The Tree Center

Free shipping over $149 30 Day Guarantee Delivered to your door

How to Grow Perfect Rhododendrons and Azaleas

June 29, 2020

Written by Dave G.

Almostall gardeners agree that there is nothing so beautiful as a garden with rhododendrons and azaleas growing in it. But often the first attempts are disappointing, and these plants are often relegated to an elite category, only for those who have the mythical ‘green thumb’. This is a shame, because with some care when choosing and planting, and the right after-care, they are not difficult at all, and you too can enjoy that special joy that comes from seeing these magnificent flowers thriving and blooming in your own garden.

5 Tips That Will Give You Perfect Rhododendrons and azaleas

What’s the difference between Rhododendrons and Azaleas?

Although we separate them, in reality these are the same group of plants, and azaleas are nothing more than a group of rhododendrons that have small leaves, often covered with fine hairs, instead of the large, leathery leaves of most other members of this plant group. Although in most gardens these are the two types that are seen, this very large plant group, with other species and thousands of garden varieties, includes deciduous shrubs too, and tropical semi-climbing plants as well. This ‘rhodo/azalea’ split is just a gardener’s convenient language for different looking plants, and it has no firm meaning.

Check your Zone

There is nothing more frustrating than trying to grow a plant in places that are too cold or hot for it. Fortunately, there are Rhododendrons that are suitable for almost every zone in America, so there is always going to be something for your garden. Save yourself anguish and choose varieties recommended for your zone. In colder areas, start with the P.J.M. varieties, which are certainly the most reliable in zone 4, and once you are having success with them, move on to other things.

Check your Soil

A big reason for the success of this group of plants in growing all around the world, is their ability to grow in acidic soils. Many other plants can’t, but these soils are found on many continents, so that ability means they meet less competition for space to grow in. But evolving that ability made it impossible for them to grow in anything that isn’t acidic, and we have to allow for that.

It is easy to check your soil pH with a probe, or a simple kit from a hardware or garden center. Even easier is to see what your neighbors are growing. Although not 100% reliable – they or you could be sitting on a pocket of soil that you don’t share – it’s a pretty good guide. If you have established gardening neighbors, and they have azaleas, rhododendrons or camellias growing well in their gardens, the chances are good that you can grow them too. Much of the east of North America has naturally acidic soil, so you could easily be lucky. . .

The soil for these plants needs to have a pH value less than 6.0, and as low as 4.5. If this means nothing to you, take a look at this older blog with more details. If you are between 6.0 and 6.9, you might be successful, but there have been more wasted words written about making your soil acidic than on any other topic. Despite all the earnest instructions, this is almost impossible to do – unlike making your soil more alkaline, which is dead easy. You might be able to nudge it one or two tenths of a unit for a few years, but that is unlikely to turn an ‘unsuitable’ soil into a ‘suitable’ one, although if you already have acid soil it may give you some improved growth.

Before you give up, there is a solution, and that is to grow these plants in pots. They have fibrous root systems, and they will thrive for years in planters and tubs, with a little care. Plant them in blended potting soils designed for acid-loving plants, and you will soon have some beautiful specimens for your terrace, or to stand out in your garden beds. If you enjoy more ambitious garden projects, you can build a raised bed, at least 12 inches deep, filled with a suitable soil mix, Be aware, though, that alkalinity from the soil beneath will rise up into the new earth after a few years, so it is not a long-term solution.

Get the Light Right

The best blooming will happen on plants that have good light levels. The ideal would be morning sun and afternoon shade, and that shade is especially important in hotter zones. The other ideal situation for your rhododendrons and azaleas is in the dappled shade beneath tall deciduous trees, especially those that don’t throw a heavy shade. Trees like Norway maple, for example, make a very dark shade, will birch, oak, and most other maples throw a lighter, more suitable shade. If you have a semi-natural piece of woodland, removing most of the smaller saplings will let more light in. The shade beneath most evergreens is too ‘year-round’ and dense for your plants to do well.

Maintain Even Moisture Levels

Besides being acidic, good soil for these shrubs is moist, but not wet and boggy. Adding lots of organic materials (check that they are lime-free) will improve the moisture retention and allow better water flow, at the same time as improving drainage and letting more healthy oxygen into the soil. Regular mulch helps retain moisture too, and feeds your plants as well.

Remove Spent Flower Clusters

This is the ‘green thumb’ secret to doing well with all types of rhododendrons and azaleas. If your plants are not too large, take a few minutes to remove the flower clusters once they have finished blooming. The quickest and best way is to snap them off briskly, just above the first pair of leaves. Look closely and you will see the new buds or shoots of the stems that will grow and mature over summer and fall, preparing flower buds for the next spring. Removing those flower stems means your plants put their effort into making next year’s blooms, and don’t waste it making seeds. It also keeps your bushes looking neater. Don’t make the mistake of trimming your plants in summer – in fact it is best not to prune at all, at least with young plants. Any trimming in summer will usually mean no flowers on the stem you cut.

Use Suitable Fertilizers

Check with those who have the best gardens, and it is almost certain they use fertilizer of one sort or another, from rich compost and manures to more concentrated organic or chemical fertilizers. There are lots of suitable blends for acid-loving plants, and they all help give you good results. Check that they provide iron, which is always important for these plants. Regular feeding, at the right times of year – especially just after flowering – is most important for plants in pots. Using something is more important than exactly what you use.

 

These tips and techniques will give you a wonderful spring display, plus summer and fall too if you grow some of the amazing re-blooming azaleas we stock – check them out.

 

***If you want to check the availability of any of the plants mentioned here, go to our Home Page, click on the ‘Search’ button in the upper right, and type in your choice – both common names and botanical ones will work. If, sadly, you find the item sold out, click on the ‘notify me’ box beside the size you want, and you will get an email the moment that plant is available again – it’s easy.