Rhododendron, special flowered shrubs


Rhododendron is among the most beautiful heath soil shrubs.

A few Rhododendron facts

Type – shrub

Height – 1 ⅓ to 16 feet (0.5 to 5 meters)
Exposure – part sun and shade
Soil – acid, heath soil

Foliage – evergreen – Flowering – spring

Planting, pruning and caring for them are steps that help enhance blooming and avoid diseases.

Planting rhododendron

One of the most important considerations when planting rhododendron is the need to have heath and well drained soil.

If your soil is chalky or limestone soil, it is recommended to dig a much larger hole and fill it in with heath.

Planting rhododendronRhododendron tolerates shade, part sun and even sunlit places, as long as it stays cool.

  • We recommend planting rhododendron in fall.
    Planting is tolerated in spring or winter, as long as it doesn’t freeze.
    If you wish to plant in summer, provide for regular watering at the beginning.
  • Choose a partially shaded or sunlit spot that never gets scorching hot.
  • Avoid flood-prone areas at all costs, because this shrub hates sitting water.
  • Follow our advice on planting heath plants and shrubs.

Propagating rhododendron

Making cuttings is the easiest and fastest technique to propagate rhododendron.

Preparing rhododendron cuttings can be done all summer long.

  • Collect 6 to 8 inch (15 to 20 cm) cuttings from non-flowering stems.
  • Remove lower pairs of leaves, keeping only the topmost one or two pairs.
  • If you so wish, dip the base of the cuttings in powdered rooting agents.
  • Place your cuttings in nursery pots filled with cutting soil mix.
  • Keep the substrate moist and put the cuttings near light, but not in direct sunlight.

Pruning and caring for rhododendron

It isn’t really necessary to prune rhododendron, so caring for them is easy.

Pruning is only needed if you wish to maintain the figure, reduce the size of the shrub, or balance growth:

  • Remove dead wood.
  • Remove wilted flowers regularly (deadheading).
  • To reduce shrub size, wait for the end of the summer and cut just above a bud so it will split into multiple branches.

It is important for the soil to remain slightly moist at all times, and for that the best solution is to mulch with pine bark mulch.

Problems with growing rhododendron

Rhododendron leaves and buds turn brown

Rhododendron varieties and diseasesThis is often due to poorly-draining soil, which means water is stagnating around the roots.

  • Rhododendron must never have stagnant water around its roots, water must flow away quickly.
  • It makes sense in this case to mix some sand into the soil. It especially helps to spread a layer of clay marbles or pebbles at the bottom of the hole to help water seep into the ground.

Rhododendron is actually more hardy than they are able to overcome excess water in the ground…

Finally, fertilizing with special heath plant fertilizer at the end of winter strengthens rhododendron, enhances their flowering and helps avoid diseases.

Leaves lose their color and turn yellow

This is generally due to excessively chalky soil, and results in what is called rhododendron chlorosis.

  • Adding a layer of heath the soil in the surface is recommended.
  • A supplement of heath plant fertilizer should also help cure the chlorosis.

Diseases and parasites attacking rhododendron

Rhododendrons are shrubs that resist diseases well when they are well settled in, roots have developed well, and growing conditions are favorable.

Inversely, if there is either excess water or excess heat, or it hasn’t been planted correctly, it is more vulnerable to various diseases, listed below:

Rhododendron withers, looks sad and stunted

This is one of Rhododendron’s most common diseases, and it is often too late when it shows.

  • It is usually due to a fungus that is called Phytophthora cinnamomi. This fungus often is lethal to rhododendrons.
  • Treatment must be swift and merciless, removing and destroying the infested portions of the shrub, but survival chances are slim.
  • Once all infested portions have been removed, treat with systemic fungicide, which is the only effective option against this fungus.

Blisters form on leaves

  • Even though this is not often critical, this fungus-based disease is due to Exobasidium vaccinii, and is more commonly called leaf gall.
  • Usually, it is enough to remove the leaves that host these blisters.

Learn more about Rhododendron

Landscaping with rhododendronThis is probably one of the most beautiful flowering shrubs to decorate your garden.

Rhododendrons boast amazing flowers at the very beginning of spring, and their leaves are gorgeous all year round.

This plant can grow to live very old and can even reach majestic sizes, some shrubs reaching heights of over 16 feet (5 meters).

Rhododendron flowers are grouped in bouquets that can span 8 to 10 inches (20 to 25 cm) across, with hues shifting in ranges of pink to red, including white and violet depending on the species.

Rhododendrons are particularly decorative, and are among those shrubs that are best suited to shaded areas.

Smart tip about rhododendrons

Since it is quite acidic, pine bark mulch is definitely the best mulching option.

Mulch the base of the tree in summer to keep a good level of moisture.

Credits for images shared to Nature & Garden (all edits by Gaspard Lorthiois):
Pink rhody by Birgit Röhrs under Pixabay license
Deep red rhododendron by Tatjana under Pixabay license
Golden orange rhododendron by Gosia K. under Pixabay license
Large rhododendron by Carl Stridsberg under Pixabay license