Rhododendrons: amazing beauty of the blossoms in the home garden
Maie Vridolin, Maie’s Garden
Rhododendrons are beautiful and peculiar ornamental plants. The first rhododendrons were planted in gardens in England at the beginning of the 19th century, so the experience in growing these plants is nothing really when compared to roses, for example.
In our garden at Paikuse (Maie’s Garden), there are 26 rhododendron types and varieties. There are larger and smaller varieties, deciduous and evergreen ones. They are all very beautiful and if the right soil and growing site are found and the types and varieties suitable for our climate chosen, they are easy to grow and care for.
What is a suitable growing site for a rhododendron?
To grow, a rhododendron needs coarse peat and sand mix soil that is acidic enough (pH level 4.5–5.5). It enjoys a light and superficial peat layer. Peat makes for a nice and fluffy growing site for the plants. For our rhodos, we brought fallen-down needs, pieces of branches and bark and oak leaves from the forest. In forest mould, there is a lot of mycelium, which helps the acidophilic plants better obtain the nutrients from the soil.
Rhododendrons like to grow in a thinner pine grove or any other site that provides some shade in the winter. In sunlight, rhodos do indeed develop more flower buds than in shade, but due to the peculiarity of our climate, we should still find a half-shaded growing site for rhodos to avoid the early spring sunburn.
A rhododendron bed in the home garden
The natural conditions perfect for rhododendrons are present in not very many gardens, but if you know the growth requirements, you can create a good site practically anywhere. What to consider when creating a rhododendron bed: should you create the planting area in a trench filled with the required substrate, or create a raised bed? A raised bed justifies itself on clayey soils because rhodos enjoy stable humidity and are afraid of excess water. On clayey surfaces, crushed granite or light gravel drainage (do not use crushed limestone) should be established in addition to the raised bed. The rhododendron bed in our garden has been created in a trench because we mostly have sandy soil here. The soil dug out can be used to build raised planting areas in the garden. We did not cover the base of the rhododendron garden with an insulation cloth because we have no aggressive weeds and limestone in the soil which would easily neutralise the peat’s acidity. We have created our rhododendron bed under a large mountain pine. However, be careful when creating a rhododendron bed near large trees. Pine, oak and other ancient trees with deep roots are a good choice because their roots will not compete with those of the rhododendron.
Which rhododendron types and varieties should be preferred?
Most of the rhodos sold here are hybrids grafted on cold-hardy understock, which manage well in our climate. It would be smart to choose hybrids developed in Canada, Sweden, Latvia or Finland. In our garden, almost all of the rhodos originate from the Baltezers Tree Nursery, which is well known among Estonian garden enthusiasts. According to the well-known rhododendron grower Mihkel Saar, the disadvantages of the Finnish varieties are thin bush shape and pale colour of the petals, and advantages are speedy growth and good resistance to winters.
Fertilising and watering rhododendrons
Once you have selected a good type, variety and growing site, rhododendrons do not really need much care. However, there are a few things to consider. For example, during and immediately after blooming, rhodos need water the most because of their active growth period following blooming when the plant is producing new shoots. Of course, watering extends the beautiful blooming time as well. Acidic rain or bog water is good for watering. If you don’t have any, use stale pond water to pamper the plants, or soften regular water by soaking peat in it. Apple cider vinegar can also be added to water (1 tblsp per bucketful of water).
With their rich blooming period, rhododendrons lose a lot of energy, so they should definitely be fertilised in May–June. I usually fertilise mine once in May with special fertiliser for acidophilic plants. I mix it with a substrate and water the plants during a dry period to help them better obtain the nutrients. Finish fertilising before Midsummer Day; any fertilising later than that may cause secondary growth of the plant and it will not have time to lignify for the autumn. In addition to fertilising, I have added fresh peat to the bed so that the substrate would always have the soil reaction rhodos need.
When should you cut and transplant it?
It is advised to break off the flowerheads of rhododendrons after blooming, so the plant can use this energy otherwise used for seeds to ripen for the development of flower buds instead. Of course, the bushes will look aesthetically better as well.
Our rhodo garden is twelve years old already and I don’t break the flowerheads off anymore. First, it takes a lot of time because our rhodos are rather large and tall; I also hope that when growing the seeds, they do not have the energy left to send out very long new growth and will be more compact. I definitely recommend breaking off the flowerheads on young plants.
Rhodos put up with transplanting very well. It should be kept in mind that the roots go about 30 cm deep only and spread out. So the root ball should be dug out with plenty of soil around it. Also, rhododendrons tolerate cutting well, even though this is not really done much. If your plant is too wide or too high, cut it into a shape. June is the right time to do this. The plants respond well to pruning; after blooming, cut a young shoot so that one young leaf is left. All shoots may not be pruned every year because after cutting, no flowers will grow on the shoot next year. In the lower part of a rhododendron shoot, there are the “dormant” buds, and the bush can be renewed by cutting it back. This can be done when the bush has suffered a lot of damage for any reason (strong sunburn, for example).
Covering up the rhododendrons
If there is a risk of too much sun on the rhodos in the winter, they need to be covered up. The shade cloth should not be spread right across the plants, but support pegs should be used and placed in the form of a pyramid above the plant. This will avoid the branches breaking under the weight of the snow because the snow will not remain on the cloth. It is smart to put the support pegs and the shade cloth in place in the autumn already to avoid missing the first sunny days at the end of January and the beginning of February when the sun is powerful enough to damage the plant even though the ground surface is frozen. Do not use insulation cloth or a shade cloth designed to mainly keep the warmth in. Using these, water starts evaporating from the evergreen rhododendron, the leaf will dry up and turn brown, and the plant may die.
There are differing opinions on mulching a rhododendron garden. Excessive mulch prevents the peat from melting in the spring and there is a risk of sunburn. Instead of mulching the peat garden, I have covered the free space with acidophilic shade plants. Even some mosses have started growing under the rhodos, and I have found some mushrooms as well.
Diseases and pests on rhododendrons
Rhododendrons are part of the plant group that is not much damaged by diseases and pests. Over the past few years, a dangerous fungal disease has started spreading on rhodos – sudden oak death – which has been brought into Estonia with imported plants. We can avoid diseases and pests if we guarantee optimum growing conditions for the rhododendrons because a weak plant is more likely to be hit harder by the disease.
The delightful deciduous rhododendrons
In addition to the evergreen rhododendrons, we have deciduous ones in our garden as well. The deciduous rhododendron types which, as a rule, are more resilient than other types and which we have brought from Tõnu Lind in Häädemeeste, are a truly beautiful sight of blossoms to enjoy.
Deciduous rhododendrons do not need a lot of maintenance because they lose their leaves in the autumn and are not in danger of sunburn in the winter. Also, they are more cold-hardy than evergreen rhodos and less prone to diseases. They look very nice in the autumn when the leaves change into autumn colours before falling down. A gardener only starting out should definitely try out deciduous rhododendrons.
We enjoy our rhodo bed a lot. Over the years, a luscious and rich flora has developed around the large mountain pine, and we lovingly refer to it as “our forest”. In our garden, we have planted lots of perennials, heathers, bulbous flowers and grasses in between the rhodos, there are plenty of flowers and different leaf structures to enjoy throughout the growing time. Each year at the beginning of the summer, during peak bloom time, we open our gates for free visits. You can find information about the events in our garden on the Facebook page of Maie’s Garden (Maie Aed).