier or trained flat against a wall to look like a vine. It normally grows to 6 or 7 feet tall and can spread to almost twice as wide, so ample space must be given for the plant to develop. A dwarf variety is available for smaller areas.
Pyracantha is one of the few plants that seems to do best on poor soil. Good soil and high fertility produces rampant growth susceptible to disease and low in berry production.
Yucca is a rugged plant able to take almost any situation. The plant is normally around 2 feet high with all the leaves arising from a central point at ground level in a rosette fashion. The leaves are long, pointed and rigid. In summer the plant produces a flower stalk about 4 feet high with a large head of pendulous, creamy-white flowers.
Yucca is used as an accent plant and is frequently used in modern ground plantings. The plant is suited best to hot, dry situations.
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