How to Grow Rhododendrons in South Carolina

Quick Guide to Rhododendrons (At a Glance)

This Quick Guide provides the essential growing requirements for rhododendrons in South Carolina.

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  Rhododendron catawbiense ‘Roseum Elegans’ flowers.
  Joey Williamson, ©2011 HGIC, Clemson Extension

  Plant Type: Southern native evergreen rhododendrons and hybrids

• Height & Spread: 5 to 6 feet for Carolina types; up to 20+ feet for rosebay; forms range from compact to loose
• Light Requirements: Dappled shade; filtered light under tall pines/oaks; avoid hot afternoon sun
• Best Planting Time: Fall (roots begin establishing before early spring growth)
• Soil Type: Well-drained, high in organic matter; pH 4.5 to 6.0
• Watering Needs: Shallow-rooted; requires consistent moisture during establishment and dry periods
• Mulch: 2 to 3 inches of pine bark, pine straw, or compost; keep mulch away from the main stem
• Fertilizer: Minimal; only after establishment and when a specific need is identified
• Maintenance Level: Low once established; limited pruning; deadheading recommended
• Common Problems: Root rot, blight, dieback, lace bug, mites, scale, borers
• Landscape Uses: Woodland gardens, foundations, hedges, specimens, city gardens
• Companion Trees: Oaks and pines (provide filtered shade, mulch, nutrients)

How to Grow Rhododendrons in South Carolina

This section outlines the essential care requirements for rhododendrons in South Carolina gardens.

Rhododendrons are not difficult to grow in South Carolina, where the soil and environment are suitable for their culture.

Cultural requirements for rhododendrons and azaleas are basically the same, but their structures are different. Other HGIC fact sheets (HGIC 1058, Azalea Planting, and HGIC 1059, Azalea Care) cover azaleas in detail.

This publication will focus on the Southern native evergreen rhododendrons and hybrids.

Rhododendron Ornamental Features

Rhododendron flower characteristics and foliage traits vary widely among species and hybrids.

Spectacular rhododendron blossoms will appear anywhere from early spring to midsummer, with a color range much greater than that of roses.

Rhododendron Color Range:

• Pure white
• Cream and yellow
• Apricot and salmon
• Soft pinks
• Deep reds
• Lavender
• Deep purple and blue

Some have large trusses (“collection” of flowers) 12 inches across, while others have blossoms that hang as individual bells.

There is a wide variation in leaf shape and color.

Rhododendron Mature Height and Spread

Understanding rhododendron growth habits helps with choosing the right variety for your landscape.

Rhododendrons come in many shapes and sizes, from the low-growing Carolina (5 to 6 feet tall) to the large native rosebay (20 feet and more). Some varieties are rounded and compact, while others have a loose growth habit.

Rhododendron Landscape Uses in South Carolina

Rhododendrons offer versatile landscape uses across South Carolina’s residential and natural environments.

Rhododendrons can be used in an open woodland setting under tall pines or oaks, in a small city garden, as a foundation planting for a suburban home, or to landscape a large city building. They can be used as specimen plants, foundation plantings, and hedges.

Oaks and pines are the most commonly mentioned companions for this beautiful shrub. They provide a high canopy of filtered shade while still providing the high degree of light intensity necessary for growth. The mulch provided by oak and pine trees breaks down, providing essential nutrients.

Keep the soil aerated and moist. For plants that do not naturally have these conditions, additional support may be necessary.

How to Cultivate Rhododendrons in South Carolina

Successful rhododendron cultivation depends on proper site selection, drainage, soil preparation, planting methods, mulching, watering, and fertilizing. Proper rhododendron care in South Carolina depends on matching the plant to the right site and soil conditions.

Rhododendrons have a few requirements: excellent drainage, a soil pH between 4.5 and 6.0, and protection from hot afternoon sun.

Best Site Selection for Rhododendrons

Choosing the right planting location is one of the most important steps in rhododendron care.

