Evergreen Rhododendron (Rhododendron species)
Height: 6 to 15 feet (depending on species or cultivar) Spread: 5 to 15 feet (depending on species or cultivar) Shape: Upright, rounded to oval
There are many Rhododendron species and cultivars thereof, as well as hundreds of hybrids. Rhododendron species come in many sizes and shapes with a wide variety of leaf and flower forms. Azaleas are in the Rhododendron genus and will discussed in another article.
Zone: 4 to 7 (depending on species or cultivar) Light: Partial shade
Moisture: Moist to average
Soil Type: Sandy, loam, or clay loam pH Range: 3.7 to 6.5
Suggested uses for this plant include border, massing, foundation and specimen plant.
Rhododendron plants do best with afternoon shade. Thus, they are best placed on the east side of a house (within shade pattern). The soil must be well drained, thus a heavy clay soil is inappropriate for Rhododendron.
Mulch plants and irrigate during periods of drought. Prune all diseased branches as soon as noticed.
Susceptible to a number of diseases including root rot, petal blight, and dieback.
Insect pests include aphids, borers, lacebugs, scale insects, and red spider mites, weevils and whitefly.
Consult garden centers, historic or public gardens and arboreta regarding cultivars and related species that grow well in your area. The American Rhododendron Society (http://www.rhododendron.org/) covers many issues and types of evergreen rhododendrons. Catawba rhododendron (Rhododendron catawbiense) cultivars:
`Roseum Elegans' has lavender pink flowers.
`Nova Zembla' has red flowers and is cold and heat tolerant.
If catawba rhododendron is in a suitable place it can grow to 15 feet tall and almost as wide. Thus, careful placement is needed.
Yak rhododendron (Rhododendron yakushimanum) is a slow-growing species and is more suitable for areas with limited space around a house. There are several cultivars of this species. There are hundreds of Rhododendron hybrids in the nursery trade with a vast array of sizes, forms, hardiness, leaf, and flower characteristics.
When selecting a Rhododendron species, the most important characteristics to check area the species’ hardiness and tolerance of sun and heat. Once you have determined that the species is appropriate for your area, then select a cultivar with the appropriate size and desired flower/leaf characteristics.
This material was developed by Carol Ness as part of the Interactive Design and Development Project funded by the Kellogg Foundation.
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October 17, 2018