There’s a reason why rhododendrons are so popular. And it’s very obvious. They are just so colourful. Is there another plant that makes such a bold statement of colour? And, with so many different colours and shades, as well as sizes and leaf shapes, it’s little wonder that rhododendrons are such a popular plant. 

I’m sure many of us will have a rhododendron or two in our garden but, if you’re new to growing these most colourful of plants, or just want to give yours a little boost, here’s our top tips on getting the most from your rhododendron shrubs.

1 The right time to plant 

There are a few things to keep in mind when choosing when to plant your rhododendrons but the most important is that you must wait until well after the first frost. Planting them once spring is well established is the best bet. 

That said, if you are planting your rhododendrons in a container then you can typically plant them at any time of the year. Although sometime between October and April will likely yield the best results. Planting after this does have one advantage in that you can purchase ready-bloomed plants so you get a good idea of the quality.

2 Finding the right spot

As well as knowing the right time to plant your rhododendrons, you need to find the perfect spot. The problem is that these plants can be quite choosy and if you don’t get the location just right, they won’t do very well. 

If you have a large leaf rhododendron then you will need to find somewhere that receives just a couple of hours of morning sun with the rest of the day in shade. However, you don’t want to place them where it’ll be too shady as this can cause problems too. Always keep them out of the afternoon sun.

3 You need the right soil to grow rhododendrons

Rhododendrons like acidic soil and preferably one that is humus rich. It’s also better to have a well-draining soil but you will need to keep it moist. If your soil isn’t acidic the best way to make sure that your rhododendrons have everything they need is to grow them in a container as opposed to trying to alter the ground soil which can be tricky.

Subscribe to our newsletter for exclusive offers and discounts

While the soil should be moist, rhododendrons do not like having wet roots so if the ground is overly wet, this will likely result in your plants dying. Clay soils can be particularly difficult to work with so make sure you plant the rhododendrons in a mound of altered soil for the best results. 

4 How to plant rhododendrons

When it comes to planting rhododendrons, you will need to dig a hole that is twice the width of the root ball and just as deep. The key is to plant the bush at the same level it was planted in the container it came in so that the roots are just below the surface of the soil.

When you’re ready, take the plant out of the container and gently tease the roots if they have circled around the pot. This ensures good root spread once the plant is in the soil. Before you put it in the ground, be sure to soak the root ball in some water until no more air bubbles come out.

5 Give them the right amount of space

If you want your rhododendrons to really thrive, you need to make sure that they have a good amount of space. You can plant them in groups if you want to create a colour block but these groups should contain no more than three to five bushes.

Before planting, make sure you are aware of how high and wide the rhododendrons will grow as this will give you a good idea of how much space you will need to leave between each one. That said, it is possible to plant them a little closer if you want dense foliage. As an example, a bush that will spread two and a half metres could be planted just two metres from its neighbour.

6 Using mulch for rhododendrons

Mulch is an excellent way of providing natural nutrients to your plants and when you are growing rhododendrons, it’s essential. You will need to add a layer of two to five inches of mulch during the spring. This much should be made from pine needles as this will help the soil to retain its moisture.

Some people make the mistake of creating a mulch volcano around the trunk of the rhododendron bush but this is not a good idea. It will create far too much moisture and can lead to root rot so make sure you leave some mulch free space around the base of the trunk.

7 Watering rhododendrons

In the wild, rhododendrons grow in areas where there is a lot of rain so they do like the soil to remain as moist as possible while still being well draining. They are ideal for borders as because their roots are shallow, they won’t be in competition with deeper rooted plants nearby.

In general, you will need to only water your rhododendrons if there has been less than an inch of rain that week. However, tap water in hard water areas can contain too much calcium which is bad for the rhododendrons. If possible, try collecting rainwater and using this instead.

8 Fertilising rhododendrons

There is really no need to go over the top when it comes to feeding your rhododendron bushes. If you give them too much fertiliser, this will burn the roots and could kill the plant entirely. Any bone meal containing products should also be avoided since there is far too much calcium in this.

Instead, we would suggest using a slow-release fertiliser and only do this one at the beginning of spring. Make sure to follow the pack instructions to the letter but for rhododendrons, you generally won’t need more than 70g for every square metre of soil.

9 Pruning your plants

Rhododendrons flower during the spring and as a general rule, you shouldn’t prune shrubs like this at all. However, you may wish to control the height and spread of your rhododendrons and that’s OK as long as you wait until after they have finished flowering.

It is also OK to remove diseased or dead branches and you can do this at any time of the year; don’t worry about waiting for the blooming period to be over. When removing stems, just snap them off by bending them, being careful not to interfere with any buds at the base.

10 Caring for rhododendrons in winter

Since the roots of your rhododendrons are only just below the surface of the soil, they can be prone to problems from the cold during winter. The best way to protect them is by adding lots of organic mulch around the base of the bush before the cold sets in.

With evergreen species, you can wrap the plant with burlap or a horticultural fleece. If you don’t protect them then there is a serious risk of them withering and ultimately dying. It’s also essential to make sure that you provide your rhododendrons with plenty of water throughout winter if there is not a lot of rainfall; just be sure not to water on very cold days.

Check out our range of rhododendrons and other flowering shrubs. All are grown by us in our Norfolk nursery and will be carefully packed to ensure they arrive at your door in the very best of health.