Yellow leaves on rhododendrons: prevention and treatment
Yellow leaves on rhododendrons indicate an iron deficiency. Azaleas too often suffer from so-called chlorosis due to an incorrect pH.
Rhododendrons, which are bog plants, are particularly susceptible to chlorosis. Chlorosis on rhododendrons is often due to indirect iron deficiency. As a result, not enough of the green pigment chlorophyll can be produced. Without this pigment, however, photosynthesis is no longer possible. This, along with unsightly leaves, is the main reason why a bleached appearance should be treated. Find out what to do if your rhododendron has yellow leaves in this article.
How to recognise chlorosis
The symptoms of chlorosis are very easy to recognise, especially in rhododendrons. If the leaves become yellowish, with the leaf veins often remaining green, chlorosis is present. As already mentioned above, an iron deficiency is responsible for this, although it is not really an iron deficiency at all. This is because most soils contain enough iron, but above a certain pH rhododendrons find it very difficult to absorb it.
Preventing yellow leaves on rhododendrons and azaleas
These plants, which belong to the heather family, depend 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 lime-induced chlorosis occurs. To ensure an adequate supply of iron, the pH in the soil should be measured before each planting. Many companies offer special test sets for this purpose. If the pH is 6 and above, rhododendron soil should be generously incorporated before planting. If you have a chalky site and do not feel like doing a lot of digging, try the INKARHO varieties. These plants are grafted with rootstocks that can cope with higher pH values.
Chlorosis and pallor: treat and combat
If chlorosis is severe, foliar fertiliser should be applied. This provides the leaves with iron again in the short term. If possible, only foliar fertilisers should be used, as normal fertilisers are too concentrated and can cause leaf burn. In addition to foliar fertilisation, normal fertilisation can also be used, but in this case, iron should be added in chelated form. The chelate in combination with the iron is much better absorbed by the rhododendron. In both cases, however, you will only get rid of chlorosis in the short term. If the pH in the soil is too low, you will always have problems with chlorosis on your rhododendrons.
Tip: If the iron deficiency is not due to the pH of the soil but to the actual amount of available iron, you can apply a fertiliser containing iron, such as our Plantura Hydrangea Food.
- For beautiful hydrangeas with lush blooms in pots & flower beds
- Prevents common deficiency symptoms & supports healthy plant growth
- Long-lasting fertiliser that is free from animal products - child & pet friendly
