Rhododendrons are real eye-catchers in every garden. But you have to be well informed about their requirements, so that they also bloom magnificently.
The rhododendron (Rhododendron) is a versatile plant that geographically covers a large area. Its flowers shine in many bright colors and delight the minds of many hobby gardeners. The deciduous, semi-evergreen or evergreen shrub from the heather family (Ericaceae) makes a great addition to any garden. We'll tell you how you can make rhododendrons at home in your garden and what you should bear in mind.
Rhododendron types and varieties
With over 1,000 species, the Rhododendron genus is one of the largest shrub genera worldwide. It is therefore not surprising that there are countless types and varieties for home and garden to buy. We have put together a small selection of the most popular types and varieties for you.
Rhododendron subgenus Azaleastrum
Tall shrub-like varieties (up to 5 m); flowering time between March and April; mainly white bloom; hardy to -12 °C
Rhododendron subgenus Hymenanthes
Growth habit Tree-like; rather unpopular in German gardens; partly hardy to -15 °C; flowering between January and May; mostly pink to bright red flowers
Rhododendron subgenus Therorhodia
Dwarf shrub species (between 30 and 40 cm); some species hardy to -30 °C; flowering time between May and June; partially bicolored flower (pink-purple; rarer white, pink or red)
Popular Rhododendron Varieties:
- 'Cunningham White'
Large-flowered hybrid; large white flower; relatively site tolerant; frequent finishing on INKARHO base; grows to over 2m tall - 'Nova Zembla'
Large-flowered rhododendron; robust and hardy; flowers in soft pink to strong red; Flowers have dark spot patterns - 'Bloombux'
Hybrid; evergreen variety; is offered as a boxwood alternative; very easy to care for and rich in flowers; Flowering in April/May
You can find more information about the 20 most beautiful rhododendron species and varieties here.
Buy Rhododendron
You can already do a lot wrong when buying your rhododendron specimen. The selection of the plant sometimes decides whether the cultivation of rhododendrons in your own garden will be successful or not. We'll walk you through some simple tips on how to choose the best plant for your garden.
Buy rhododendrons: watch out for pests and diseases
The rhododendron is predestined for attack by fungal diseases. Small yellow lesions and wilted leaves, for example, indicate the common leaf spot disease, but Phytophtara wilt is also a serious disease in rhododendrons. In addition, some animal pests cause problems for the rhododendron, including the rhododendron cicada. However, the cicada itself acts more as a vector for fungal diseases by creating entry points by laying eggs in the buds. So when you buy your rhododendron, make sure that the plant is free of lesions and small animals. If you buy from a professional, however, the probability of disease infestation is very low.
Buy Rhododendron: Examine the Roots
For more than twenty years, breeders have been working on being able to plant rhododendrons in neutral and slightly alkaline locations. By grafting a wide variety of varieties on a rootstock of lime-tolerant varieties, it has been possible to breed so-called INKARHO rhododendrons. These form a stronger root system and can therefore be planted on almost any soil. So when you buy it, look out for the label "INKARHO" so that you can enjoy lush flowers in your garden.
Tip: Even if you find slightly acidic soil in your own garden, INKARHO is an INKARHO variety a good choice. Due to its strong, extensive root system, faster and more vigorous growth can often be observed, which is also reflected in magnificent flowers.
We have put together all the information you need to buy the right rhododendron here for you.
Rhododendron: The right location
The rhododendron originally comes from higher regions. Special conditions prevail there, to today'sVarieties for the garden are still well adapted. We'll tell you the most important things about choosing the right place for your rhododendron in a nutshell.
The rhododendron tolerates direct sunlight well under certain conditions. If the soil is of the right quality and a continuous water supply is guaranteed, your darling can also withstand hot weather. However, during very long periods of heat associated with drought, the rhododendron prefers partial shade in the shelter of larger trees and shrubs.
