Rhododendron Care: Tips On Watering, Fertilizing & Cutting

The rhododendron blossom makes the gardener’s heart beat faster. But for a profuse bloom, it must be properly cared for and protected from diseases.

Rhododendrons (Rhododendrons) are one of the largest genera within the heather family (Ericaceae). With more than 1000 species worldwide, the rhododendron is geographically represented almost everywhere. It is therefore not surprising that it can be attacked by a wide variety of pests and diseases. We provide tips on proper care and effective control of pests and diseases so that your rhododendron can continue to bloom in all its glory.

Maintaining rhododendrons

The rhododendron is relatively easy to care for. However, at certain times of the year, he wants some attention from you. We reveal what you should pay attention to with the right care. Before we start, however, it should be said that certain points should be taken into account when planting the rhododendron. Rhododendrons want slightly acidic soil and abhor waterlogging. Many soils, especially in the southern United States, are more neutral to slightly basic. It can therefore be advantageous to dig a large planting hole and fill it with special rhododendron soil.

Water the rhododendron properly

Especially when the rhododendron plants are still small, they want to be watered regularly. However, waterlogging must not occur here, as the rhododendron, as a shallow-rooted shrub, is very sensitive to this. The bigger and older the rhododendron gets, the less often it has to be watered, as the roots are now stronger. Signs of the need to water can be hanging flower buds or curling leaves during flowering.

Note: You can water your darling at slightly longer intervals, but then with a little more water. Particularly during dry periods, water that is too small can evaporate quickly before it penetrates the soil.

Fertilize rhododendrons

The rhododendron is particularly happy about long-term fertilization. The best time for this is in spring, which means shortly after planting with freshly planted bushes. Work the fertilizer superficially in the root area so that the nutrients can be better absorbed into the soil. You can also mix horn shavings, compost, and/or coffee grounds with the excavated soil during the planting process and then put it back into the planting hole.

These fertilizers are all purely organic, some have slightly acidic properties for the soil and have a positive effect on soil life. While coffee grounds increasingly lower the soil pH value but are not a very large supplier of nutrients, the compost takes on the task of long-term nutrient supply. Horn shavings (or horn meal) do not affect the soil pH value, but also ensure long-term nutrient release with high nitrogen content. Those who prefer to fertilize regularly rather than using slow-release fertilizers will stop fertilizing from October to initiate the resting phase.

For your darlings who have already taken their place in the garden for a long time, the expert recommends giving the shrub an energy boost a few weeks before flowering with a mixture of mineral and organic fertilizers. You can find out more about this in the video.

In addition to the above-mentioned home remedies, there are also special rhododendron fertilizers on the market that cover the entire spectrum of nutrients and also (partially fully organic) deliver nutrients in the medium term. Primarily organic fertilizer is also suitable for rhododendrons. The long-term fertilizer releases its nutrients gently and over a longer period of time to the rhododendron and also supplies it with iron.

Note: Under special circumstances, second fertilization can also be carried out in summer. However, this is only necessary if a nutritional deficiency manifests itself in the form of yellow and withered leaves.

You can find out more about the correct fertilization of your rhododendron here.

Cut rhododendron

In principle, the rhododendron does not need any special pruning to bloom profusely. With increasing age, however, there is an increased lignification of the shoots, which is why a rejuvenation cut makes sense if necessary. A radical rejuvenation cut should be made before flowering, as this will not waste the energy reserves of your rhododendron unnecessarily and nesting birds will not be disturbed.

Use sharp secateurs to cut off old shoots so that the bare interior of the shrub gets light again. It is important to make sure that you cut the shoots at an angle. This way, no dew or rainwater collects on the open areas of the shoots, which could cause diseases to penetrate.

If you don’t want to make a radical rejuvenation cut, but only want to keep the shape of your rhododendron, you can carry out a comprehensive maintenance cut immediately after flowering. Here unsightly, diseased, and injured shoots are removed until you are satisfied with the growth habit of your favorite.

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Care for the rhododendron after flowering: break out flowers

After you’ve made a comprehensive pruning, there is still some good things you can do for your rhododendron. To do this, simply break off all withered flowers on the remaining shoots. This promotes the formation of buds in the next year and eliminates spore foci, which prevents infestation by fungal pathogens.

Transplant rhododendrons

You may need to transplant your rhododendron. We have summarized the best way to do this in a special article.

Rhododendron diseases

The genus of the rhododendrons is particularly susceptible to fungal diseases, but animal pathogens also wreak havoc in the evergreen foliage of the rhododendron.

Rhododendron has yellow and brown leaves

The discoloration of the leaves usually has two causes: Either the plant was cared for incorrectly or it was attacked by a fungus. To do something about the discoloration, the source of the damage must first be identified. Chlorosis from improper maintenance can either be caused by soil that is too calcareous or a lack of nitrogen. With fungal infections, different yellow or brown lesions form depending on the pathogen.