All of the species or cultivars described have been chosen for their relative disease- and insect-free qualities and their desirable horticultural attributes. The list was reviewed by a plant pathologist, an entomologist, and a horticulturist and includes information on some of the pertinent cultural characteristics of each species to help you decide whether the shrub is the right choice for the landscape you have in mind. Plants marked with an asterisk (*) are native to Virginia and recommended by the Virginia Native Plant Society.
A short list of shrub species that tend to have chronic problems and should, with some exceptions, be avoided is also included in this fact sheet. Although species listed as “problem shrubs” tend to have chronic problems in the landscape, disease- and insect-resistant cultivars of some of these species may be available. Consult your local nursery personnel or Extension agent for recommendations on the latest cultivars.
Berberis x gladwynensis ‘William Penn’ (William Penn barberry) is a medium, evergreen shrub that is armed with spines. This densely growing barberry has somewhat showy (upon close inspection) yellow flowers in spring and is relatively drought-tolerant. William Penn barberry is typically used as a low hedge or in border plantings. Some winter damage can occur in Zone 6a.Cepalanthus occidentalis* (buttonbush) is a large shrub that produces white flowers in globular heads in June, July, and August. Buttonbush is somewhat lanky, but is a good choice for informal landscapes. It does best in moist soil and does not tolerate drought
Clethra alnifolia* (sweet pepperbush) is tolerant of wet soils. It tends to form colonies slowly, and the cultivar ‘Sixteen Candles’ remains compact. Its very fragrant white flowers open in July. Pictured here is the pink-flowered cultivar ‘Rosea’.
Cornus alba (Tatarian dogwood) has beautiful, red stems. Although several diseases are reported to occur on this species, experience shows that disease problems are rare on C. alba in Virginia landscapes. Japanese beetles can be a problem and borers sometimes follow mechanical injury to the plants. C. alba is quite vigorous and can sometimes overgrow neighboring shrubs. Variegated cultivars, such as the one pictured here, are available.
Cornus mas (Corneliancherry dogwood) is a large, multi-stemmed shrub or small tree. It has attractive, flaky bark and small but showy, yellow flowers in early spring. Several cultivars, including variegated ones, are available.
Forsythia x intermedia (border forsythia) is a common, large, fast-growing shrub that suffers few disease and insect problems, but needs frequent grooming. Phomopsis gall, a fungal disease associated with dieback, is occasionally a problem on forsythia stems. Border forsythia is adaptable to a wide range of soils. Full sun is best for flowering.
Fothergilla major (large fothergilla) is a rounded, multi-stemmed shrub that has exceptional fall color and essentially no disease problems. It must be planted in acid soil and does not do well in dry soil. (no photograph)
Hydrangea arborescens* (smooth hydrangea) is a low-growing, native shrub that produces pretty white flowers in July. It prefers partial shade, but can be grown in full sun with supplemental water. It can be cut back every year because it flowers on new wood. Pictured here is the cultivar ‘Annabelle’.
Ilex verticillata* (winterberry) does well in both heavy and light soils, but is native to swampy areas and prefers moist, acid soils high in organic matter. It produces persistent red berries that are a nice accent to the winter landscape. At least one male plant must be planted among female plants for fruit production. The cultivar ‘Winter Red’ is a prolific fruit-producer. Compact, dwarf cultivars, such as ‘Red Sprite,’ are also available.
Ilex vomitoria*1 (Yaupon holly) is adapted to both dry and wet soils. Like other hollies, it is susceptible to scales and sooty mold. I. vomitoria is suitable for Zones 7-9. There are several cultivars, which vary in size and form. Pictured here is the dwarf cultivar ‘Nana’.
Juniperus chinensis (Chinese juniper) is a large shrub or a tree. Like all junipers, it needs full sun. Many cultivars are susceptible to the fungal diseases, Phomopsis blight and Kabatina tip blight, but some cultivars, such as ‘Keteleeri,’ ‘Pfitzeriana’ (pictured left), ‘Pfitzeriana Aurea’ (middle photo), var. sargentii, and var. sargentii ‘Glauca’ have resistance to these diseases. The upright cultivar pictured on the right is ‘Torulosa.’
Juniperus conferta (shore juniper) has lush, soft foliage when grown in the right soil. The main problem seen on this species is stress from being planted in poorly drained soils. Shore juniper can tolerate dry, sandy soils, but does poorly in heavy, clay soils. The prevalent cultivar in the trade is ‘Blue Pacific,’ pictured here.
In contrast to the shrubs described above, those listed below can be considered problem shrubs. These species or cultivars are often sent to the Plant Disease Clinic at Virginia Tech for diagnosis. Avoid using these shrubs in new landscapes if any of the species listed as “problem-free” can be used instead.
Buxus sempervirens ‘Suffruticosa’ (English boxwood) tends to suffer from root diseases, including Phythophthora root rot, English boxwood decline, and nematode feeding. Minimizing cultural and environmental stresses can help prevent these diseases, but control options are limited once symptoms develop. The species B. sempervirens (common box) is not prone to English boxwood decline and tends to have fewer root problems than Buxus sempervirens ‘Suffruticosa’. B. microphylla (littleleaf box) is also relatively problem-free. Hybrids of B. sempervirens and B. microphylla var. koreana are also available.
Ilex crenata (Japanese holly) often suffers from black root rot, a fungal disease, in the landscape. Typical symptoms include sectional dieback of the foliage and blackened roots. Control involves repeated fungicide treatments, which can keep the disease in check but do not rid the soil or roots of the fungus. Certain other hollies, including Ilex glabra (inkberry), Ilex x meserve(blue or Meserve holly) and Ilex opaca (American holly), are also susceptible to this disease, although no species is as chronically affected by it as Japanese holly.
Photinia x fraseri (redtip) is susceptible to the fungal disease Entomosporium leaf spot. Symptoms of this disease can be quite severe on plants that are sheared and/or fertilized frequently in the summer. These practices stimulate succulent growth, which is very susceptible to infection.
Dirr, M.A. 1998. Manual of Woody Landscape Plants, 5th ed. Stipes Publishing L.L.C., Champaign, Ill. 1187 pp.
Flint, H.L. 1983. Landscape Plants for Eastern North America. John Wiley & Sons, Inc., Hoboken, N.J. 677 pp.
Johnson, W.T., and Lyon, H.H. 1991. Insects that Feed on Trees and Shrubs, 2nd edition. Cornell University Press, Ithaca, N.Y., and London, UK. 560 pp.
Sinclair, W.A., and Lyon, H.H. 2005. Diseases of Trees and Shrubs, 2nd edition. Cornell University Press, Ithaca, N.Y., and London, UK. 660 pp.
Whitcomb, C.E. 1996. Know It & Grow It. Lacebark, Inc., P.O. Box 2383, Stillwater, Okla.
Virginia Cooperative Extension materials are available for public use, re-print, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.
Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Alan L. Grant, Dean, College of Agriculture and Life Sciences; Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; Jewel E. Hairston, Administrator, 1890 Extension Program, Virginia State, Petersburg.
May 1, 2009