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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

Broad-leaved Evergreen Shrubs for Iowa

This article was published originally on 6/11/2004

Lilacs, dogwoods, and spireas are common deciduous shrubs in the home landscape. Junipers and yews are widely planted narrow-leaved evergreens. Though less popular, broad-leaved evergreen shrubs are another group of attractive shrubs for the home landscape. In addition to their evergreen foliage, many broad-leaved evergreens possess attractive flowers or fruit.

Broad-leaved evergreens are often more demanding that other shrubs. Many require sheltered sites and well-drained, acid soils. Careful site selection and proper soil preparation often are necessary to ensure the success of broad-leaved evergreens.

The following paragraphs provide a brief descriptions of several broad-leaved evergreen shrubs that can be grown in Iowa.

Korean Boxwood

Korean boxwoods (Buxus microphylla var. koreana) can be used as specimen plants or formal hedges. 'Wintergreen' and 'Winter Gem' have small, rounded, light green leaves. 'Green Mound,' 'Green Mountain,' and 'Green Velvet' are three recently introduced hybrids that possess dark green foliage and grow about 3 feet tall.

Boxwoods perform best in moist, well-drained, neutral to slightly alkaline soils. They also require a sheltered location. Boxwood foliage is susceptible to winter burn when subjected to strong winds or intense sun during the winter months. A location on the east side of a building is often a good site.

Wintercreeper

Wintercreeper (Euonymus fortunei) is commonly used as a groundcover or vine. However, several varieties also can be used as low-growing shrubs or hedges. 'Canadale Gold' and 'Emerald 'n Gold' have glossy green leaves with golden yellow margins. 'Emerald Gaiety' has green foliage with irregular white margins. All three varieties grow 2 to 3 feet tall. 'Sarcoxie' is an upright form with dark green foliage. It can reach a height of 4 to 5 feet.

Wintercreeper can be grown in full sun to shade. While it adapts to most soils, wet poorly drained sites should be avoided. Euonymus scale is a common insect pest. Severe scale infestations can destroy plants.

Inkberry

Inkberry (Ilex glabra) is a holly with dark green foliage. Inkberry and other hollies are dioecious. Dioecious plant species produce male and female flowers on separate plants. Only the female plants produce fruit. However, a male plant is required for pollination and fruit set. Female plants produce black, pea-size fruit. Plants grow 6 to 8 feet tall. While inkberry is evergreen, it often times loses its leaves in winter during extreme cold. It is best used in protected areas as an accent or specimen plant in the home landscape. 'Compacta' is a dwarf female variety that grows 3 to 4 feet tall. 'Shamrock' (female) grows 3 feet tall. 'Nordic' (male) is a compact, rounded shrub that grows 3 to 4 feet tall. Inkberry requires a moist, acid soil in partial shade to full sun.

Meserve Hybrid Holly

Several hybrid hollies, collectively known as Meserve hybrid hollies (Ilex x meserveae), also can be grown in Iowa. 'Blue Prince,' 'Blue Princess,' 'Blue Boy,' and 'Blue Girl' have dark, bluish green foliage and often are referred to as blue hollies. The female varieties have attractive red fruit. Other attractive Meserve hybrids include China Boy and China Girl . Meserve hollies are variable in height. Most varieties grow 5 to 10 feet tall. They are hardy in USDA Hardiness Zone 5.

Meserve hollies perform best in moist, well-drained, slightly acidic soils. Since they are susceptible to desiccation injury from bright sun and dry winds in winter, Meserve hollies should be planted in protected sites, such as on the east sides of buildings.

Oregon Grapeholly

Oregon grapeholly (Mahonia aquifolium) has compound leaves with holly-like leaflets. The foliage is shiny and dark green in summer. In winter, the leaves take on a bronze-purple color. Plants produce bright yellow flowers on upright, 2 to 3 inch long spikes (racemes) in spring. Bluish black, grape-like fruit develop in late summer. Oregon grapeholly grows 3 to 4 feet tall. It is hardy in USDA Hardiness Zone 5.

Plants perform best in moist, well-drained, acid soils. Oregon grapeholly requires a sheltered, shady location. Exposure to winter winds or sun can damage the foliage.

Catawba Rhododendron

Several varieties of Rhododendron catawbiense can be grown successfully in Iowa. Catawba rhododendrons have large, dark green leaves and 5 to 6 inch diameter flower clusters. 'Album' (white flowers), 'English Roseum' (light rose), 'Nova Zembla' (red), and 'Roseum Elegans' (lavender-pink) are hardy to -25 F.

All rhododendrons require well-drained, acid soils with a pH of 4.5 to 5.5. Rhododendrons are susceptible to winter burn when planted in windy, exposed sites. Sheltered areas that receive morning sun and afternoon shade are often good planting sites for rhododendrons. Catawba rhododendrons perform best in southeast Iowa.

Marjatta Hybrid Rhododendron

Developed at the University of Helsinki in Finland, the Marjatta hybrid rhododendrons (Rhododendron x marjatta) have broad evergreen leaves and large showy flowers. Their flower buds are hardy to -30 to -35 F. 'Haaga' has an upright growth habit and will grow up to 6 feet in height. It has dark green foliage and rosy pink flowers. 'Elviira' is a low growing, spreading plant with a mature height of 2 feet. Its flowers are bright red. Possessing a dense spreading habit, 'Hellikki' ultimately reaches a height of 5 to 6 feet. Flowers are dark violet-red. 'Mikkeli' grows 5 to 6 feet tall and produces white flowers with green flecks in the upper portion of the corolla. The flowers of 'Peter Tigerstedt' are white with violet flecks in the upper part of the corolla. An upright grower, 'Peter Tigerstedt' may grow to a height of 6 feet. The Marjatta hybrid rhododendrons perform best in sites protected from winter sun and wind.

Peter J. Mezitt Hybrid Rhododendron

The 'PJM' rhododendron grows well over much of the upper Midwest. The small, evergreen foliage is dark green in summer, but turns to a maroon-purple in the fall. The flower buds (hardy to -35 F) produce bright lavender pink blossoms in mid to late April. The mature height and spread of the 'PJM' rhododendron is approximately 4 to 6 feet tall. Several selections of 'PJM' are available and include 'Black Satin' (winter foliage is shiny, coal black), 'PJM Elite' (blossoms are slightly more pink), and 'PJM Compact' (4 feet tall, lavender pink flowers). 'PJM' was introduced by the Weston Nursery in Hopkinton, Massachusetts and was named after its owner Peter J. Mezitt.

Two other Weston Nursery hybrids, 'Aglo' and 'Olga Mezitt,' also do well in Iowa. 'Aglo' has light pink flowers with dark pink throats. It blooms about 7 to 10 days after 'PJM.' The small green leaves turn to a bronze color in fall. 'Olga Mezitt' produces bright pink flowers on 4 to 5 foot shrubs.

When selecting shrubs for the home landscape, consider some of the broad-leaved evergreens. Though they may require more care than other types, broad-leaved evergreens are attractive additions to the home landscape.



This article originally appeared in the 6/11/2004 issue.

Year of Publication: 
2004
Issue: 
IC-491(13) -- June 11, 2004