When to plant rhododendrons?
- Botanical name
- Rhododendron
- Family
- Ericaceae
Rhododendrons are planted from October to April.
Rhododendrons are woody perennials.
A rhododendron does well in a pot of acid medium even where the beds themselves are not acid.
It is watered with rainwater, because hard tap water raises the pH around the roots. In a dry summer the watering is regular and thorough, and the ground around the bush is mulched. Left without water in summer, it drops its flower buds and does not flower the next spring.
A rhododendron needs no regular pruning, only dead wood and faded flowers are taken off.
Rhododendrons through the year
- planting
In short
Growing conditions
Are rhododendrons toxic to cats and dogs?
Yes. Toxic to people and animals, toxic parts: roots, stems, bark, leaves, flowers, fruit, seeds and sap.
Pests and diseases
Listed here is every problem for which the sources name this plant as a host. The problems are not listed in order of how common they are.
- Signs
- The plant dies suddenly, often in mid season and without any decline beforehand. Peel the bark at ground level and under it there is a white or cream sheet of fungal tissue, thin as the skin of a mushroom. In the soil there are black or brown strands like bootlaces. In late summer and autumn tufts of honey brown mushrooms with a whitish ring on the stalk appear by the stumps or over dead roots.
- Prevention
- The fungus spreads through the soil with its strands, from a few centimetres to a good hand's width below the surface, and infects the roots of a living plant when it touches them. So do not leave stumps and dead roots in the ground. No plant is completely resistant, but privet, lilac, viburnum, weigela, forsythia, butterfly bush, rhododendron, thuja and walnut are particularly susceptible.
- What to do
- There are no products. The only thing that works is digging out and removing every infected root and stump, which takes away the food without which the strands in the soil do not grow. A vertical barrier of rubber or thick plastic sheet, buried about half a metre deep and standing a few centimetres above ground, stops the spread into an unaffected part of the garden.
- Signs
- The foliage on one branch takes on a silver sheen and the branch then dies. Cut across, the dead branch has an irregular dark stain in the middle that does not follow the rings. On old dead branches bracket fungi grow later, with a whitish woolly upper side and a purple brown underside. A silver sheen without the dark stain in the wood is not this disease but the result of drought or cold.
- Prevention
- The spores are active from September to May and enter through wounds, above all through pruning cuts. Remove dead wood before fruiting bodies grow on it.
- What to do
- Cut the affected branch off as soon as you can, well below the point where the dark stain in the wood ends. Disinfect the tools as you go and remove the cuttings at once, because fruiting bodies go on developing on branches left lying about. Do not paint the wounds as a matter of routine, but do it where the disease keeps coming back.
- Signs
- The half round notches along the leaf edges in summer are the work of the adult beetles and do the plant little harm. The larvae are the danger: white grubs with a brown head eat the roots, the plant suddenly drops its leaves and dies, most often between autumn and spring.
- Prevention
- Most at risk are plants in pots and troughs. In a bed the damage is rarer. At repotting check the roots and the compost and pick the larvae out. You find the adult beetles in the evening with a light, when they crawl over the plants.
- What to do
- Pick the adults off in the evening, set sticky traps indoors and change the compost, removing the larvae as you go. There is no insecticide. As biological protection, water beneficial nematodes into the compost at the end of summer, while the larvae are still small.
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Related plants
The plant below is in the same botanical family (Ericaceae).
Sources about the plant: ASPCA Toxic and Non-Toxic Plants, GBIF Backbone Taxonomy, NC State Extension Plant Toolbox, Royal Horticultural Society, Wikidata. Checked between 14 and 28 August 2026. The problem descriptions also draw on: EPPO Global Database, University of Illinois Extension.