The rhododendron is one of the most popular plants in gardens and parks. Its diverse shape, evergreen leaves and colorful blossom magic inspires every garden lover. In order to maintain healthy growth of heather plants, damage such as brown leaves or brown spots must be recognized and treated in good time.
Location, soil and weather damage
Despite proper care and optimal location, brown leaves and spots can affect the rhododendron. In order to take effective action, you need to know what is causing the disease.
Brown yellowish curled leaves - rhododendron is thirsty:
Before the rhododendron dies of thirst, it rolls up its leaves. With this protective measure, it reacts to long periods of drought in summer or dry, cold winter weather.
What to do? Do not wet leaves when watering to avoid sunburn. In winter, only water on frost-free days to avoid frost damage. A layer of bark mulch keeps the root area frost-free for longer.
Rhododendron brown leaves and brown border - frost damage
In dry, cold and windy winter weather, more sensitive, less hardy rhododendron varieties are at risk of frost damage. Recognizable by dead flower buds or brown leaves and leaf edges.
What to do? Cover with fir twigs or reed mats as additional wind and cold protection.
Cut back severe frost damage in spring.
Brown yellowish leaf blades - sunburn
When sunburned, unshaded leaf blades turn brownish-yellow. Shaded leaves show no damage.
What to do? Shade rhododendrons or transplant them to a partially shaded location without midday sun. Check the leaves regularly as the weakened plant is at risk of fungal attack.
Damage from fungus and mold
Variegated brown spots on rhododendron leaves can cause up to 20 different types of fungi, rust and mildew. Only a microscopic examination provides a detailed diagnosis of the cause.
Rhododendron brown leaves and brown buds
The main causes are fungal diseases such as
- Phytophthora
- Botryosphaeria
- Phomopsis
All three fungal diseases spread quickly. But rarely threaten the entire plant. In the case of Phytophthora infestation, for example, the central ribs of the leaves turn brown. The infection spreads from the inside out, and the leaves wither.
Brown tips, brown leaf margin - leaf spot disease:
The causes of this disease are different weakness parasites. The first clues are irregular brown spots on the edge or tip of the leaf.
Brown mottled leaf tip with mold - gray mold rot:
If brown spots with a greyish mold layer appear from the tip of the leaf, this is gray mold. The infestation spreads over the whole leaf. There is a risk of infection, especially in warm, humid weather
What to do? The right choice of location, good plant nutrition and leaf control help preventively. In case of infestation, treatment with fungicides is required at intervals of about 10 days. Collect defective, discarded leaves and dispose of them with household waste.
tips and tricks
Steer clear of rhododendrons with brown leaves or yellow leaves, these are signs of disease or nutrient deficiencies.