For a rose lover there is hardly anything more annoying than the lack of a rose blossom. Months of work and loving care - and then the flowering that rewards all effort does not occur or occurs only very poorly. There are various causes for this, behind which a fungus, a virus or even harmful insects can be found. We have compiled the most common reasons for missing or stunted flowers in this article.
Rose diseases can also be recognized on buds
Fungal diseases
Fungal diseases are very common in many roses, mostly due to improper care, too humid or too hot weather or an unsuitable location. Many fungal pathogens prefer to attack the leaves, but can also spread to shoots and even the flowers. Once this happens, it is usually an advanced stage of the disease.
Gray mold (Botrytis)
Gray mold (often referred to as "botrytis" after its causative agent) when it affects roses is also known as "stem and blossom rot" for good reason. This disease only occurs in summers with very high humidity and is reflected in the greyish fungal growth on leaves, buds and young shoots. In addition, these parts of the plant form brown, dry spots - affected buds and flowers then often look as if they have dried up. If this disease breaks out, only a radical pruning down to the healthy wood will help - the buds and blossoms can no longer be saved anyway. Never throw the clippings in the compost, but dispose of them together with household waste. Also avoid over-fertilization, especially with nitrogen, because this favors colonization with the botrytis fungus.
powdery mildew
Powdery mildew also occurs primarily in warm and humid summers and is primarily favored by the wrong choice of location. An infestation first appears on the leaves, but at an advanced stage it spreads to the shoots and buds of the rose. Affected plant parts continue to grow, but look very deformed. Buds don't open. Here, too, only a vigorous pruning and good ventilation of the rose will help, if necessary you should plant it in a new location. Sensitive rose varieties can be sprayed with plant strengtheners as a preventive measure.
tips
When the rosebuds initially grow healthy but are oddly shaped and quite thick, but eventually only grow into a small and stunted flower, the common cause is an infestation of thrips. These are tiny, black thrips that prefer to colonize healthy flowers and buds. Many blossoms of a rose can be affected, but also only a few.