Yellow leaves on rhododendrons indicate an iron deficiency. Under the so-called Azaleas also often suffer from chlorosis due to incorrect pH.
Rhododendrons, which are bog plants, are particularly susceptible to chlorosis. In the case of chlorosis in rhododendrons, there is often an indirect iron deficiency. As a result, not enough of the green pigment chlorophyll can be produced. Photosynthesis is no longer possible without the dye. In addition to the unsightly leaves, this is the main reason why bleaching should be treated.
Recognize chlorosis
The symptoms of chlorosis are very easy to recognize, especially in rhododendrons. If the leaves become yellowish, whereby the leaf veins often remain green, chlorosis is present. As already mentioned above, an iron deficiency is responsible for this, which is actually not at all. Most soils contain enough iron, but above a certain pH value it is very difficult for rhododendrons to absorb it.
Prevent yellow leaves on rhododendrons and azaleas
The heather family is dependent on a relatively low pH value of 4.5 to a maximum of 6. Otherwise the plants are no longer able to absorb enough iron and iron deficiency chlorosis occurs. To ensure a sufficient supply of iron, the pH value in the soil should be measured before each planting. Many companies bid for it special test sets at. If the pH is 6 and above, it should be generous before planting Rhododendron soil be incorporated. If you have a calcareous site and don't feel like doing any major digging, then try the INKARHO varieties. There the plants are refined with bases that can also cope with higher pH values.
Chlorosis and bleaching: treat and combat
In the case of severe chlorosis, foliar fertilization should be carried out. As a result, the leaves are briefly supplied with iron again. If possible, only leaf fertilizers should be used, as normal fertilizers are too concentrated and can lead to leaf burns. In addition to foliar fertilization, normal fertilization can also be used, but then iron should be fertilized in chelate form. The chelate in combination with the iron is absorbed much better by the rhododendron. In either case, you will only get rid of the chlorosis for a short time. If the pH value in the soil is too low, you will repeatedly have problems with chlorosis in your rhododendrons.
tip: If the reason for the iron deficiency is not the pH of the soil but the actual amount of available iron, you can use an iron-containing organic fertilizer such as our Plantura Organic hydrangea fertilizer use.