Plant the rhododendron out of the wind and in dappled shade, preferably from a high cover of limbs that will give filtered shade all day. Some varieties will take a few hours of direct sun in the morning, but most need protection from the intense Southern sun. Trees should be tall enough to be limbed up so the shrubs will get plenty of light. These trees will cut the force of drying winds in both winter and summer.

Best Drainage Conditions for Rhododendrons

Drainage is improved by planting on a slope – a northern slope is preferable to a southern slope. When using rhododendron in a foundation planting, avoid southern exposures. The best place to plant is on the north or east side of a building.

Soil Requirements for Growing Rhododendrons

Soil preparation plays a major role in long-term rhododendron health.

The soil for these woodland plants must be well-drained and high in organic matter. Organic matter improves drainage in clay soils and will increase a sandy soil’s ability to retain water and nutrients.

Add about 4 inches of pine bark over an area two to three times the area to be covered by the branches of the plant you are setting. Mix it into the top 6 to 8 inches of soil using a tiller or shovel.

Rhododendron Planting Tips

The best time to plant is in the fall when the roots have a period to acclimate and prepare for early spring growth. The plant will require a good bit of water during the first year of establishment. Refer to HGIC 1058, Azalea Planting, for planting instructions.

How to Mulch Rhododendrons Correctly

Mulch helps to retain soil moisture around the roots. As it breaks down, mulch provides nutrients for the shrubs and improves the soil texture. Furthermore, it aids in weed control, eliminating the need to disturb the roots through weeding.

A 2- to 3-inch layer of compost, pine bark, or pine straw is excellent mulch. Extend the mulch well beyond the outermost branches of the plant. Pull mulch away from the main stem to help prevent disease.

Rhododendron Watering Guidelines

Consistent soil moisture is a key requirement for rhododendron care, especially during establishment.

Rhododendrons are shallow-rooted plants and require irrigation during dry periods. This is especially true of those planted in the preceding spring.

Rhododendrons planted in warm weather in sandy soils may require watering of the root system twice a week during the first year. Newly planted rhododendrons require regular watering during dry spells for the first several years.

Pull back a small area of mulch beneath the canopy of the plant and check the soil moisture level. When the soil feels dry, water it to a depth of 8 to 12 inches. Use soaker hoses or drip irrigation to slowly water the base of the plant.

Be aware that rhododendrons in waterlogged soils are prone to decline and become susceptible to root rot diseases. It is essential to reach a balance between regular, deep watering and good drainage to promote a healthy plant.

How to Fertilize Rhododendrons

Rhododendron nutrient needs are relatively low compared to many other landscape shrubs.

With proper soil preparation and mulching, very little fertilizer is necessary – particularly for older, established plants. Do not fertilize rhododendrons at the time of planting; newly planted shrubs can be fertilized after they have become established.

Allow newly planted shrubs one to several months, depending on their size, to begin establishing their root system in the landscape soil before applying fertilizer. Once the shrubs are established, have a specific reason, such as increasing the growth rate or correcting a nutrient deficiency, before deciding to fertilize. Maintaining a mulch layer of compost or other organic material over the roots of shrubs typically provides sufficient nutrients for adequate growth and plant health.

Signs of Nutrient Deficiency

Several symptoms, including stunted growth, smaller-than-normal leaves, a light green to yellowish leaf color, and early leaf drop, can indicate a nutrient deficiency. Be aware that these same symptoms can be caused by other problems, such as heavily compacted soil, stress from insects, disease organisms, and weeds, as well as excessively wet or dry soil conditions. Fertilization will not correct those problems, so be certain to identify the cause of the symptoms and treat them accordingly.

Having your soil tested is one way to determine if applying fertilizer will benefit your shrubs. Soil testing information is available in HGIC 1652, Soil Testing. In the absence of a soil test and other cultural or pest problems, use a complete fertilizer with a ratio of 3:1:2 or 3:1:3, such as 12-4-8 or 15-5-15.

