Flowering rhododendrons are a feast for the eyes. Keeping these beautiful trees is not easy, but not overly complicated either. A suitable location and, above all, the plant substrate are important. In addition, these shrubs must not be planted too deep. If a few basic things are taken into account when planting, nothing stands in the way of a rhododendron growing and thriving. You can read what these are in the following text. Inform yourself!


  • Heather family
  • Rhododendron is Greek and means rose tree
  • About 1,000 species
  • Lots of varieties, including hybrids
  • Distribution area huge, therefore different claims
  • Mostly evergreen shrubs
  • Also deciduous species and trees
  • Beautiful flowers in many colors, also multicolored
  • Flowering time from January to August, depending on the species
  • It is important to select the plants appropriately for the location
  • Most species and cultivars do not like midday sun
  • But there are also special breeds for just that
  • If you have difficult soil conditions, you should switch to Inkarho breeds (refined).

Plant rhododendrons

The genus Rhododendron is basically divided into two groups. Firstly, in the large-flowered, usually quite large-growing species and varieties, and secondly, in the small-flowered, mostly creeping and dwarf species and varieties. This subdivision is important to choose the right location for the plants. If they are not thriving, they will not thrive and become susceptible to disease and pests. The beauty of these decorative garden plants is quickly over.

Our three native rhododendrons are all flat-rooted. They rarely get higher than 1.20 m and need a special floor. The location is also crucial for the trees to feel comfortable.

planting time

The best time to plant rhododendrons is between late March and early May. At this planting time, it is of course important that the plants are then regularly and sufficiently watered so that they grow. Alternatively, the time between the beginning of September and mid-November is also suitable. This offers the advantage that roots form quickly.

  • Spring – late March to early May
  • Autumn – early September to mid-November
  • Potted rhododendrons can be planted all year round except during frost.


In order for rhododendrons to feel comfortable and thrive in the garden, the site conditions of their native forests must be simulated. Most of these trees do not like full midday sun, but they do not like too much shade either.

  • Almost all species thrive best in light semi-shade.
  • However, there are also types and varieties for a purely sunny place. Among these are the Yakushimanum hybrids.
  • A little wind-exposed place is good, so that the soil does not dry out so quickly and a certain humidity can be maintained.
Tip: Many experts for these great flowering plants recommend Scots pines as shade trees for rhododendrons. Due to the thin, long needles, the shade is quite light and these trees also have deep and sparsely branched roots that do not compete with the fine rhododendron roots. Oaks, yews and fruit trees are also suitable. On the other hand, willow, birch, linden and maple are unsuitable.

plant substrate

The most important thing about the plant substrate is that it has to be acidic. You can regulate the acidity by applying additional peat mulch. Pure rhododendron earth from the trade is also helpful. It lowers the pH.

  • Definitely acidic soil
  • He should also be humorous and relaxed
  • Air permeable to provide enough oxygen
  • Generally permeable so that excess water can drain off easily.
  • pH between 4.2 and 5.5
  • Inkarho rhododendrons also tolerate less acidic soils, between 6 and 6.5
  • Not too dry substrate, the plants need consistent soil moisture
  • Clay soil is unsuitable, it is too heavy for the fine roots.
Tip: If the soil conditions prove to be very unfavorable for normal rhododendrons, there is an alternative. Inkarho rhododendrons are a little more expensive, but these specially bred varieties will also grow in loamier, non-calcareous soils. Here, normal rhododendrons were grafted onto a special, relatively lime-tolerant grafting base. The soil must also be very loose and humus for these special breeds.

planting distance

The planting distance is important because rhododendrons spread over the years. Some grow very slowly, but there are also faster-growing species and varieties. So you should already have the final size of such a tree in mind when planting and not plant the rhododendrons too densely.

  • Slow-growing varieties (Yakushimanum hybrids and Japanese azaleas) 30 to 50 cm
  • Deciduous azaleas 50 to 80 cm
  • Vigorous rhododendron hybrids – around 100cm
  • Planting ground cover around the rhododendrons is beneficial. They form a closed plant cover and are then gradually pushed out by the spreading shrubs.

The planting

The roots of the rhododendron grow very close to the surface and spread out extensively. The root structure is very fine. If you don’t have the right soil for these plants in your garden, you have to replace it and prepare it accordingly.

  • Dig the soil 50 cm deep for each plant. The diameter should be about 150 cm.
  • The old soil should be replaced with a mixture of roughly equal parts bark compost, sand and preferably well-seasoned cow manure.
  • Where there is a risk of waterlogging, a 10 cm thick layer of coarse building sand should be placed in the bottom of the excavated hole as drainage.
  • On very sandy soils, on the other hand, it is sufficient to spread bark compost and cattle dung underneath.
  • Planting hole 2 to 3 times the size of the root ball
  • Before planting, immerse the root ball in water until no more air bubbles rise.
  • Carefully place the rhododendron in with its root ball.
  • Fill the planting hole with a mixture of soil and peat mulch.
  • Press on the earth, don’t step on it!
  • It is important that the plants are then watered well.
  • A watering rim around the plant is recommended for this, which enables effective watering.
Note: Never plant deeper than the rhododendron was in the nursery or in the pot. Do not cover the top of the root ball with soil. If a rhododendron is planted too deep, the sensitive root system dies and the plant dies. It is better to let the bale protrude about one to two centimeters from the ground.
  • It is also good to spread one or two handfuls of horn shavings in the root area, but only when planting in spring. When planting in autumn, only fertilize in the coming spring!
  • Never put fertilizer in the planting hole, always on the surface!
  • At the end, apply a layer of bark mulch or bark compost about five centimeters thick. It protects the soil from drying out and strong temperature fluctuations.
Tip: If possible, always water rhododendrons with lime-free water, so just use rainwater!

Transplant rhododendrons

Rhododendrons are relatively easy to transplant, even older specimens. Of course, it is important that the root ball is injured as little as possible. The best time for such a transplant is late March to early April and then again in September.

  • Prepare new location accordingly (see text above)
  • The soil must be prepared particularly well.
  • If possible, work on fairly dry soil.
  • Prick the flat root ball with a spade.
  • Pry out the bush with the spade.
  • Insert in the new place and fill up with soil.
  • It is important to cut back the rhododendron a little after transplanting .
  • In addition, the soil must be mulched.

Frequently Asked Questions

Can rhododendrons also be cultivated in tubs?
Yes, most species and varieties do, at least for a while. When the growing plants have reached a certain size, it is better to plant them out. Smaller species can be kept in a vessel for many years. It is important that this is protected in winter so that the root ball does not freeze through. It is usually sufficient to place it against a warm house wall, wrap it up thickly and, if possible, place it on styrofoam plates.

Does the root cloth have to be removed when planting?
Larger alpine roses in particular are sold wrapped in a ball of cloth instead of in a pot. This should be loosened when planting, i.e. usually simply untied. Place the rhododendron in the planting hole with the ball of cloth and simply untie it as soon as the plant is in the right place. Then you spread it out. Now soil can be filled up. The bale cloth rots over time. It doesn’t need to be removed.

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