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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If it doesn’t seem root-bound or stressed, you can leave it in the pot until spring, but keep it outside in a protected area (like up against the house) and put a thick layer of much around its crown. The main thing is to let it experience the cold so it goes fully dormant.
I have azalea plant in the pot it came in. I've had it since February. I am moving to NH and want to plant it there. Should I keep in pot till spring or can I plant in mid November? Plant has special meaning. Thank you
This May of 2016 I planted 1-Rhododendron and 3 Blackeyed Susans. The Blackeyed Susans are in front of the Rhododendron. The Rhododendron stopped flowering by July and the petals dried up. Then the Blackeyed Susans started to flower,grew both in height and width, and now block out the Rhododendron. Since this is the first year for the plants, how do I prune,thin or cut back both plants to get ready for next year growing season. Also,should I fertilize them now and what type of fertilizer
Hi Bob,
Don’t prune the rhodie; it needs to get established. As for the black-eyed Susans, they are perennials and should be cut back to the ground when they die off for the season (typically late fall). Ultimately, the shrub will outsize the perennials and you will have a nice underplanting. The fertilizing season is winding down so don’t worry about that until spring. Look for slow-release granular fertilizers formulated for rhododendrons.
Can you prune the azaleas all the way back?
Azaleas look best when pruned consistently and minimally every day (removing dead limbs). However, if your azalea is overgrown, yes, you can prune azaleas down to about 1 foot in height.
I have had three rhododendrons on the side of my house for around 17 years. They have thrived however this year the leaves turned brown on one of them, while the other two still look good. We were concerned it had died but recently it has had some new green leaves on the bottom branches of the plant. Any thoughts on what could have caused this and what we can do to help it come back?
Hi, Kathryn, “Rhodos” are pretty resilient but occasionally they get sick. The wilt or browning that you describe could be caused by several things, such as poor drainage (is this plant more vulnerable to pooling water than the others?), summer drought (oddly enough, too little water is about as damaging as too much), accumulated fertilizer that did not wash into the soil (see poor drainage above), being planted too deep (on the face of it this may not sound like your plant…but if water runoff or the like has carried soil/silt or mulch to the plant and that built up on the roots, it is as if the plant is buried too deeply; the roots should be near the surface of the soil/ground)
It sounds like your rhodo is in recovery, Perhaps you can help it along by checking on these points.
Thanks for asking! Hope this helps—
