Rhododendrons are popular among gardeners with their evergreen shrubbery and early blooms.
Also receive the 蜜桃恋人 Daily newsletter including gardening tips, weather, astronomical events, and more.
Planting, Growing, and Pruning Rhododendrons and Azaleas
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鈥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.
鈫 Not sure which hardiness zone you鈥檙e 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 鈥渕ulch volcano,鈥 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鈥 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鈥檚 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.
Catherine Boeckmann
ADVERTISEMENT
have annual argument with lawn mower fellow; he thinks the more leaves under the rhodos the better almost 4 feet, easier for him to blow leaves under shrubs than take them away,
thanks for help
While leaving a thick layer of leaves under trees and shrubs can provide a nice winter mulch, 4 feet is too much of a good thing! About a foot is all that is needed to reap the benefits. When the pile gets so high as to cover crowns and trunks, it can potentially lead to rot as the leaves get wet with winter weather. Also, such a high pile provides habitat for undesirable critters such as rats. You are right … he should be taking some of the leaves away.
What would be the cause of an outbreak of white mushy globules on the wood and branches of a pink flowering rhododendron? The shrub is 30+ years old and at least 15 foot tall, it has not been looked after by previous owner for many years, it gets morning sunshine but is protected from harsh afternoon sun. Many thanks, Pam
Hi, Pam, This sounds like azalea gall (to which rhododendrons are also susceptible). Gall is a fungus, spread by rain. It normally occurs during cool, wet weather. If this is gall, you can pick it off by hand; fungicides can be applied. See you local organic nursery supply store. You did not mention the leafs; these typically curl up when fungus is present.
By the way, even though the plant gets a fair amount of sun, its bed could retain dampness, which can be a contributing factor.
We suggest, if possible, you take a sample of the globules and a photo of the plant to your local nursery. They may be able to identify this in a jiffy.
And remember, too: This is a good time to spread some aged manure and compost under the shrub. As the saying goes: 鈥渋n the fall or not at all.鈥 Stir up the existing soil and work the new matter it, if you do this鈥攂ut be gentle. Rhodo roots tend to be shallow.
We hope this helps.
Many thanks for your reply concerning my ailing plant. It would appear that the only remedy is to throw away the deceased rhododendron, which is a great pity, it was a beautiful flowering plant and only a year old. But thanks again for your advice.
Hi, we have a white Rhodo which we had to move in April because of building work, since the move it has thrived and has beautiful green healthy leaves and has grown about 4 inches, it is also flowering, my question is, should it be flowering at this time of year and will it affect the flowering of it for next year?, the buds on it at the moment look really strong and healthy!! Great site.
It could be blooming now because it was delayed from doing so in the spring during the transplant. As long as it remains healthy and it has been able to reestablish a good root zone, there is no reason to think next year’s blooms won’t be just as enjoyable.
Is this normal ? Just worried it might start flowering.
Thanks
Rick
Despite applying a compost recommended for rhododendron and ensuring that the soil is acidic, the leaves continue to droop and die.
Your shrubs could have Verticillium Wilt, which is a disease caused by fungal spores in the soil. Unfortunately, it is very difficult to get rid of. The general recommendation is to take out the plant once it succumbs, dig out as much of the soil as is feasible, replace it with clean soil, and replant with a species not susceptible to the disease (not another Rhododendron).
