Rhododendron: plants, in pots & care

Rhododendrons are real eye-catchers in every garden. But you have to be well informed about their needs in order for them to bloom splendidly.

The rhododendron (rhododendron) is a versatile plant that geographically extends over a large area. Its flowers shine in many strong colors and delight the minds of many hobby gardeners. The deciduous, semi-evergreen or evergreen shrub from the heather family (Ericaceae) is a great addition to any garden. We'll tell you how you can make the rhododendron at home in your garden and what you should pay attention to.

Species and varieties of rhododendrons

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

Shrub-like varieties with high growth (up to 5 m); Flowering period between March and April; mainly white flower; hardy to -12 ° C

Rhododendron subgenus Hymenanthes

Tree-like growth habit; rather unpopular in German gardens; partly hardy to -15 ° C; Flowering between January and May; mostly pink to bright red flowers

Rhododendron subgenus Therorhodes

Dwarf shrub (between 30 and 40 cm); some species hardy to -30 ° C; Flowering time between May and June; partially two-colored flower (pink-violet; rarer white, pink or red)

Popular rhododendron varieties:

• 'Cunningham White'
  Large-flowered hybrid; large white flower; relatively location tolerant; frequent finishing on INKARHO underlay; becomes over 2 m high
• 'Nova Zembla'
  Large-flowered rhododendron; robust and hardy; blooms in soft pink to deep red; Flowers have dark speckled patterns
• 'Bloombux'
  Hybrid; evergreen variety; is offered as an alternative to boxwood; very easy to care for and rich in flowers; Flowering in April / May

More information about the 20 most beautiful rhododendron species and varieties You will find here.

Buy rhododendrons

You can go wrong with the purchase of your rhododendron specimen. When choosing the plant, it is often decided whether or not to grow rhododendrons in your own garden. We'll explain to you with a few simple tips how to choose the best plant for your garden.

Buy rhododendrons: watch out for pests and diseases

The rhododendron is predestined to be attacked by fungal diseases. Small yellow lesions and withered leaves indicate, for example, the common leaf spot disease, but Phytophthara wilt is also a serious disease in the rhododendron. In addition, some animal pests cause problems for the rhododendron, including the rhododendron cicada. The cicada itself acts more as a vector for fungal diseases by creating entry gates by laying eggs in the buds. So when buying your rhododendron, make sure that the plant is free of lesions and small animals. However, if you buy from a professional, the likelihood of disease infestation is very low.

Buy rhododendrons: examine the roots

For more than twenty years, breeders have been working to be able to plant the rhododendron in neutral and slightly alkaline locations. By refining a wide variety of varieties on a base of lime-tolerant varieties, we have succeeded in breeding so-called INKARHO rhododendrons. These form a stronger root system and can thus be planted on almost any soil. When buying, look out for the name “INKARHO” so that you can look forward to lush flowers in your garden.
Tip: Even if you find slightly acidic soils in your own garden, an INKARHO variety is a good choice. Due to their strong, extensive roots, faster and more vigorous growth can often be observed, which is also reflected in a splendid bloom.

All information about the Buying the Right Rhododendron we have put it together for you here.

Rhododendron: the right location

The rhododendron originally comes from higher regions. There are special conditions to which today's varieties for the garden are still well adapted. We'll briefly tell you the most important things about choosing the right place for your rhododendron.

The rhododendron can tolerate 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 areas. In very protracted hot spells associated with drought, however, the rhododendron prefers partial shade in the protection of larger trees and bushes.

The right soil for rhododendrons

The rhododendron is used to growing in shallow and more acidic locations. These properties result from its origin in higher geographic locations. For the perfect location in the garden, this means: loosen up the soil well and mix it with plenty of humus. The humus slightly acidifies the soil and ensures good permeability and an optimal range of grain sizes. Since the shallow soils in mountain areas are often very permeable, it is advisable to work a drainage layer made of gravel into the planting hole. Here you can find out more about the right soil for rhododendrons.

Plant rhododendrons

The rhododendron is undoubtedly one of the most cultivated evergreen garden shrubs. This actually suggests that its planting and maintenance requirements are comparatively low. But on the contrary: There are a few things to watch out for with rhododendron plants. We explain step by step what is important:

1. Dig the planting hole

The rhododendron is a sensitive shallow root that loves well drained and slightly acidic soils. So dig out a large planting hole (about three times the diameter of the root ball) and enrich the soil with peat or special rhododendron soil (and if necessary with coffee grounds) to the soil acidify. Furthermore, with heavier soils, a drainage layer made of gravel should be laid on the bottom of the planting hole, or at least half of the filler soil should be replaced with sand. This increases the range of grain sizes and prevents waterlogging.

2. Plant rhododendrons

The rhododendron is usually sold in a pot with a well-developed root ball. Pull the plant and its root ball out of the pot and place it in the planting hole. Then fill the planting hole with the sand-humus-soil mixture until 2 cm of the root ball protrudes from the earth and gently press the loose substance. This will prevent the rhododendron from being planted too deep and possibly the root system from dying off.

A more detailed guide to the Planting a new rhododendron You will find here.

Like you already have Transplant older rhododendrons properly, read in our special article.

Rhododendron in a pot for balcony or terrace

Even if you don't have a large garden, that doesn't mean 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 be used on the balcony or terrace with their blossoming flowers decorate. When choosing the pot for the rhododendron, the following should be considered: The shape of the vessel should be wider rather than high in order to accommodate the development of the roots. Good water drainage should also be ensured. Several holes and a drainage layer are ideal so that the root is never in the wet and rot is prevented.

