Although the hydrangea is one of the most robust and resistant plants, this garden beauty is not immune to diseases. Should the attractive hydrangea ever let its flowers droop or suffer from discoloration of the leaves, care mistakes are rarely the cause. Fungi and other diseases can severely affect the hydrangea, so quick action is required.

Diseases of brown leaves or flowers of the hydrangea are not always to blame; nutrient deficiencies can also be the cause

fungal diseases

In certain weather conditions, fungi thrive and can infest numerous hydrangeas and other plants within a very short time. In this case, it is important to react quickly to prevent massive damage to the hydrangea. The most common fungi are as follows:

Wrong mildew

This fungus triggers what is probably the most stubborn hydrangea disease. It occurs more frequently in connection with warm and relatively dry weather conditions. The whitish-grey fungal growth appears on the underside of the leaf and is therefore often overlooked in the early stages of the disease. On the upper side of the leaf, yellowish and later red spots can be seen, which are similar to the damage caused by other leaf spot fungi. In the advanced stage, powdery mildew can also spread to shoots, buds and flowers. If the infestation is severe, there is a risk that the hydrangea will die completely.

powdery mildew

This bad weather fungus is immediately recognizable by the floury dusty coating even for the layman. The powdery mildew fungus can be easily wiped off and only affects the upper side of the leaf. As the stage progresses, the leaves curl up and show necrosis. The plant begins to take care of itself, with severe infestation it partially dies.

control of powdery mildew

Powdery mildew must be combated consistently to prevent the disease from spreading:

  • Remove infested plant parts and dispose of with household waste. This prevents the fungal spores from spreading further.
  • Spray hydrangea with horsetail broth, garlic stock or tansy.
  • The microorganisms contained in milk or whey support you in combating powdery mildew and help the plant to develop resistance. The affected areas must be treated several times with diluted milk or whey.
  • Beneficial insects such as ladybugs or sawflies keep the fungus in check. Therefore, only use fungicides and insecticides in the garden that protect these animals.
  • In the case of a severe infestation, the chemical mace is often the only option. When applying the fungicides, strictly adhere to the dosage indicated on the packaging.

leaf spot fungi

With this fungal disease, the leaves turn yellowish and brown spots of different sizes form. The discolored leaf tissue thins out and is eventually shed by the plant. In addition to high humidity, leaf spot fungi are often caused by a poor supply of nutrients.

countermeasures

  • Remove all affected leaves and dispose of them with household waste. Fallen leaves must also be collected and destroyed to prevent reinfection.
  • Thin out the hydrangea regularly so that the leaves can dry off quickly.
  • Check the supply status of the hydrangea and fertilize if necessary.
  • If the hydrangea is heavily infested, spray it with a suitable fungicide.

Botrytis bud rot (grey mold)

You can recognize this disease by the light grey, fluffy coating that covers the buds. Gray mold is encouraged by high humidity and occurs, for example, if the hydrangea in the house is not ventilated enough during the winter.

prevention and control

  • Overwinter the hydrangea in a cool room, airing at least once a day.
  • Check humidity regularly.
  • Cut off affected plant parts.
  • In case of severe infestation, treat hydrangea with a fungicide.

Illnesses as a result of care errors or deficiency symptoms

Diseases caused by incorrect cultivation conditions can usually be combated without any problems and the hydrangea recovers quickly.

chlorosis

In this disease, the foliage yellows from the top and turns brown in the later stages. If this damage occurs on the older leaves, the hydrangea lacks potassium, magnesium, nitrogen and, in rare cases, phosphorus. If, on the other hand, the leaf damage shows up on the freshly sprouted leaves, the hydrangea usually lacks iron. Less commonly, a lack of copper or zinc is responsible for chlorosis.

Iron deficiency often occurs when there is an excess of lime in the soil. That is why pink or red colored hydrangeas are more often affected by this disease. They depend on a soil pH value of over 6 for the expression of their flower colour. In order to change slightly acidic soils into alkaline ones, lime must be used frequently and the hydrangea can no longer absorb enough iron.

remedy

  • To be sure which nutrients the hydrangea is missing, a soil analysis is recommended.
  • Acidify overly limed soils with leaf compost, peat or rhododendron soil.
  • In case of iron deficiency, give Ferramin foliar fertilizer.
  • In the future, fertilize with a special hydrangea fertilizer with an iron content.

tips and tricks

If the hydrangea only grows very poorly and forms small inflorescences, it is suffering from hydrangea virus. Unfortunately, this disease caused by mycoplasma or viruses cannot be treated and it cannot be prevented either. The plant must be discarded and you must not plant any other hydrangeas in the same spot.

Category:

Vegetable garden