When to Apply Fertilizer

The best time to apply fertilizer is when it will be readily absorbed by the roots of the plant and when the soil is moist, which can be any time from late spring (after new growth emerges) up to early fall. Fertilize after flowering, especially when using a slow-release fertilizer. Avoid fertilizing plants stressed by drought during the summer months. Without water, plants are unable to absorb nutrients, so it is best not to fertilize if water is unavailable.

Since low acidity is of particular importance for rhododendrons, test the soil periodically through your local Clemson Extension office to determine the pH level as well as fertility levels. For more information on fertilizing rhododendrons, refer to HGIC 1059, Azalea Care.

How to Prune Rhododendrons

Rhododendrons require minimal pruning; however, proper timing is essential for healthy growth and flowering.

Remove dead or damaged wood at any time. Pruning to shape the plant or to keep it within bounds should be done after the plant has flowered.

How to Deadhead Rhododendrons (Important for Flowering)

Deadheading is an important type of pruning. It involves snapping off the dead flower trusses to prevent the development of seeds, which take a great deal of strength from the development of the following year’s flower buds.

Break out only the spent blooms to avoid damaging the dormant buds.

What Is Disbudding in Rhododendrons?

Another form of pruning is called disbudding. It involves pinching out the terminal leaf bud on new growth, thus awakening dormant buds and causing side branches to appear. Disbudding is typically performed on new growth and can be repeated in the fall.

Be careful not to break off a flower bud. Disbudding is a useful technique in shaping plants or making them more compact.

Common Rhododendron Problems in South Carolina

Rhododendron pest and disease issues are usually preventable with good cultural practices.

Rhododendrons are susceptible to a wide variety of pests; however, when properly sited, planted and maintained, pest problems are limited. Following two to three years of establishment, rhododendrons require very little maintenance and are relatively pest free.

When problems do arise, take care of them immediately, before they get out of hand and worsen or spread to other shrubs.

Rhododendron Diseases

Diseases might include root rot, blight and dieback.

More information on rhododendron diseases is available in the fact sheet HGIC 2050, Azalea & Rhododendron Diseases.

Common Insect Pests on Rhododendrons

A few common insect problems include lace bugs, mites, and scale.

Borers are an occasional, but serious, problem. Homeowners should be on the lookout for this pest.

More information on rhododendron insect pests is available in the fact sheet HGIC 2051, Azalea & Rhododendron Insect Pests.

Rhododendron Hybrids for South Carolina Landscapes

Rhododendron hybrid varieties offer improved heat tolerance and performance across South Carolina.

Hybrid rhododendrons are generally considered more adaptable to various garden and climatic conditions. The crossing of two or more parents gives us a wide range of adaptability from which to choose.

The “ironclad” hybrids have proven to be the most cold hardy and often the most heat resistant of the hybrids. Many of them are descendants of our southern native Catawba rhododendron (R. catawbiense).

The hybrids listed in Table 2 are among those that do well in South Carolina.

How to Select and Purchase a Rhododendron

Selecting high-quality rhododendron plants ensures better establishment and long-term health.

When planning to purchase a rhododendron, visit or order from a reliable nursery and select a named variety. The shrub should be well-branched, with four or more limbs close to the ground.

Look for self-rooted plants; grafts are not desirable in this case. The native species are suitable in many areas. A variety with R. catawbiense parentage is usually reliable here, as are the “ironclads.” Chapman’s rhododendron (R. champmanii) is very good for coastal areas.

Evergreen Rhododendron Species for South Carolina (Table 1)

The following evergreen rhododendron species grow well in various regions of South Carolina.

