Potted rhododendron, ideal for terraces and balconies

Rhododendron in a pot

Rhododendrons are nice shrubs perfectly suited to being grown in pots.

Key Potted Rhododendron facts

Family – Ericaceae
Type – shrub

height – 26 to 32 inches (0.6 to 0.8 meters)
Exposure – part sun and shade
Substrate – heath soil

 – evergreen
Flowering – March to June

Here are our tips to ensure your potted rhododendrons will develop and bloom year after year.

We recommend choosing dwarf species for growing in pots, since these are varieties that never grow taller than 32 inches tall even when mature.

Planting potted rhododendron

Potted rhododendrons, just like their counterparts planted in the ground, require well-drained soil to avoid all contact of roots with stagnating water.

Best place to put potted rhododendrons

  • For pots, it is best to choose shaded places.
  • Avoid drafty and windy spots.

How to choose an appropriate pot for your rhododendron

The substance that makes the pot is irrelevant, as long as the pot or garden box is sure to have water drainage outlets at the bottom.

  • Double-check that the pot does have a hole.
  • The pot’s size is also important, it shouldn’t be too big.
  • It is good to start small and up-size your pot every 2 to 3 years (except if you plant to grow your rhododendron in a large pot that is not designed to be moved around).

How to choose the substrate for growing in pots

Potted rhododendrons need heath to grow well.

  • Start with a bottom drainage layer made with clay marbles or pebbles, maybe an inch thick.
  • Fill the pot or garden box with heath mixed with special planting mix.
  • Follow our advice on planting heath plants and shrubs.

Pruning potted rhododendron

Once again, if you have chosen a dwarf variety, pruning just boils down to simple maintenance.

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

Watering potted rhododendron

Like most potted plants and shrubs, watering is crucial because the plant’s needs are very different from the needs of their ground-planted counterparts.

  • Substrate must remain moist, because rhododendrons are vulnerable to drought.
  • Water only when the soil surface is dry.
  • Add heath plant fertilizer regularly.

Watering potted rhodos in summer and winter

In summer, this probably translates into watering every other day. Fertilize only every fortnight, though.

In winter, watering should be greatly reduced. Frequency will drop to around once a week or even every two weeks, depending on the weather. Don’t give the plant any fertilizer at all from November to March.

Problems occurring when growing potted rhododendron

Rhododendron leaves and buds turn brown

This 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.
  • If this is the case for your potted rhododendron, reduce watering a little bit.

Fertilizing with special heath plant fertilizer at the end of winter strengthens rhododendrons, 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.

Potted rhododendron diseases

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.

Smart tip about potted rhododendrons

Pine bark mulch added on top of the soil in a layer an inch thick helps solve a good number of issues.

  • It retains moisture and cools the soil.
  • It raises soil acidity, which heath plants require.
  • It hinders weed growth.

Credits for images shared to Nature & Garden (all edits by Gaspard Lorthiois):
In garden boxes by Flower Council Holland / the joy of plants