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How to Grow and Care for Rhododendrons



Rhododendrons are a fantastic evergreen flowering shrub which throws of tons of blooms throughout the spring and early summer.

When referring to rhododendrons being evergreen, that's in reference to the two main species planted by gardeners, which are of the subgenus Hymenanthes (elepidote) and rhododendron (iepidote).

There are a few varieties of the subgenus iepidote which are semi-deciduous, but most of those aren't grown by gardeners.

Deciduous rhododendron are in the subgenus pentanthera, which are what we identify as azaleas. For the unitiated it can get a little confusing at times.

Those plants the majority think of when contemplating rhododendrons are of the subgenera Hymenanthes and Rhododendron.

The leaves of a rhododendron in the subgenus Hymenanthes have larger leaves than those of the subgenus rhododendron, which also have more of a scaly look.

Incredibly, rhododendron varieties can grow anywhere from about four inches tall, with a few varieties growing all the way up to about 100 feet tall.

In this article we're going to look at how to grow the two more commonly planted of species of rhododendron. So when the tips are given, they'll embrace what almost all gardeners consider rhododendrons.

Rhododendron Blooms

Regardless of the varieties and characteristics of rhododendron, including leaves and sizes, there's one thing that sets it apart in the heart and mind of gardeners, and that is their gorgeous and prolific blooms.

Before we get into the how part of the article, let's look at a few of the extraordinary types of blooms this amazing shrub offers to gardeners.

Pink Rhododendron Flower Photo

Sun Fire (Pink and Yellow) Rhododendron Flower Photo

Blue and Orange Rhododendron Flower Photo

White and Pink Rhododendron Flower Photo


Gorgeous and Elegant Rhododendron Flowers

After viewing these stunningly beautiful rhododendron flowers, you can see why they are so desirable to grow, and well worth the effort.

Now let's get into how to have a bouquet of these extraordinary flowering shrubs displaying their color in your yard or garden.

Growing Rhododendron from Seed

There are a relatively small number of plants that a gardeners shouldn't attempt to grow from seed, and one of them is the rhododendron.

In this case it's not because it's hard to do as far as germination results go, but because it can take up to ten years for some rhododendron plants to bloom if started from seed, depending on the variety. Some may bloom as early as two years after planting.

Unless you're the type that likes to experiment with things over the long term, there simply isn't any reason to grow rhododendron from seed.

Who wants to wait for those gorgeous blooms for any reason? Again, unless it's a project because of a curiosity or wanting to observe the process over the years, don't waste time trying to grow rhododendron from seed.

Other than acquiring a plant, the other ways to propagate rhododendrons are from cuttings or grafting. I would recommend acquiring a rhododendron and transplanting it. It's quick, easy, efficient, and brings the quickest results. Isn't that what we all want with our flowers?

When to Plant Rhododendron

Rhododendrons can be planted at any time without too much difficulty, but the optimum times to plant are in the cooler months of early spring or early fall. This will produce the best results for the plant over the long haul.

Planting in warmer months could result in the plant going through more stress, which could affect it in a way that takes it longer to successfully establish itself.

Where to Plant Rhododendrons

Rhododendrons grow best when planted in partial shade. The caveat to that is how much shade dependent upon what part of the country you live in.

If you live in a cooler region, the shrub can take more sun, while in the warmer regions it prefers more shade.

Some writers assert it can be planted in complete shade, but it will suffer drastically if that is where you plant it. Rhododendrons do need some sun for best results.

Another factor in where to plant rhododendrons is their exposure to the wind. Some regions may not be a vulnerable as others, but it is a good idea to plant them in an area with some shelter from heavy winds if possible.

Next to the house or maybe near the edge of a tree line are a couple ways to do it. A low lying area is another possibility, although it will need to drain well for the plant to thrive, as the flower likes soil to be moist, but not too moist.

Rhododendrons - Growing and Planting

How to Plant Rhododendrons

When you are ready to plant your rhododendron, dig out a hole about the depth of the plant, and about twice the length of the root ball. Some gardeners will dig the hole a little smaller than that; just a little larger than the length of the root ball.

The reason for digging the hole larger is to add organic matter to the sides of the plant before filling in the hole. Those going with a smaller hole don't feel the need to do that.

