![]() It coats the leaf upper surface with white in late summer. occidentale in their breeding: so paler colours. Roseclear, etc.Ī few rhododendron hybrids such as Anna Baldsiefen, Arctic Tern and Azaleodendrons are very susceptible. Rust: Black spots on upper surface, lower surface with orange patches: Control with rose fungicides. Some hybrids such as 'Elizabeth' are very susceptible and are better destroyed If the infections are mild, just live with it. Powdery Mildew: symptoms are pale spots on upper leaf surface, with corresponding brown/grey patches underneath:Ĭontrol with fungicide from late May onwards.Īny rose fungicide will do: myclobutanil (systhane), fungus fighter, roseclear etc. They tend to strike in dry weather and you'll find them on our under the leaves. For insects use a contact or systemic insecticide. This is mainly cosmetic but if it keeps happening you may need to move a plant to a more sheltered site or cover it up in frosty weather.Ģ. When the new growth buds begin to elongate before unfurling, the tips of the new leaves can be puckered by frosts causing them to distort when they unfurl. Caused by late Spring or early Autumn frosts Why has my rhododendron got crinkly leaves?ġ. We use dolomitic limestone on these to bring the pH to around 6 which they prefer. Particularly those in Section Pognanthum. Soil Too Acid Some rhododendrons dislike very acidic soil. The chorosis is far more likely caused by one of the reasons listed above: poor drainage, stravation, drought or poor planting.ħ. Adding iron chelates or sequestrine can help but most of this time this is an expensive waste of time. But in alkaline soil, rhododendrons take up too much calcium and not enough iron. Most of these are found naturally in soils. Mineral Deficiency Rhododendrons need specific minerals. You can lower/acidfy the soil pH before planting by applying sulphur as alumineum or iron sulphate.Ħ. Farmers do lime soil for crops but this washes out over 3 years or so. In Scotland virtually all soil is naturally acidic. You can have your soil tested but it is better to ask around as gardeners generally know if the local soil is alkaline or acidic. Use rainwater collected from rooves instead. ![]() Avoid watering with tap water if it is chalky. If you have alkaline soil, you will need to build raised beds and plant in peaty soil. ![]() ![]() Soil acidity is measured by the pH scale. Soil is too alkaline (unlikely in Scotland) pH 6 and higher. Think about thinning the shade or moving the plant if it is suffering.ĥ. Feed and water the plant and it will probably pick up. Rhododendron is suffering from lack of water: often due to competition from tree roots. Apply fertiliser April-May to Late June.Ĥ. Do not use membrane and bark as rhododendrons dont like this.ģ. Do not let piles of mulch bury the plant. If it has been in for a long time you may see new roots forming near the soil surface. If you cant feel the rootball then it is probably planted too deep. Rhododendron is planted too deep? The rootball should be at or just below the soil surface. You need to do this before the plant starts to suffer as root problems caused by poor drainage can be fatal.Ģ. Rhododendron drainage is poor: solution: lift plant and improve soil structure or move to better drained spot. This is a general sign of unhappiness and can have many causes:ġ. Why does my rhododendron with yellow or chlorotic leaves: So why has my rhododendron got yellow leaves? Reasons include: because they are too wet, too dry, planted too deep, starved (needing feeding), soil too alkaline, or soil is compacted: There are several reasons that this may happen. Rhododendrons which are not happy tend to show this by their leaves turning yellow. And they wont grow in areas with chalky/limey soil unless in raised beds. They wont tolerate deep and dry shade and poor drainage/heavy clay soil. Rhododendrons are quite easy to grow as long as you have well drained but moist acidic soil. What's wrong with my Rhododendron? The most common pests, diseases and problems of Rhododendron and Azaleas Rhododendron Expert Glendoick's Kenneth Cox discusses Rhododendron Problems, Pests & Diseases.
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