After flowering and a wet spell in late spring I often give the Rhododendrons a top dressing of peat (Agh! A fungus called phytophthera takes hold if the roots are in overly damp conditions. It has lost all but perhaps 10 leaves which are producing flowers. Winter’s colder temperatures keep the leaves’ green chloroplasts from turning brown even after they are damaged. The excess of heat may not have prevented these shrubs from completing their biological preparedness for winter, but it did ensure that many plants started winter with unresolved stress-related problems. The plants are able to survive and bloom for many years. The other cause for dead branches on an otherwise healthy looking plant could be an infestation of Rhododendron stem borers. Try some commonsense housekeeping but leave the pruning shears in the shed. Rhododendrons (including deciduous azaleas) may be attacked by several diseases, causing unsightly foliage or a lack of flowers. Box 330966 Charlotta Wasteson / Flickr Creative Commons. Finally, if you create the right conditions most rhododendrons will be subject to fungus diseases. If you feel the need to fertilize, do so sparingly and with something organic instead of the blue colored liquid soluble fertilizers. Most rhododendrons will begin to grow in the next few weeks, showing you where they may need to be pruned, or that they don’t need to be pruned at all. Look out for plants with the Award of Garden Merit including the following Lepidote species Augustinii, Edgeworthii, Keiskei, Racemosum and Yunnanense. Use fungicides and follow the directions in the bottle. Rhododendron stem borers are not typically deadly, but an untreated infestation can be troublesome. The Rhododendron genus is a hugely diverse group of plants that includes closely related azaleas. The staff at the Experiment Stations is extremely helpful and will explain how to find and treat the plants with insect damage. I still like the leaf colours, textures and shapes and Rhododendrons are easy to for. Why the sudden appearance of damaged leaves? Check to see if the stem tips of your rhododendron are still alive, look for physical damage and remove any broken branches, and keep an eye out for stem borers. The adult borer is a moth, which lays eggs typically at the base of the shrub or at the bottom of the v-crotch of two branches. I find the canopy of Rhododendron leaves works well keeping weeds down. So any energy put into the seedheads is energy lost from next years plant and flowers. E-mail: [email protected] Elepidote species are generally larger and AGM’s include Niveum, Morii, Fluvum, Arboreum and Decorum. West Hartford, CT 06133-0966, Phone: 860-529-8713 It can be a long job on a large Rhododendron but I pinch out the seedheads to divert energy back to the shrub and give the leaf buds space to develop. Frigid temperatures, drying winds, heavy snow loads, and intense sun light can all impact a plant. If the shrub has been growing healthy and all of a sudden has dead branches, the shrub likely is suffering from fungus disease. Rhododendron are often planted in afternoon shade so hot summer sun won’t burn the leaves. This spring, many have turned completely brown or else the leaves of specific branches have turned brown even though the rest of the shrub looks healthy. Cut off dead wood and flowers for a low-maintenance prune. You may also find flower buds dried and brown in their center, but if you’re lucky, they will still be green. Some of the most common dangers to your rhododendron include aphids, root rot and Japanese beetles. The results of the disease are seen during the late spring when the plant is just beginning to grow and all of a sudden it drops dead. It can be a long job on a large Rhododendron but I pinch out the seedheads to divert energy back to the shrub and give the leaf buds space to develop. The damage can be traced to one or more of three problems: heat stress from last summer, infestations of Rhododendron stem borers, and/or our harsh winter weather from these past few months. Check the rhododendron for fungus disease. And, don’t forget about your rhododendrons when the weather turns hot and dry; if nature doesn’t provide any rain, a little bit of water each week will reduce their stress. There are more than 900 species in the Rhododendron genus, which vary greatly. Placing a layer of mulch or compost 2-3 inches thick under your rhododendron will help keep its roots cool and moist this summer. Failing to deadhead is not to say leaving the shrub to its own devices will be a failure but as we are growing for ornamental purposes every bit to care helps. To test this theory, you can check the stems to see if they look full and plump, or wrinkled and dry. Your email address will not be published. Those buds are still alive. And this past winter we had it all. To see if this disease is the problem, you'll need to do a little digging. It only takes a little practice, you soon pick up the knack without causing any damage. The evergreen leafed species of Rhododendron are just that, they remain green throughout the winter months. Any brown leaves will drop off as the new growth emerges. June was a deluge, followed by a hot, dry July. Those buds are dead. Rhododendron are shallow rooted, with their roots mostly growing in the organic-rich layer on top of the soil to maybe two or three inches down into the soil, so they are highly susceptible to damage from extremes of heat, cold, rain, and drought. Required fields are marked *. Blooming rhododendrons look like colorful, puffy clouds floating through the landscape, so when they don’t deliver, not only is it a huge disappointment, but a cause for concern for many gardeners. Had the snow melted between storms, the damage to rhododendrons would not be bad, or nearly as bad as what we are now seeing across the state. The eggs hatch and the immature caterpillars bore to the center of the stem and tunnel their way up the inside of the stem. Is my Rhododendron dead ...or not? To me it is therapeutic on a warm spring afternoon to be helping channel the natural energy into plants that have given so much pleasure already. The latter is … Soon the display of colourful Rhododendrons will falter and be over for another year. Dry looking stems will have buds that will take some effort to break off the stems. I hear some of you say but it is the natural ericaceous medium for Rhododendrons). Agricultural Experiment Station, either in Windsor, or New Haven. Let’s assume you are seeing damage from stem borers. It is not worth letting the seedheads fill up and develop as you are unlikely to be trying to breed your own from seed. This heat killed many small roots in the topmost layer of soil, preventing rhododendrons from adequately absorbing water and nutrients. Look at the bark on a stem or main branch of many rhododendrons and you will see tiny buds, little pink dots about the size of a pinhead that pepper the surface of older branches. You can find them at If the soil is boggy, heavy clay or compacted, rhododendrons will not grow for long and will likely die. In some cases, plants with a single branch of browned leaves may have been damaged by the weight of snow, which could bend the stems enough to cause vascular damage. Is my Rhododendron dead ...or not? Here you can see the seeds have been removed and added to the compost heap. Save my name, email, and website in this browser for the next time I comment. P.O. Kevin Wilcox is the owner of Silver Spring Nursery in Bloomfield, and is a member of the CHS Board. Pinching the often sticky seedsheads, I give a twist to break the stem just above the new leaf joint. Fungicide application in late spring and summer help the shrub to recover. Generally there are two leaf buds for each dead flower. It usually attacks plants that are under stress due to drought, too much sun or late frosts. In many cases, the plants can be saved, though they may be set back some. The easiest style of pruning is trimming off any dead or dying parts of your rhododendron with pruning shears. In Praise of Rhododendrons | Gardeners Tips, Housekeeping for Small Rhododendrons | Gardeners Tips. Dead leaves will look yellow or brown, and dead branches will be crispy and snap easily. This past year we saw all four extremes, with one after another increasing the stress on our plants. It is during July and August when rhododendron are finishing their yearly growth, forming flower buds for spring, and getting ready for winter. The light green new buds will generate leaves and new branches that can develop in the space now vacated. Cold temperatures resulted in the snow staying around and not melting.