Before you place the plant in the hole, it is absolutely necessary to break apart the root ball if you want success. When you tap around the pot to loosen the plant from the container, you'll find when you look at the roots that they are smooth and hard.

You must cut into and loosen the roots to allow them to escape and grow. Cutting into the root with a simple kitchen knife is one way to do that if it is really hard, or you can scrap a garden tool against it to loosen up the sides and then use your hands to break it up.

Obviously leave the root as intact as much as you can, although losing a little of it won't matter as the root system is very hardy on the plant.

It's more important to break up and loosen the root system than try to keep the entire root ball intact.

Now place the plant in the ground at least at soil level. Most gardeners will add some soil on the bottom of the hole in order to have the plant sit an inch or two above the soil line before filling it in. Some gardeners keep it level. I think it's best to have it a little above the ground line.

How to Plant a Rhododendron

Making the Soil More Acidic

Rhododendrons love acid, and it's worth checking the acidity of the soil to ensure it will thrive. A pH in a range of about 4.8 to 6.5 is best for the plant. Approximately 6.0 or a little under is ideal if you can accomplish that.

If your soil is higher in pH, amend it until it brings it in line with the demands of the shrub.

Another trick is to use pine needles as mulch, which over time will add acidity to the soil as well. You should do this in conjunction with the soil amendment.

Leave a few inches bare around the base of the rhododendron when adding the mulch.

Pine mulch also protects against some pests which won't travel over the prickly needles.

Fertilizing Rhododendron

Rhododendron will only need to be fertilized a couple of times a year at most.

When fertilizing the plant, use the same type of fertilizer you would use for azaleas; one with a rich acid base to it. After fertilizing you can water the plant to help push it down into the root system.

Application of the fertilizer should be around the drip line and root ball of the plant for best results.

Assuming other things are done correctly, all you have to do is watch the performance of your rhododendrons and let their foliage and blooms tell you if it needs some fertilizer.

Best times to fertilize rhododendrons are in the early spring or latter part of winter.

Do read the labels of the fertilizer carefully, as rhododendrons don't require as much fertilizer as other plants.

In cooler climates you should apply fertilizer in the latter part of June because it could encourage new growth which cold winter weather would harm.

Pruning Rhododendron

Because rhododendrons are hardy and prolific, there will come a time that you'll probably need or want to prune the plant to give a more appealing look.

Although it's not a difficult task, you do need to know what you're doing for the particular variety of rhododendron you plan on pruning. The key is to not cut it back too much or you could be cutting off the blooms for the next year or two, losing the beautiful color.

For this reason, some people recommend not pruning rhododendrons at all, and allowing them to grow naturally in any way they want.

It think this is an over-response because of those who don't do a little homework who have ended up harming their plants. The key is understanding and knowing how to properly prune the particular variety you are growing.

For example, some varieties have nodes or buds all over the branches, making it irrelevant where to trim the shrub. All you need to do there is prune it in a way that is aesthetically pleasing and not so deeply that it interferes with the performance of the plant going forward. This is mostly in reference to established plants.

Having said that, most rhododendrons need to be cut a little above a bud or node to ensure blooming the next year. It can't be done haphazardly.

The best time to prune rhododendron is right after they bloom; in the latter part of spring or the early part of summer.

In the middle part of summer, or in some cases the latter part, rhododendron will begin to set buds. So it's best to prune them before the buds for the following year emerge, providing the most favorable condition for the plant to produce blooms the following flowering season.

Best practices is to cut the shrub about a quarter of an inch above the chosen bud or node. That encourages the growth of the branches, and by extension, more flowers.

Pruning and Deadheading Rhododendrons

Rhododendron Care

Care of rhododendron is almost totally centered around its root system.

The same reason it needs to have the root ball broken up when planting the plant, is the same reason you have to carefully watch it for watering needs.

This is a reference to the thin and shallow roots of the plant. The thin roots takes time to break free of the root ball and into the surrounding soil, even after being broken up.

That means as far as watering goes, it will draw primarily on the water available to its immediate roots, as it won't be drawing any water from extended roots yet because they won't extend far enough in the first season to make a difference. The reason why is the fineness of the roots result in the plant taking longer to grow its roots out to gather up water.

As for care, this means in the first season the plant will need to be more carefully watched for water needs. Once it's established this isn't too much of a problem for the plant. So in the summer months during the first season the plant will need more watering than it will in the subsequent years.

