Some varieties, especially species, take many years to flower. This fungus can attack and kill rhododendrons in the woodland garden or areas where tree stumps are prevalent. Particularly those in Section Pognanthum. Mix with a wetting agent for best results to help the pesticie adhere to the leaf. Digging out a dead plant killed by honey fungus will usually reveal the tell-tale black bootlaces which have run through the root ball and into the stem, virtually strangling it in severe cases. Deer and rabbits. In really severe infestations, it may be necessary to poison rabbit warrens using sodium cyanide or similar gasses. Moving the plant away from overhanging branches or cutting them back can help. Good hygiene, adequate air circulation and moderate use of fertiliser all help prevent the diseases. Pyrethroids: Deltamethrin (e.g. They are characterised by the sudden wilting and death of a branch or part of a plant and tend to attack where plants have been physically damaged in some way. Evergreen and deciduous azaleas seem particularly prone. This requires a fine spray to allow the water droplets to adhere. 1. 3. It is found on wild populations of some species and also found in gardens on some species and hybrids, and especially on evergreen/Japanese azaleas and R. ferrugineum and its hybrids. Caused by late Spring or early Autumn frosts. Beware amateur gifts of Primulas, strawberries and other weevil favourites in case there are grubs in the compost. It can often take 6-9 months before you notice a sudden collapse. Vireya rhododendrons seem particularly prone to attack. You need to do this before the plant starts to suffer as root problems caused by poor drainage can be fatal. Not much can be done about this. The chorosis is far more likely caused by one of the reasons listed above: poor drainage, stravation, drought or poor planting. The rootball should be at or just below the soil surface. Move sunburned varieties into a more shady place if the problem persists. It can even strike before the flowers open. Freshly composted bark has been shown to have some root-rot resistant properties. In Germany, most varieties of rhododendron are grafted, which increases tolerance of poorly-drained soils. symptoms are pale spots on upper leaf surface, with corresponding brown/grey patches underneath: Control with fungicide from late May onwards. 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. If you see symptoms like this you should have your plants tested. A recently described disease which has caused much worry. Phone: 01738 860260 Email gardencentre@glendoick.com, The Cafe is OPEN from 9.30am (10am Sunday) to 4pm Last orders for hot food 3pm, Soup 3.30pm, Coffee & Cake 4pm, Phone: 01738 860265 Email cafemanager@glendoick.com, Glendoick Garden Centre, Glencarse, Perth, PH2 7NS. You can try to use heavy duty polythene to prevent bootlaces getting through the soil. Apply fertiliser April-May to Late June. Rhododendron ponticum is by far the worst host for it. Look at stem just above ground. Some hybrids such as 'Elizabeth' are very susceptible and are better destroyed. 1. In warmer climates, growing in shade and mulching will help to keep the soil temperature down. Rhododendron is suffering from lack of water: often due to competition from tree roots. Vitax Seaweed plus Sequestered Iron in conjunction with Vitax Azalea, Rhododendron and Shrub Fertiliser will cure the yellowing foliage of rhododendrons on neutral and acidic soils. by a wall, or in woodland for example. They grow on limestone in China. Lichen tends to grow on weak plants rather than causing the weakness. Most rhododendrons and azaleas came through well and most of those damaged have grown from below, at Glendoick. Hard pruning a badly infected camellia or rhododendron can be the best way to get rid of it. 6. 3. 4. Gardens with lots of old tree-stumps in the ground are at most risk Of course, one can glibly recommend that all tree roots be removed but this is impossible with the enormous root systems mature broad leaf trees such as elm, beech or sycamore.