Spring is a wonderful time in the garden and one of the highlights is the blooming of those queens of the woods, the large group of flowering shrubs called rhododendrons, or ‘rhodos’ as many gardeners often call them. They all have clusters of gorgeous bell-shaped flowers in all the colors of the rainbow, a wide range of sizes and an ability to thrive in shady sites where other plants fade away. These versatile plants are key components of any garden scheme that aims to make an ordinary garden into a thing of beauty. Some people think that these plants are hard to grow and it is true they do have some special requirements, especially for soil, but if you have conditions that are basically suitable you can grow these beautiful plants with just some simple care that will be rewarded many times over by their stunning display.
Using Rhododendrons on your property
Shade is the biggest ‘problem’ in many gardens, especially if you have mature shade trees like maple on your property. Instead of struggling to grow unsuitable plants it is best to concentrate instead on shrubs that naturally grow and thrive in shade. Rhododendrons are at the top of that list. Beautiful spring gardens, small or large, can be created beneath trees by planting these shrubs, along with other shade-tolerant plants like Camellias, Hollies, Yew and Canadian Hemlock, in beds between the trees. Don’t try to plant right against the trunk, because there will be a lot of roots, but make beds in the areas between the trees instead.
These beautiful plants can also be grown in mixed sun and shade positions alongside many other flowering shrubs as foundation planting around your home. As well as flowering spectacularly in spring, they all have good foliage with attractive green leaves, usually evergreen, so they look good all-year-round and give great structure to your plantings.
Rhododendrons, especially the smaller kinds, are also great in containers and planter boxes. This is an excellent way to grow them if your garden soil is too alkaline to allow you to grow them right in the garden, so whatever your soil is like, you can still enjoy these fantastic plants.
What are Rhododendrons like?
There are literally thousands of different Rhododendrons to choose from and they vary greatly in height, hardiness, flower size and flower color. They are all shrubs with multiple stems coming from the ground and can be anything between one and 20 feet tall, although most garden varieties are in the two to six foot range. They are often as broad as or broader than they are tall. The leaves are always simple ovals in shape, with smooth edges, but they may be anything from an inch to eight inches or more in length. Flowers are carried in trusses of 6 to 20 blooms, on the ends of the branches, often completely smothering the plant. They are funnel or bell-shaped, sometimes with extra circles of petals making a gorgeous show. Pinks, reds and lilacs are the most common colors, but yellow, purple and of course white are also found in these varied plants.
They all flower in spring, anytime from the melting of snow to the end of spring and some will produce another crop of blooms in late summer or early fall.
There are Different Kinds of Rhododendrons
We can break these plants up into three main groups:
First there are the Azaleas. These are smaller plants, with small leaves and showy flowers. They are usually evergreen but some may be deciduous. There are many kinds but the gardening world has been taken by storm in the last few years by the Encore Azaleas, which bloom not only in spring but also in late summer. There are a host of colors available, from white to deep red. These beauties are hardy from the warmer parts of zone 7 into zone 10, so they are a great plant for gardeners in the warmer parts of the country.
Secondly are the small-leaved rhododendrons. These are often very hardy and so they are great choices for gardeners in colder regions. Most are hardy to zone 5 and often to zone 4 and one, the Hellikki Rhododendron, is hardy into warmer parts of zone 3. It was bred in Finland especially for cold climates and its dark violet-red flowers on four foot tall plants make a great show in the coldest parts of the country. Other hardy plants of this type include the April Rose Rhododendron, which will thrive in zone 5. For something different, grow the Lemon Dream Rhododendron, which stays under three feet tall and has soft lemon to white blossoms.
Thirdly we have the large-leaved rhododendrons. These, as the name suggests, have leaves that can be eight inches long, or even more and they usually have large flower-trusses to match. Some are bred from our own American species, the Lavender Rhododendron. The most outstanding of these is the Nova Zembla Rhododendron, which has enormous trusses of rich-red flowers and large leaves on an elegant shrub with grey bark that can reach 10 feet tall or more in time. This beauty is also special because it is the most sun-tolerant of all the rhododendrons – in fact it performs best in sunny locations, where it will be completely smothered in blooms. It is one of the few rhododendrons suitable for a lawn specimen.
Most of this group are really only hardy in zones 6 or 5, but the English Rose Rhododendron is hardy into zone 4, and with its classic lavender-rose flowers it makes a lovely display.
Planting and initial care
If you are considering growing rhododendrons, the first step is to test your soil for its acid/alkaline balance. If your neighbours are growing these plants successfully you can assume they will grow for you, but otherwise a soil-test kit can be found cheaply at any garden centre or hardware store. It just takes a few minutes to test your soil and if it is less than 5.5 on the pH scale, you are set to go as a rhodo grower. If your soil is pH7 or less you can still grow these plants, but it is a good idea to get some chelated iron and apply it every spring before new growth begins. No matter what your soil, if your plants have yellow new leaves or leaves that are light-green with darker-green veins, use chelated iron on them.
If your soil is more than pH7 you may still succeed, especially with the Lavender Rhododendron or with the Nova Zembla Rhododendron if you use the chelated iron once or twice a year and if they do well then you could try some others as well. However with their fine root-systems rhododendrons do well in planters, so pick up some potting soil for acid-loving plants and some of the same kind of fertilizer too and you can have a beautiful rhododendron season no matter what your soil is.
The less acid your soil, the more important soil preparation will be for these plants. Digging plenty of peat-moss into the planting area is the first step. Well-rotted leaves are also a good soil addition. After you plant mulch the area with a layer of peat or leaves two or three inches thick and renew the mulch annually in early spring.
When planting, dig a hole that is three times the width of the pot and just a little deeper and plant at the same depth as your plant was in the pot. Rhododendrons should not be planted deeply at all. Use plenty of water during planting – a good trick is to only put back part of the soil, flood the hole with water and put the rest of the soil back when it has all drained away. The lower levels of the soil will now be nice and moist.
The other essential for Rhododendrons is water. They like soil that is damp, but they do not like wet, boggy conditions. Especially when newly-planted, make sure that your plants never become dry, but even mature plants will suffer during droughts, so water well every few days. In pots let the soil dry just a little before watering thoroughly.
Spring fertilizer is a good idea – us a mix especially designed for rhododendrons, which will be available at any garden centre.
Pruning is normally not needed and is often a bad idea, so let your plants develop naturally. To encourage the maximum flowering, carefully remove the old flower trusses as soon as the last blossoms have fallen. Do this by snapping them off gently with your fingers right at the bottom of the truss – don’t remove any leaves. This is a better and quicker method than using pruners once you get the hang of it. Doing this will ensure that your plants put all their energy into flowers for the following year instead of into seed-making.
Rhododendrons are a wonderful plant for any shady garden and should be planted in profusion so that you can enjoy the spectacular and unique display they bring each spring. Nothing else can compete with it and these plants mature and develop over the years to become better and better with every passing season. With such a wide range of colors, sizes and hardiness there is a rhododendron for everyone, everywhere. They make any garden a special place, so start your collection today.