Don't be fooled into thinking because some of the surrounding soil is wet that the plant is drawing moisture into itself during the first year. Just picture the underground root system being as long as when you planted it to visualize how far they are extending out into the surrounding soil. Consequently, the plant may appear to be drawing in water, but in fact is dry because of its short roots. Remember, we're talking the first season only.

If you have older rhododendrons in the yard, don't think in terms of the younger plants having the same needs as they do, because they will have a deeper and extended root system which is drawing water into itself.

Watering Rhododendrons

With these root challenges, how do you identify when your younger rhododendrons really need water?

I pose that question because all rhododendrons can have some of their leaves drooping in times of drought, even established ones.

If your plants are drooping in the morning before it gets hot, it's a sure sign the plant needs to be watered. Be sure to give them a good drink if that's the case. Your first-year plants need to be watered close to the plant's root system for the reasons mentioned above. Take time to water it a little at a time, allowing it to gradually soak in and not just drain off to the side, which will be useless for the needs of the plant.

Another effective measure is to place a dripping hose at the base of the plant for a few hours, which will produce similar results without you needing to be there.

Mulching also helps retain moisture for you new plants, along with the other benefits of the practice.

Shallow Roots

Watering aside, the shallow roots of the rhododendron provide another challenge.

If you start to have some weed problems, you shouldn't do any cultivating around the immediate plant base because you can do damage to the shallow roots.

Assuming you've effectively mulched the plant, and only have several inches around the base which is an issue, you can cautiously pull the long weeds out if they don't offer too much resistance, or you can carefully cut them off at ground level with a hoe or other tool. Usually pulling them up should work, although, depending on the weed type, there can be times when it could disrupt the root system if you pull the weed out manually.

Protection During Cold Months

Location is a big part of protecting your rhododendrons during the winter, so original placement is important.

As mentioned earlier, this is mostly referring to protecting your plants from heavy winds.

Excessive sun is another issue, so planting in partial shade deals with that potential problem.

Another somewhat unknown and neglected aspect that research has shown is when the plant is fertilized in the manner it should be, it results in the plant resisting the effects of winter and cold winds on the plant.

Finally, some varieties perform better in the winter than others, so check them out to see if they will perform better in the winters of your particular region or zone.

If you have no natural wind barriers, or if you aren't able to plant them against the house or other place with a barrier, you can build a wind barrier yourself to protect your investment.

Rhododendrons and Disease

The best way to prevent disease in rhododendrons (which is usually rare), is to practice prevention, rather than waiting to fix problem resulting from poor practices.

Most diseases inflicting the plant won't come about if you keep the plant healthy.

This involves planting the rhododendrons in soil that drains well, mulching the plant, fertilizing correctly, keeping area around the plant clean of debris, protecting from the cold, watering when needed, and pruning dying stems as needed.

Do this and you should enjoy very healthy and disease-free plants.

If your rhododendrons do contract a disease, take care of it as soon as possible with the appropriate controls.

Insect Management

Similar to diseases, rhododendrons don't have a lot of problems with insects, but when they do, most of the time it's more of a local situation; depending on the particular pests living in the region.

For that reason it's almost impossible to offer a general solution to the relatively rare problem.

It's best to contact your local extension agent or master gardeners to find out the best way to treat the pest problem.

Healthier plants offer more resistance, so similar practices which battle against diseases also work for preventing or limiting insect infestations.


Even though there is a lot of detail in this article on the growing and care of rhododendrons, much of it is to cover most of the best practices and probable problems accompanying growing this magnificent plant.

Planting it in the right area and watering it correctly in the first year will take care of the majority of the problems associated with the plant, and most gardeners will not need to do much at all over the lifetime of the rhododendron other than pruning it to the desired shape and size, which will encourage it to bloom even more.

Rhododendrons are among the most gorgeous, inspiring, beautiful and bountifully-blooming flowers we can grow, and we owe it to ourselves to have this extraordinary flower coloring up our landscape for all to enjoy.


Kelly Kline Burnett from Madison, Wisconsin on July 17, 2012:

I planted some from Home Depot last fall - wonderful shrubs! I was considering planting more but the drought has been daunting. I pray this dry streak ends for the sake of my trees and rhododenrons.

The Logician from now on on May 08, 2012:

Just an awesome hub! Maybe, just maybe I can grow some now!!

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