Geraniums - which are actually called pelargoniums in botanical terms - are popular balcony flowers, but they are quite susceptible to various diseases, mostly caused by bacteria or fungi, especially if they are not cared for properly. The following article tells you what signs to look out for and what you can do about them.
Poor care can cause diseases in geraniums
pelargonium rust
Geranium or pelargonium rust is very common in geraniums and is caused by fungi that get onto the leaves with rain or rainwater. You can recognize this disease by brown leaves on the upper surface, while the underside is affected by brown and yellow pustules. Pelargonium rust is highly contagious, so you should separate affected plants as soon as possible and remove affected parts of the plant. However, you can prevent the disease by protecting your geraniums from rain and always watering the soil and never the leaves.
gray rot
Gray rot (often referred to as gray mold or botrytis) is also very common on geraniums. Another common feature is that gray rot, like geranium rust, is caused by excessive moisture. Infested plants show blackish spots and/or greyish fungal growths, especially on the leaves. Sometimes, however, the geraniums simply rot. In addition to excessive moisture, there are other causes of gray rot:
- Lack of light (wrong location)
- wrong watering
- rainy-cool weather
- Injuries to the plant (e.g. by pruning)
As with pelargonium rust, you can prevent gray rot by always watering the geraniums directly on the substrate, but never on the leaves, and by protecting the plants well from rain. Treatment is possible primarily through the timely removal of affected parts of the plant.
wilt
Wilt caused by bacteria is also highly contagious and requires separating infected plants. This disease is mainly caused by
- wet leaves
- excessive watering
- excessive fertilizing
- and injuries to leaves and shoots
caused - as with the two aforementioned diseases. As with these, you can also prevent bacterial wilt by protecting your geraniums
- position as sunny and sheltered as possible
- protect against constant rain
- water and fertilize properly
- never water on the leaves
- Avoid waterlogging
- and only use sharp and clean tools for cutting.
Wilting is characterized by the wilting of affected parts of the plant to the point of turning black and finally the entire plant dying off.
Yellow leaves on geraniums
Unlike the diseases previously described, yellow leaves on your geraniums are rarely caused by fungi or bacteria, but mostly by an inadequate diet. In other words, your geraniums are suffering from a nutrient deficiency; where it is mostly the trace element iron that the plants lack. You can quickly remedy this deficiency with a special iron fertilizer.
tips
If your geraniums only want to develop a few flowers or no flowers at all, this is often due to an insufficient supply of nutrients - but not in every case. You often fertilize enough, but with the wrong fertilizer. If this contains too much nitrogen, leaf growth in particular is stimulated and flowers have no more space.