Rhododendrons are popular among gardeners with their evergreen shrubbery and early blooms.
Planting, Growing, and Pruning Rhododendrons and Azaleas
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Planting
Most large-leafed varieties require dappled shade; avoid deep shade or full sun. A sunny spot that receives a few hours of shade is perfect. See regional guidelines below.
Soil should be well-drained, humus-rich, moist, and acidic (pH 4.5–6).
Azaleas and rhododendrons have shallow root systems and need moist soil and mulch to keep them from drying out. Amend planting areas with compost, peat moss, or a substitute, only if your soil is poor. Learn more about soil amendments and preparing soil for planting.
→ Not sure which hardiness zone you’re in? See the USDA map.
Planting in Cold or Temperate Regions (Zones 3 to 6)
- Plant in full sun to increase flowers and avoid mildew problems. Shrubs need a minimum of 6 hours of full sun daily.
- Plant on the sheltered side of a windbreak. If subjected to cold, dry winds, their leaves and buds dry out and die, especially during winter winds.
Planting in Warm or Hot Regions (Zones 7 to 11)
- Plant in a site that receives afternoon shade, especially in hot areas. In tropical zones, azaleas will bloom in full shade.
How to Plant Rhododendron & Azaleas
- Plant in spring or early fall.
- Space plants 2 to 6 feet apart, depending on their estimated mature size. Dig a hole as deep as the root ball and about twice as wide.
- Set new plants so that their top roots are at soil level or slightly below. If you plant them any deeper, the roots and trunks may rot.
- Fill the hole half full with soil, then water it well to settle the soil before filling it with the remainder of the soil.
Growing
How to Care for Rhododendron & Azaleas
- Mulch plants every spring with 2 to 5 inches of pine bark chips or pine needles to protect shallow roots and retain soil moisture. A lack of water reduces flower bud formation. Read more about using mulch.
- Tip: A common mistake is to create a so-called “mulch volcano,” where mulch is piled heavily around the trunk of the shrub. In fact, this can keep the trunk too wet and encourage rot. Always leave a few inches around the trunk free of mulch.
- See our guide to using mulch.
- Fertilize azaleas and rhododendrons sparingly and only when flower buds swell in the early spring, even if they are fall bloomers. Heavy applications of fertilizer will burn the plants’ roots.
- Water plants during the summer if rainfall is less than 1 inch per week.
- After flowering, deadhead where practical, to promote vegetative growth rather than seed production. Remove dead flowers from rhododendrons carefully; next year’s buds are just under the old heads and will start to develop shortly after flowering.
- Azaleas and rhododendrons may be transplanted at any time during the growing season, but they transplant most successfully during fall or early spring when they are dormant and temperatures are cool.
Winter Care for Rhododendrons
Rhododendrons are shallow-rooted plants; in cold regions, apply several inches of organic mulch around the base. In regions with severe winters, consider wrapping evergreen rhododendrons with burlap in the fall. Cold, dry winds will cause too much moisture evaporation from the leaves, which will wither and die. To help them recover from cold snaps, deeply water rhododendrons if there are warmer days. In the spring, prune out any dead or damaged branches and leaves.
Pruning Rhododendron & Azaleas
- In general, do not prune spring-flowering shrubs such as azaleas and rhododendrons. If you need to reduce height, prune after flowering in the spring.
- Otherwise, just remove dead, damaged, or diseased branches at any time of year.
- On young and old plants, simply snap off spent flower stalks by bending them over until they break away from their stems. Be careful not to damage growth buds at the base of each flower stalk.
There are more than 900 species in the Rhododendron genus, which vary greatly. It would take a whole book to understand this wide world!
You may be interested in joining the American Rhododendron Society, which runs a database with information on more than 2,000 rhododendrons and azaleas. On an annual basis, the society selects a number of rhododendrons to be awarded the Rhododendron of the Year designation, highlighting the best-performing plants for different regions.
Here is a handful of varieties that we think you’ll enjoy:
- ‘Blue Diamond’ is a dwarf evergreen rhododendron that grows to 3 feet. It blooms mid-season with violet-blue flowers. Zones 7 to 9.
- ‘Cecile’ is a vigorous azalea that grows to 7 feet and produces dark salmon-pink buds in mid-season. Zones 5 to 8.
- ‘Hydon Dawn’ is a low-growing rhododendron that actually tolerates full sun. Pale pink flowers bloom in mid-season. Zones 7 to 9.
- ‘Nova Zembla’ is an evergreen rhododendron that grows 5 to 10 feet tall and bears bright red flowers in late midseason. Zones 5 to 8.
- ‘Rosy Lights’ is an azalea that offers extra cold hardiness. It grows to 6 feet and bears deep purple-pink flowers. Zones 3 to 8.
- ‘Purple Gem’ is a dwarf rhododendron that grows to 2 feet and is an early-season bloomer. It bears small, light purple flowers. Excellent in front of a border or in a rock garden. Zones 5 to 8.
Catherine Boeckmann
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We would recommend consulting the American Rhododendron Society website and looking through their catalogues of species!
I have a RHOADY which is only 4 feet tall and all the leaves are wilting above the 3 feet and everything lower than 3 feet are perfectly heathly and have started to bloom. Any idea what caused this?
I have two large rhododendron trees that were planted more than 20 years ago and this year in the winter one of the four main trunks split because of the weight of the snow should I be removing the whole section or should I leave it alone and see what happens in the spring?
It would be wise to leave it alone through winter, as the tree is heading into dormancy and won’t be able to mend itself until spring. For now, consider wrapping the injured part with a tree wrap to protect it from the elements of the season. Then, see how the tree looks in the spring—mainly if the broken section has died or not—and proceed with pruning from there.
We planted five Rhododendrons on our East facing slope in front of our house on Contra Costa county California. The two white rhododendrons have terrible sunburn on their leaves. I am misting them daily to get them through the summer, but should I remove the burned leaves?
Yes, you can remove the yellowing or brown leaves, since those leaves won’t recover. Beyond misting, make sure that you are watering the rhododendrons consistently and deeply to keep them hydrated. Also, only spray or mist the plants in the morning or evening; doing so in the afternoon can actually increase sunburn of the leaves.
We bought a property with giant rhododendron shrubs. We also have azaleas. This is our third summer and we are not seeing much flowering. We have new growth but the buds are opening to a bunch of leaves, not flowers. I found miracid in the garage and think maybe we should be fertilizing. There is a good 4-6" in pine needles and oak leaves under these. Do I need to remove the leaves for the fertilizer to reach the plant roots? I know the pine needles are good for them.
I live in Warminster, Pa., just 15 miles northeast of Philadelphia. I believe my home is positioned southeast. My front door faces east and I have full sun from sunrise till about 1-2 PM. There is corner at the end of my porch which is bare. My plans were to put in a
rhododendron bush in that spot. My daughter tells me they are shade plants. Who is right?
I read somewhere these plants need 6 hours of sun. Thank you for your help.
Please see the Planting section of this page (above) for advice on where to plant rhododendrons and what kind of lighting they prefer.
You are likely in Zone 7a, which gives you a lot of options when it comes to gardening! See the USDA hardiness zone map here: https://planthardiness.ars.usda.gov/PHZMWeb/
I forgot to ask in my previous comment, what time zone do I live in? I always planted my annuals after Mother's day because I was not sure of my time zone.
