In many places these days, hanging petunias are competing with geraniums as patio plants, as they grow quickly in a sunny spot and come in a variety of attractive colors. However, petunias can also be affected by a number of diseases that can severely limit flowering if left unchecked.
Petunias do not do well if they are too wet
Powdery mildew on petunias
Powdery mildew is a fungal disease that can spread quickly in dense stands of petunias without treatment. The occurrence of powdery mildew is favored when it comes to petunias that are exposed to wet, rainy weather without a protective roof. If continuously wet weather causes permanently damp plants, which are also not well dried by wind and sun due to their growth, powdery mildew is usually not long in coming. It can be recognized by the white coating that can cover all parts of the petunia like a floury layer. Possible prevention and treatment options include:
- the regular removal of withered flowers and plant parts
- installation in a rather dry location
- spraying with a water-milk mixture (9 parts water, 1 part milk)
- cutting out infected plant parts
Unlike downy mildew, powdery mildew only thrives on living plants, so removed petunias can be safely composted.
The root crown rot
The so-called root collar rot is a disease that is transmitted with the plant substrate used. The upper root area and the base of the stem turn black or brown before the entire plant withers and dies. In such a case, there is no salvation for the petunias. However, you should replace the potting soil and dispose of the old substrate if possible (not on the compost). In this way you ensure that the newly purchased or seed-grown young plants are not attacked again by the root collar rot.
Chlorosis: a deficiency symptom
Chlorosis is the yellowing of leaves, which usually occurs on the young leaves of petunias. Strictly speaking, this is not a disease, but a deficiency symptom caused by too few nutrients in the plant substrate. This often occurs when petunias are overwintered in the same window box for several years without significant fertilization. Since it is usually chlorosis due to iron deficiency, foliar fertilization with a special iron fertilizer often helps.
tips
Deficiency symptoms in petunias are often not necessarily due to diseases, but can also be a symptom of persistent wetness in the root area. Especially in the winter quarters, petunias should only be watered very sparingly, otherwise they can easily die off due to root rot.