The right soil for rhododendrons
The rhododendron is used to growing on shallow and rather acidic locations. These properties result from its origin in higher geographic locations. For the perfect location in the garden, this means: loosen the soil well and mix it with lots of humus. The humus slightly acidifies the soil and ensures good permeability and an optimal grain size spectrum. Since the shallow soils in mountainous areas are often very permeable, it makes sense to work a drainage layer of gravel into the planting hole. Find out more about the right soil for rhododendrons here.
Plant rhododendrons
The rhododendron is undoubtedly one of the most widely cultivated evergreen garden perennials. This actually suggests that its planting and care requirements are comparatively low. On the contrary: there are a few things to consider when planting rhododendrons. We explain step by step what is important:
1. Dig planting hole
The rhododendron is a sensitive flat-rooted plant that loves permeable and slightly acidic soil. Therefore, dig a spacious planting hole (about three times the diameter of the root ball) and enrich the soil with peat or special rhododendron soil (and coffee grounds if necessary) to acidify the soil. Furthermore, with heavier soils, a drainage layer of gravel should be laid at the bottom of the planting hole, or at least half of the filler soil should be replaced with sand. This increases the particle size spectrum and prevents waterlogging.
2. Planting rhododendrons
The rhododendron is usually sold in a pot with a well-developed root ball. Pull the plant out of the pot with the root ball and place it in the planting hole. Then fill the planting hole with the sand-hummus soil mixture,until 2 cm of the root ball protrudes from the ground and lightly press the loose substance. This will prevent the rhododendron from being planted too deep and possibly dying off the root system.
You can find more detailed instructions on planting a new rhododendron here.
Read our special article on how to properly transplant an older rhododendron.
Rhododendron in pot for balcony or terrace
Even if you don't have a large garden, it doesn't mean that you have to do without rhododendrons. Certain species such as Japanese azaleas and dwarf varieties such as Rhododendron 'Yakushima' are also suitable as a container plant and can decorate the balcony or terrace with their magnificent flowers. When choosing the pot for the rhododendron, the following should be considered: the shape of the pot should be wider than high to accommodate root development. Good water drainage should also be ensured. Several holes and a drainage layer are ideal so that the root is never wet and rot is prevented.
You should also think about hibernation in good time. Because even if the rhododendron variety is considered hardy, the cold must never act directly on the roots. And it should not be directly exposed to wind and sun during the winter. However, if you have considered these points, nothing will stand in the way of your rhododendron in the pot.
Caring for Rhododendrons
The Rhododendron genus is generally more at home in acidic locations. If these conditions are not given in your garden, it is advisable to give it a helping hand. We will tell you how you can easily create optimal conditions for your rhododendron. You can find everything about caring for rhododendrons here in our special article.
Watering rhododendrons
Rhododendrons are at home on very well drained and shallow soils. This makes them very sensitive to waterlogging. Young plants should still be watered regularly, preferably daily, but without over-saturating the soil.
Tip: Several small waterings a day are always the better solution if you are not sure how much to water.
Fertilize Rhododendron
In contrast to many other heather plants, the rhododendron is very hungry. That's why you shouldn't let your loved one go hungry eitherfertilize regularly. However, it is important to choose the right dose at the right time. Experts advise fertilizing young plants that were planted in spring with a long-term fertilizer. Special rhododendron fertilizers or generally applicable, primarily organic fertilizers with a long nutrient release are suitable for this. Many rhododendron experts swear by horn shavings as an additional source of nutrients. Between 20 and 30 grams of horn shavings per square meter are sufficient.
Tip: Our Plantura organic hydrangea fertilizer is a primarily organic organic fertilizer with a long-term effect and is therefore ideal for rhododendrons. The fertilizer releases its nutrients slowly and gently over a period of three months and provides your rhododendron with iron.
Older established plants are also fertilized at the same time as young rhododendrons planted in spring. A long-term fertilizer such as our Plantura organic hydrangea fertilizer is applied in March or April and then fertilized with horn shavings as required. However, the dose of horn shavings should not exceed 120 grams per square meter.
