Caring for and pruning Rhododendrons

When we bought our house there were many perennial flowers and bushes planted throughout the backyard. One one side were 2 azalea bushes and on the other side was 1 rhododendron bush that has tripled in size over the last 10 years! My husband hates that big thing! lol I love it though and it seems like the less I care for it the better it does. Pretty much the only thing I do to care for the rhododendron is to toss some bird seed under it every few days in the summer.

How to prune and care for rhododendrons

Ok, that sounded weirder than it actually is! I have chickens and the little ones like to go under the rhododendron bush. They hide from the adult chickens under there. Obviously while they're hanging out they poop from time to time which delivers a nitrogen rich fertilizer right above the roots. If I didn't have chickens adding fertilizer I would have to do it manually, but as it is chicken manure is great for fertilizing plants!

Thankfully chickens don't usually eat things that are bad for them which is a good thing since rhododendrons are poisonous to people and animals.

Obviously I didn't choose either plant but if I had I would have picked the rhododendron. I prefer it's flower clusters and size to the azaleas, they are mighty similar though and there's a good reason why.


All azaleas belong to the Rhododendron genus, but not all Rhododendrons are azaleas. No wonder they are so similar! I will tell you that all of my plants are in the same type of location with the same care and the rhododendron is doing much better! It probably gets slightly more sun though so that might account for the differences. 

It's hard to talk about one without the other so the lines will be blurred a bit as I discuss caring for the rhododendron. Their care is the same though, so this info applies to either.

Rhododendrons are broadleaf evergreens and are propagated over bottom heat in early winter. Azaleas can be either evergreen or deciduous. Deciduous Azaleas are known as Mollis or Exbury Azaleas. Evergreen Azaleas are known as broadleaf evergreens because they do not have needles. They bloom later in the spring, and are usually propagated in the fall over bottom heat. 

Here's a good explanation on using bottom heat to propagate cuttings. But I'm getting ahead of myself! Let's talking about caring for rhododendrons.

Caring for rhododendrons

Keeping Rhododendrons healthy and happy is as simple as understanding what they like. First of all, they like to grow in a climate that suits their tastes. Many varieties don’t like it in the north, and to prove the point they will up and die as soon as extreme cold weather hits. Buy plants that are known to be hardy in your area. Mine freeze tight every winter and are perfectly fine in spring because they are hardy in our temperatures.

Here in zone 5 (western Pennsylvania) you can find several different Rhododendrons that do well even with the bitter cold and snow that we get. Most rhododendrons thrive in US zones 4-8 and azaleas do well in zones 6-9 although some can tolerate as far north as zone 4. Make sure to check the tag when choosing a new plant at the nursery or home store before choosing a plant.

How should you fertilize Rhododendrons and Azaleas? These broadleaf evergreens are laid back and like to take it slow and easy. Do not fertilize them with quick release nitrogen fertilizers, it could kill them. Instead give them an organic snack, like Milorganite or well rotted cow manure or compost. Or attract your chickens to them to play and poop underneath, it works for me!

The acid rumor: A long time ago somebody let the word out that Rhododendrons are acid loving plants, and people are always thinking their struggling Rhododendron needs more acid. The answer is usually not acid. Your struggling Rhododendron probably needs a great big gulp of oxygen around its root system.

Rhododendrons do not like wet feet. They don’t even like high humidity let alone wet soil around their roots. They like to be high and dry, and love to have an unobstructed flow of oxygen to their roots. You can accomplish this by planting them in a bed raised at least 10” with good rich topsoil. They will be smiling from branch to branch.

They do well in the shade, but contrary to popular belief they do even better in full sunlight. That explains why the rhododendron in the sunnier area is doing better than the 2 azaleas in the shade...remember, they're sorta the same. Both shrubs make a great addition near the vegetable garden as they attract a lot of pollinators like butterflies and bees.

Large rhododendron bush

Pruning rhododendrons 


I don't often prune mine, but the best time to prune Rhododendrons and Azaleas is in the spring right after they bloom. These plants start setting next year’s flower buds over the summer, and late pruning will cost you some blooms next year, so get them pruned as soon as they finish blooming. 

It’s also a good idea to pick off the spent blooms so the plants don’t expend a lot of energy making seeds, unless of course you’d like to grow them from seed. But keep in mind that they don’t come true from seed. For example, seeds from a red Rhododendron are likely to flower pale lavender. Cuttings ensure a duplicate of the parent plant. Use the method I mentioned up above for best results.

Pinching is a low impact form of pruning that is very effective for creating nice, tight full plants when you are growing small plants from seeds or cuttings. Typically a Rhododendron forms a single new bud at the tip of each branch. This new bud will develop into another new branch, another bud will form and the process will continue. If left alone this will produce a very lanky plant with a lot of space between the branches, forming a very unattractive plant.

If you are starting with a plant that is nothing more than a rooted cutting all you have to do is pinch off this new growth bud as soon as it is about 3/8” long. Just grab it between your fingers and snap it completely off. When you do this the plant usually responds by replacing that single bud with two, three, or even four new buds in a cluster around the bud that you pinched off. 

Each one of these buds will develop into branches and eventually a single bud will appear at the tip of each of these branches, and of course you should come along and pinch each one of those off, forcing the plant to produce multiple buds at the end of each of these branches. The more often you pinch off these single buds, the more branches the plant will form, making a nice, tight, full plant. 

Pruning rhododendrons

Pruning larger plants: Believe it or not, you can use hedge shears!!! The result is a very tight compact plant loaded with beautiful flowers. Rhododendrons trimmed in this manner become so tightly branched that you cannot see through them, and that is the result of vigorous pruning with hedge shears. Sure you can use hand shears, and you’ll have a nicer plant because of it, but you can use the hedge shears if that’s the tool that you happen to have on hand. 

Or you can just skip pruning like many gardeners do and let the rhododendron take over the landscape. They sure are pretty when they grow big like that!

It's funny how you inherit the landscaping when you move into a new home and sometimes you end up loving something you would never have chosen, like my white weeping cherry tree and other times it becomes a headache because was done wrong, like the placement of the grape vines. Do you have any trees or bushes you inherited when you moved in?

Related reading: Want more information on organic gardening? Check out this collection of articles on gardening.

~L

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