Rhododendron: planting cultivation care and flowering

The Rhododendron is a flowering shrub whose foliage is persistent. Ses abundant flowers with multiple shapes and colors depending on the variety, are grouped in spectacular inflorescences contrasting magnificently with the dark green of the leaves. Depending on its variety, this large shrub reaches between 3 and 5 meters in height. It can be used alone, in a group, on a lawn, in a rockery, associated or not with other heather shrubs and can also be grown in a large container. Let’s see where and how to plant a Rhododendron, what its maintenance needs are and look at its amazing flowering.

Planter un Rhododendron

The Rhododendron likes semi-shaded exposures but its foot must be able to be sufficiently sunny. It can acclimatize in an area exposed to full sun only if the soil is sufficiently moist. He likes them heath-type acid soils whose Hydrogen potential (pH) is 4 to 6, humiferous, fresh but perfectly drained because stagnant water is highly detrimental to it. The rhododendron does not tolerate drafts or calcareous soil because it is too compact, and fear the hot sun. Respecting all these conditions is essential to guarantee the recovery and then the development of this beautiful flowering shrub.

Rhododendron planting can be done in the month ofoctober or during the spring, always outside the frost period. It requires compliance with the following points.

  • Start by soaking the root ball by soaking it in water for about twenty minutes.
  • Dig a hole at least 40 cm deep and 100 cm in diameter because the roots develop rather horizontally.
  • Remove stones, plant debris, weed roots.
  • Place the shrub in the center.
  • Fill the planting hole with a mixture of 20% compost, 30% non-calcareous topsoil or potting soil for flowering shrubs and 50% heather soil. Note that a little sand can be incorporated into the mixture to promote drainage.
  • Press down well with your foot.
  • Water copiously.

It is recommended to mulch the ground at the foot of the Rhododendron in order to preserve the freshness. A pine bark mulch quite suitable. On the one hand, by decomposing over time, this type of mulch enriches the soil with nutrients, on the other hand it brings acidity to the soil. The mulch also protects the roots of the shrub against severe frosts.

Caring for a Rhododendron

Easy to grow, the Rhododendron is the pride of gardeners. It is not very demanding but it should not be neglected.


During the two years following the planting of the Rhododendron, it is essential to ensure that water frequently so that the earth is always moist. However, the roots must not soak in stagnant water, hence the importance of ensuring that this shrub is provided with well-drained soil and not calcareous. Watering a Rhododendron in a pot should be done as soon as the surface of the substrate is dry.

Rhododendron in winter

This remarkably floriferous shrub displays a beautiful hardiness. It therefore tolerates temperatures from -15 to -20°C well, and some varieties can even tolerate temperatures down to -30°C! Be careful, however, if it is grown in a pot. It is better to place it away from severe frost, if only to avoid the container bursting. A wintering veil is very useful in this case.

diseases and parasites

He is not very susceptible to diseases and parasites as long as he benefits from an appropriate situation and his foot is not immersed in stagnant water. Excess humidity can cause bud browning.

The limestone is responsible for the iron chlorosis recognizable at leaf yellowing. Adding heather soil to the surface as well as regular fertilizer for heather plants is usually enough to eliminate the problem.

This shrub can sometimes fall prey to the fungus Exobasidium vaccinii responsible for the leaf gall. There are then growths on some leaves that just need to be eliminated to get rid of this disease.

On the other hand, the Phytophtora cinamommi is a fearsome mushroom for the Rhododendron since it generally causes the total dieback of the shrub then not being able to survive there. Only the use of a fungicide can be effective if done early enough. But it is not easy to act early because the signs appear when the damage is already done.

The size

So that the Rhododendron retains its beautiful appearance, the faded flowers are removed gradually. Otherwise, pruning is limited to the removal of dead wood. Can also promote branching by reducing the foliage at the beginning of October. To do this, it is necessary to prune just above one eye.

Blooming Rhododendron

Flowering lasts for about three months. It is interesting to grow different varieties to enjoy a staggered flowering because, depending on the case, some flower from March, others until autumn. All are covered with sumptuous terminal inflorescences, composed of large flowers, sometimes up to 25 cm in diameter, in various colors, white, red, purple, pink, yellow, and even variegated or striped… Something to create splendid monochromes.

It is interesting to associate it with other heather plants and shrubs such as the Hydrangea, the Japanese Maple or the Azalea, the latter also being a Rhododendron. For information, in horticulture we generally call Azaleas (from China or mollis) or even deciduous Rhododendrons the deciduous varieties and Rhododendrons or Japanese Azaleas, those with evergreen leaves even if all these shrubs and plants belong to the same botanical genus.

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