Rhododendrons are nice shrubs perfectly suited to being grown in pots.
Key Potted Rhododendron facts
Name – Rhododendron
Family – Ericaceae
Type – shrub
Potted height – 26 to 32 inches (0.6 to 0.8 meters)
Exposure – part sun and shade
Substrate – heath soil
Foliage – evergreen
Flowering – March to June
Here are our tips to ensure your potted rhododendrons will develop and bloom year after year.
- Discover all our advice on growing rhododendron
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.
- Discover all our advice on growing rhododendrons.
In garden boxes by Flower Council Holland / the joy of plants
Should you water regularly and feed during the summer and winter
Hi Peter! I just added a section to the “watering” paragraph to answer that. Jump up to it here.
I keep losing my Henry’s Red Rhododendrons.
I’ve planted them in the ground in the same spot and replaced them twice.
I’m thinking the ground is too wet where I have planted them.
I don’t want to give up.
I’m thinking of trying again in containers, buried in the ground to control the water that gets to the plant roots.
Will this work? What do you think? Can a Rhododendron live long term in a container buried in the ground?
Hi Todd, well, while I do recommend what you suggest in the pot-in-pot technique, I’m not sure it’s what you need in this case. For your idea to work, you’d need to have watertight containers because if there’s the slightest hole or crack, water will seep in anyways so your efforts will have been in vain. If the containers are watertight, however, it’s very difficult for excess water to drain away and your plants would drown: not good if it rains. A rhody can grow for decades in a pot, but that’s always an above-ground container where drainage is possible.
What I’d do in your case is to try to set your Rhodies up on a type of mound or low raised bed. First, make sure you add in lots of pine bark mulch to make it both high-draining and acidic, and before you even raise the mound, shovel out some of that heavy soil and replace it with lighter peat or peat equivalents, clay pebbles, etc.
Congrats on not giving up, by the way! That’s the spirit!
Thank you Gaspard. Your comments are very helpful.
Thank you for taking the time to help me out.
Todd
Pittsburgh
Hi Nature and Garden, I am hoping you can help. We bought a Rhododendron “Double Dots” and an Azalea Knaphill “Anneke” last year. They were both potted up in suitable containers in ericaceous potting mixture, well drained, in a dapple shaded position. So far we have not seen any flower buds on them. All the leaves are healthy on both plants, I had been watering them every other day but have reduced the watering to every third day. Both plants have had a liquid feed for this type of plant. Since having the plants we have not pruned them at all. Could you advise why we have not seen any flower buds yet.
In the same area that these two plants are we also have a camellia, which has flowered and gets the same watering and feed.
Regards,
Paul Wakeford
my container rhododendron leaves are not perky but look limp