Tip: Anyone who likes to drink coffee and is also a rhododendron fan has found the perfect combination. Coffee grounds have proven to be an excellent fertilizer for rhododendrons because they are completely organic, provide a wide range of nutrients and also slightly acidify the soil. To remove the coffee grounds, simply work them into the surface so that they decompose as quickly as possible.
We have compiled more information about fertilizing rhododendrons for you in our expert article.
Pruning Rhododendron
The rhododendron impresses with its lush flowers and spreading branches. This opulent eye candy does not require regular pruning. However, in order to keep your pet in good shape over the long term, it should be trimmed at irregular intervals. We reveal how it works.
Rhododendron: when and how to cut?
The right time to cut always depends on the reason for the cut. If you would like to carry out maintenance pruning to keep your rhododendron in shape, it is best to do this after flowering, between May and June. However, if a more radical pruning is required because the rhododendron is becoming increasingly bare on the inside, this should be done in autumn or spring. When pruning rhododendrons, proceed between twocases can be distinguished. On the one hand there is a radical rejuvenation pruning, on the other hand you can keep your rhododendron in shape with a maintenance pruning. We explain what you need to look out for.
Pruning rhododendrons: maintenance pruning procedure
In order to keep your rhododendron in shape, it is advisable to carry out a more reserved maintenance or topiary cut. A good time to do this is right after flowering. Here you can estimate the later shape of the bush, remove some of the withered flowers and not damage the bush too much, so that its photosynthesis performance is not restricted and enough energy can be provided for the coming flower.
How to proceed: Simply cut the shoots a few centimeters below the tip of the shoot with sharp rose scissors so that you are satisfied with the visual cross-section. Note: The pruning also promotes branching and ensures denser foliage and flowers in the following year.
Rhododendron Pruning: Taper Pruning Procedure
The cold winter months, when the rhododendrons remain dormant, are the right time for a comprehensive pruning. To do this, use sharp rose scissors to cut back old shoots, exposing the inner parts of the bush again so that light can flow in.
The following applies to pruning after flowering: remove diseased and dry shoots, but leave shoots with buds intact. With both types of cut, always cut the shoots at an angle so that dew and rainwater can run off.
You can find more detailed instructions on how to cut the rhododendron here.
Note: We always recommend wearing gloves when working on rhododendrons as the shrub is poisonous. For more information on the poisonous rhododendron, click here.
Rhododendron: Common Pests and Diseases
The rhododendron is often attacked by fungal diseases, but insects also affect the popular garden shrubs. We provide a brief overview of the most important diseases and pests affecting rhododendrons.
Rhododendron Cicada
- Small light green species
- Caused by oviposition Portal of entry for fungal infestation; brown flower buds are the result, covered with fungal growth in springbecome
- Control of the cicada through preventive measures: Good location, proper care and needs-based fertilization
- Use of chemical pesticides possible, but only against vectors (cicada), not against fungi
- Fighting the fungus transmitted by cicada by removing the dried up buds
Once weevil
- Big Black Beetle
- Feeds at night on leaves of rhododendrons and other evergreen plants
- Damage from leaf edge feeding
- Both beetles and larvae dangerous; Larvae feed on roots
- Fighting by laying out old, rotten boards that serve as protection for the beetle; Beetles can then be collected
- Nematodes effective as beneficial; chemical crop protection virtually hopeless
Leaf spot disease
- Common; easy to identify
- No clear picture of damage, as many weakening parasites can be triggers
- Brown lesions in leaf center and leaf margin typical; partial curling of leaves
- Control exclusively through preventive measures (location and care) and chemical preparations
Powdery mildew
- Infestation with powdery mildew manifests itself as white mycelium on the upper side of the leaves
- Frequent problems with powdery mildew from mid-July
- Knap Hill Azaleas particularly affected
- Powdery mildew does not directly cause the leaves to die off, but it can weaken the rhododendron through prolonged infestation
- Control by preventive measures before infestation and chemical preparations after the first signs of infestation; Use of chemical agents more effective the earlier the infestation stage
You can find more information about common diseases and pests of rhododendrons and how to combat them here.