With their pompous flowers and the great variety of colors, hydrangeas exude a special charm. But the ornamental shrub does not always present itself as expected. Pests and diseases cause an unsightly appearance. What methods of prevention are suitable so that the leaves do not wither? What measures should be taken if a flower does not form? And what are the reasons for a change in growth form? Anyone who knows the answer to these questions will be able to successfully remedy the damage.

The most common types of damage and diseases

To nurse a hydrangea back to health, early detection of the disease is important. Different symptoms indicate different ways. However, this is no coincidence. Most diseases are caused by specific triggers. Come into question

  • Fungal infections
  • Bacterial infections
  • Care errors

Fungal infections

Hydrangeas not only delight people with their lush flowers. Fungi also like to nestle on the ornamental plants and transmit diseases.


Powdery mildew is transmitted by a hose or algae fungus, which occurs in two types:

  • powdery mildew (fair weather mushroom)
  • downy mildew (bad weather fungus)

In addition to roses and vegetables, downy mildew in particular often attacks ornamental plants. The parasites owe their nicknames to the climatic conditions that promote their occurrence. Powdery mildew prefers warm temperatures. 20-25 ° C and dry spring are the ideal conditions for its occurrence. The pest spreads via insects and the wind. It attacks the leaves, buds and flower stalks of the plant, with symptoms only appearing on the upper side of the leaves. Downy mildew, on the other hand, can be recognized by damage patterns on both the top and bottom of the leaf. However, this type of mushroom only targets the leaves. According to its nickname, it prefers cool temperatures around 15-20 ° C and high humidity.

Powdery mildew

  • white coating on the upper side of the leaf, easy to wipe off
  • later the coating turns brown or grayish
  • Formation of necrosis
  • Leaves roll up
  • if the infestation is very severe, the hydrangea dies

Wrong mildew

  • yellow, white or purple coating on the underside of the leaves
  • yellow to red-brown spots on the upper side of the leaf
  • stagnant growth
  • Hydrangea dies completely


In the case of powdery mildew, it is particularly important to analyze the causes. Moreover, some home remedies only help against powdery mildew. Fortunately, it is usually possible to finally fight the pest without using any chemicals. Proven home remedies are:

  • Garlic stock
  • Field horsetail broth
  • Milk-water solution (only helps against powdery mildew)
  • Baking powder or soda water solutions (only helps against powdery mildew)
  • natural predators such as ladybugs
  • Plant partners such as chives, garlic, basil, thimble or chervil
  • biological pesticides
  • Nettle manure
Tip: The home remedies mentioned are very easy to make yourself and are sprayed onto the hydrangea at regular intervals. Since they contain substances that the mildew-carrying fungus eschews, they also serve as a preventive measure.


Gray mold, also known as botrytris, occurs when the air humidity is high. Regular ventilation is particularly important when the hydrangea is overwintered. Heavy soil also favors its development.


  • grayish, powdery coating on the leaves
  • Flowers turn brown and wither


  • Water hydrangea only in the morning
  • Avoid humidity
  • Thinning out the hydrangea regularly
  • cut off affected shoots

Leaf spot disease

The causes of leaf spot disease are also high humidity and nutrient-poor soil conditions.


  • black spots with a brown border
  • later these places tear open
  • Leaves turn yellow


  • remove the affected parts of the plant
  • enrich the soil with nutrients for prevention

Bacterial infections

In addition to fungi, bacteria are one of the most common causes of diseases in hydrangea. Unfortunately, measures are less effective with viruses. Finally, in the worst case, the entire bed must be destroyed. It is also no longer possible to replant on the spot.

Hortensien Virus

The hydrangea virus is caused by mycroplasmas and viruses.


  • slight growth
  • unusually small inflorescences
  • dull leaves
  • reddish or purple discoloration of various parts of the plant


  • no effective measures known (neither for control nor for prevention)
  • be sure to renew the floor

Hydrangeas greening

The hydrangea greening is caused by phytoplasms and bacteria. Insects often drag the viruses in. Before the plant dies, it shows a poor appearance.


  • small green leaves form from the stamens and the corolla
  • Growths possible
  • Leaves turn yellow
  • excessive budding


  • also no treatment of the causes possible
  • complete renewal of the bed

Care errors

Gardeners are mostly powerless against the transmission of diseases to the hydrangea by insects or the wind. In some cases, however, the causes lie in one’s own actions. In the long run, care mistakes can also lead to illnesses.


Chlorosis is a typical nutrient deficiency in hydrangea. Most of the time, the plant lacks iron, but less often it lacks copper or zinc. However, if the symptoms show up in older plants, the soil does not provide enough

  • Potassium
  • Magnesium
  • nitrogen
  • rarer phosphorus


  • yellow leaves with green veins
  • Discoloration begins at the leaf tips


  • Rhododrendron soil, peat or leaf compost lower the pH value of the soil
  • Use iron fertilizer
Note: In addition to a lack of nutrients, too high a base content in the soil can be responsible for chlorosis. Therefore, the disease occurs more often in pink hydrangeas. A soil analysis with a test strip from the hardware store gives you certainty as to what causes the disease.

Fungi, bacteria or care mistakes are mostly responsible for diseases of the hydrangea. While fungal infections and unfavorable conditions are easy to fix, there are no measures against viruses. Before choosing any arbitrary treatment method, the causes should be carefully analyzed.

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