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Hydrangeas With Red Spots

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Red spots can be the first sign of trouble on your flowers of any type, and hydrangeas are no different. Whether in your garden, your flower patch or in your house, these red spots can destroy the look of the flower. The spots are caused by a variety of fungi and are especially prevalent in three distinct types of hydrangea. In all of these flowers, though, you can treat the fungi and the red spots with proper care.

Causes of the Fungus

Fungus can appear on your hydrangea flowers for a variety of reasons, but it is most often the case that red spots are caused by weather conditions. The conditions that can produce these measles-like spots on your hydrangeas occur when a certain bacterial pathogen is produced on the plant. This happens where there are warm and wet environments in the late spring or early summer, around the end of May and beginning of June.

Types of Hydrangea Affected

Macrophylla hydrangea plants are the ones that are most commonly afflicted by these red spots and they are the ones where the spots tend to be the most noticeable. This is because the macrophylla plant, also known as a mophead hydrangea, features the largest leaves of any hydrangea plant. The other types of hydrangea that frequently can be found with red spots are the oakleaf hydrangea and the H. arborescens hydrangea plant. The disease is often most severe on the oakleaf plants.


When the ground and air are both moist, there will be more bacteria present than at any other time, and these types of bacteria prey on the leaves and flowers of the hydrangea plant. Once the plant is infected with the bacteria through plant tissue and openings in the flower, the red leaf spots begin to appear all over the leaves. This can be caused by fungus already existing on nearby foliage, splashing rain and irrigation from other sources.

Managing Red Spots

If you have red spots on your hydrangea plants, there are a number of things that you can do to make sure that this problem does not get out of control. When the spots first appear, you should locate all leaves with the red spots and cut them off. You should also remove any non-natural forms of irrigation or moisture as well as any standing or stagnant water. Finally, you can purchase and use a fungicide to help remove any current bacteria and prevent future bacteria from spreading to the plant. These products are available at lawn and garden centers. Follow the product instructions so that you don’t injure the hydrangea with too much fungicide.

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