Celebrate
One of Natures Beauties with the

Scottish Rhododendron Society

Frequently Asked Questions

Q. Why has my rhododendron failed to flower?

A. Flower buds are produced in the autumn, for flowering in the following spring. Weather conditions in the autumn will dictate bud set. A particularly dull autumn will produce less flower buds. If the plant has flowered particularly well the previous year it may need a year off.

Dwarf varieties prefer to be in an open spot for full flowering. If the soil is lacking in nutrient, other symptoms would be apparent, but you can try an ericaceous fertiliser when the new growth starts to emerge. Apply sparingly, and not after July.

Q. My rhododendron’s leaves have brown spots that appear on both sides of the leaf. The leaves become yellow and drop off leaving a sparse plant. What is this and what can I do about it?

A. This is powdery mildew.

Spray with a systemic fungicide, but in a severe infestation, the plant may eventually die. Some varieties are more prone than others.

Plant mildew resistant varieties.

Q. My rhododendron has branches that are healthy and some that are dying, why?

A. Is the site too wet?

Rhododendrons like to be in a damp but well drained situation.

Honey fungus can produce these symptoms.

There is no cure at present but if drainage is improved and the plant is happy to start with, it can be more resistant.

Q. My rhododendron’s foliage has become yellow all over, what can I do?

A. This could be chlorosis from lack of iron. Try feeding with an iron chelate. If unsuccessful, a soil analysis is necessary.

Q: Should I worry about a soft brown coating on the undersides of the
leaves of some of my rhododendrons?

A: No. This is normal. It is called indumentum and may help the plant to conserve water.

Q. Why do some of my rhododendron’s leaves look a deformed shape, but otherwise green and healthy?

A. This will be damage to the growth bud from a late frost. Leave and hope the weather conditions are better for the next season.

Q. Why does my rhododendron curl up its leaves in cold weather?

A. This is a normal response of some rhododendrons to sub zero temperatures, and is thought to conserve water.

Q. My evergreen azaleas have some deformed enlarged leaves, is there something I can do to make sure this condition does not spread?

A. This is leaf gall. Remove the infected leaves and dispose of them. Do not add them to the compost heap.

Q. Something has eaten notches out of the edges of the leaves, what should I use to protect the foliage?.

A. This is vine weevil. Control can mean inspecting the plant after dark when the adults come out, and removing them. Products containing nematodes that infect the weevils are now available. Avoid general insecticides because the weevils are less susceptible than their predators.

If you have a problem with a rhododendron, address it to enquiries@scottishrhodos.co.uk and we shall do our best to help.

(Photos by John Roy ABOVE RIGHT - Mildew , ABOVE LEFT- Honey Fungus (Armillaria) , BELOW RIGHT- Indumentum, BELOW LEFT - Azaleas)

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