You should also think about wintering in good time. Because even if the rhododendron variety is considered hardy, the cold must never have a direct effect on the roots. And it should not be directly exposed to wind and sun during winter. However, if you have considered these points, nothing stands in the way of your rhododendron in the pot.

Maintaining rhododendrons

The genus of rhododendrons is generally more at home in acidic locations. If these conditions do not exist in your garden, it is advisable to help a little. We'll tell you how you can easily create optimal conditions for your rhododendron. Everything about the Care of the rhododendron can be found here in our special article.

Pour the rhododendron

Rhododendrons are at home on very well drained and shallow soils. This also makes them very sensitive to waterlogging. Young plants should still be watered regularly, preferably daily, but without saturating the soil too much.

Tip: Several small waterings a day are always the better solution if you are not sure how much to water.

Fertilize rhododendrons 

In contrast to many other heather plants, the rhododendron is very hungry. Therefore, you shouldn't let your darling go hungry and fertilize 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 slow release fertilizer. Special rhododendron fertilizers or generally applicable, mainly 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 completely sufficient.

tip: Our Plantura Organic hydrangea fertilizer is a primarily organic bio-fertilizer with a long-term effect and therefore ideally suited for the rhododendron. The fertilizer releases its nutrients slowly and gently over a period of three months and supplies your rhododendron with iron.

Older established plants are also fertilized at the same time as the young rhododendrons planted in spring. A long-term fertilizer like our Plantura is used in March or April Organic hydrangea fertilizer applied and re-fertilized with horn shavings as required. However, the dose of horn chips 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 dispense the coffee grounds, simply work them into the surface so that they break down as quickly as possible.

More information about the Fertilizing rhododendrons we have compiled for you in our expert article.

Cut rhododendron

The rhododendron impresses with its lush flowering and spreading branches. This opulent eye candy does not need a regular cut. However, in order to keep your darling in good shape in the long term, a cut should be made at irregular intervals. We reveal how it works.

Rhododendron: when and how to cut?

The right time to cut is always based on the reason for the cut. If you would like to carry out a maintenance cut to keep your rhododendron in shape, it is best to do so after flowering, between May and June. However, if a more radical pruning is required, because the rhododendron is increasingly bald inside, this should be done in the autumn to spring. When pruning rhododendrons, a distinction must be made between two cases when proceeding. On the one hand there is a radical taper cut, on the other hand you can keep your rhododendron in shape with a maintenance cut. We explain what to look out for.

Cutting rhododendrons: procedure for maintenance cutting

In order to keep your rhododendron shapely, it is advisable to carry out a more restrained conservation or shape cut. A suitable time for this is right after flowering. Here you can assess the future shape of the shrub well, remove some of the withered flowers and damage the shrub not too much, so that its photosynthetic capacity is not restricted and enough energy is provided for the coming bloom can.

How to proceed: Use sharp rose shears to simply cut the shoots a few centimeters below the tip of the shoot so that you are satisfied with the optical cut. Note: The cut also promotes branching and ensures a denser leaf and flower pattern in the following year.

Cutting rhododendrons: Procedure for tapering cut

In the cold winter months, when the rhododendron remains in hibernation, is the right time for a comprehensive rejuvenation cut. To do this, cut back old shoots with sharp rose shears and expose the inner parts of the bush so that light can flow into it.

The following applies to the maintenance pruning after flowering: remove diseased and dry shoots, but leave the shoots with buds standing. With both types of pruning, always cut the shoots at an angle so that dew and rainwater can drain away.

A more detailed guide to the Cutting the rhododendron You will find here.

Note: We always recommend wearing gloves when working on the rhododendron, as the shrub is poisonous. More information about the poisonous rhododendron get here.

Rhododendron: Common pests and diseases

The rhododendron is often attacked by fungal diseases, but insects do not stop at the popular garden shrubs either. We give a brief overview of the most important diseases and pests of the rhododendron.

• Small light green kind
• Entrance gate for fungal attack caused by oviposition; The result is brown flower buds, which are covered with fungal turf in spring
• Fight the cicada through preventive measures: Good location, proper care and fertilization based on needs
• Use of chemical pesticides is possible, but only against vectors (cicada), not against fungus
• Fight the fungus transmitted by the cicada by removing the dried up buds

• Big black beetle
• Eats on leaves of rhododendrons and other evergreen plants at night
• Damage from leaf edge corrosion
• Both beetles and larvae are dangerous; Larvae feed on roots
• Control by laying out old, rotten boards that serve as protection for the beetle; Beetles can then be collected
• Nematodes as beneficial insects effectively; chemical crop protection is virtually hopeless

Leaf spot disease

• Often occurring; easy to identify
• No clear damage pattern, as many weakness parasites can be triggers
• Typical brown lesions in the center and on the edge of the leaf; partial curling of the leaves
• Control exclusively through preventive measures (location and care) and chemical preparations

Powdery mildew

• Infestation with the Powdery mildew manifests itself in 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 leaf death, but can weaken the rhododendron through prolonged infestation
• Control through preventive measures before infestation and chemical preparations after the first signs of infestation; Use of chemical agents more effectively, the earlier the infestation stage

More information about common diseases and pests of the rhododendron and how to combat them can be found here.