Table 1. Evergreen Rhododendron Species Commonly Grown in South Carolina

Species	Region¹	Characteristics
Carolina rhododendron (R. carolinianum)	M, P	Three to 6 feet tall after 10 years; similar or greater spread. The most common flower color is pale lilac rose; some plants are pure white or pink, and they bloom late². One of the hardiest native evergreen rhododendrons.
Catawba rhododendron or purple laurel or mountain rosebay (R. catawbiense)	M, P	Four to 6 feet tall at 10 years; usually wider than tall; varies from compact to loose growth. Lilac-magenta flowers late in the season²; 14 to 20 blooms in a rounded truss. Considered by many to be the finest of all native American shrubs. Rhododendron growers know it for its extreme hardiness and as the parent of our most hardy hybrids.
Chapman’s rhododendron (R. chapmanii)	All	Three to 5 feet tall at 10 years; broad, upright, rounded shrub. Pale pink to rose flowers; late season². Heat tolerant.
Rosebay rhododendron or Great Laurel (R. maximum)	M, P	Four to 12 feet tall at 10 years; loose and open habit. White to pink blooms appear late to very late in the season² and are often hidden by new growth. Flowers are smaller than Catawba rhododendron. Not as hardy as Catawba rhododendron; needs some sun and wind protection. Use as a background shrub.
Piedmont rhododendron (R. minus)	M, P, SR	Up to 8 feet tall after 10 years; a loose, upright plant. Flowers are generally bright lavender rose, although some are pale pink or salmon pink. Blooms late, a few weeks after Carolina rhododendrons. Heat tolerant; requires plenty of shade. Use in wooded areas.
1Regions of South Carolina: M = Mountains; P = Piedmont; SR = Sandhills and Ridge; CP = Coastal Plains; All = Entire State. 2Seasons: Early = early spring; midseason = midspring; late = late spring; very late = summer.

Recommended Rhododendron Hybrid Selections (Table 2)

These hybrid rhododendrons offer heat tolerance, cold hardiness, and reliable performance across the state.

Table 2. Recommended Rhododendron Hybrid Selections for South Carolina¹

Hybrid	Characteristics
‘Album’	Grows to 6 feet; tough and vigorous. Midseason² blooms, lilac opening to pure white with greenish-yellow spotting.
‘Anna Rose Whitney’	Grows to 6 feet; needs plenty of room. Deep pink flowers in mid- to late season²; heat tolerant.
‘Caroline’	Grows to 6 feet; heat tolerant. Slightly fragrant lavender-pink flowers; mid- to late season². Considered resistant to root disease.
‘Cynthia’	Grows to 6 feet; heat tolerant. Blooms midseason²; rosy pink.
‘English Roseum’	Upright plant to 6 feet; heat and cold tolerant. Light lavender-pink flowers; midseason².
‘Ginny Gee’	Grows only to 2 feet. Heavy flowering; early to midseason²; pink to white flowers.
‘Janet Blair’	Grows to 6 feet; vigorous. Blooms mid-to-late season²; lavender-pink with greenish throat.
‘Lee’s Dark Purple’	Grows to 6 feet. Blooms mid- to late season²; dark purple.
‘Nova Zembla’	Grows to 5 feet; heat and cold tolerant. Blooms mid- to late season²; red. Heat resistant.
P.J.M. hybrids	Grows to 6 feet; heat and cold tolerant. Blooms early season²; bright lavender-pink.
‘Roseum Elegans’	Grows to 6 feet; vigorous, fast-growing. Rosy-lilac bloom in midseason². Extremely heat tolerant.
‘Scintillation’	Grows to 6 feet; rounded, vigorous shrub. Blooms mid-season²; pink with goldish brown throats.
‘Vulcan’s Flame’	Grows to 5 feet; heat resistant. Blooms midseason²; bright red flowers.
1Best suited for Mountains, Piedmont, and Sandhills and Ridge regions. 2Seasons: Early = early spring; midseason = midspring; late = late spring; very late = summer.

Adapted from Rhododendrons in Alabama, by R. Shumack, Alabama Cooperative Extension Service Circ. ANR-151.

References

1. https://plants.ces.ncsu.edu/plants/rhododendron/
2. https://scholar.lib.vt.edu/ejournals/JARS/v4n4/v4n4-bowers.htm
3. https://fsus.ncbg.unc.edu/main.php?pg=show-taxon.php&plantname=rhododendron

Document last updated on 11/25 by Jordan Franklin.

Originally published 11/00