Caption
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.
Types
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.
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Hi, Robert,
If you are in a moderate climate, you can plant almost any time. In a cold climate, the ideal time to plant is early spring; early fall is second choice. (You want to give the plant time to adapt.) In a hot climate, plant in fall (so that the plant has time to adapt in the cooler portion of the year).
Rhododendrons are common in foundation (near the house) plantings. Take into consideration how tall and wide it will get (or how tall you want it to get; note that controlling its size will require pruning). You can learn more about this on the plant tag, possibly from the vendor who sold it, or be doing a bit of research on the particular variety you have.
We hope this helps!
Hi, Kay, Some deteriation—leaf drop or droop—is not uncommon after a hard winter. Keep them well watered in well draining organic soil, and layer on some rich, organic mulch.
The film may be powdery mildew. It is grayish white and powdery; you have not menitoned a color. Iif it is powdery mildew, it could be caused by high humidity.
It also could be a local insect. You will do best by consulting a local nurseryman or cooperative extension service or a master gardener; the latter can often be foudn through a garden club.
Sorry we can't be more specific.
Hi, Roger! Thanks for your comment. Hope we can help... A initial consideration for almost any failure to thrive is soil quality and pH. Rhododendrons and azaleas prefer acidic soil. That's another way of describing the pH, and pH can be checked with an inexpensive soil tester. A good nurseryman/woman or your local extensive service can help you with that, too.
Rhodos and azaleas also like organic material in the soil and organic mulches on top. As noted below, give the plants a good dose of aged manure in late fall (or not al all). Fertilizer specifically designated as for azaleas is also recommended, but only in later winter or early spring.
Also, keep the water coming, especially in warm, dry periods.
We wish you the best!
It's not likely the the tree roots killed it. Every plant has a period of adjustment to its new home/location. You do not describe what "dying" looks like but some foliage droop is normal in dry, warm afternoons. If the leaves are drooping in early morning, it needs water.
Watering it is good; keep doing that. Also mulch it with organic material—leaves, pine needles, wood chips or the like—to maintain moisture and eliminate the need or desire to cultivate the ground.
Spread aged manure under the plant in fall—or not at all. IN other words, do not do this at any other time.
Finally, if you continue to have problems (or after reading this), contact the source, the place from which you bought it, and ask if they advise any particular care.
Hope this helps!
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