What Is Geranium Edema & How Can You Prevent It?

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Geranium edema is a physiological disorder usually caused by poor Geranium care or unfavorable environmental conditions. It is not a contagious disease, and it doesn’t spread from one plant to the next. 

Instead, it is typically caused by problems such as overwatering or improper temperature and can usually be resolved by evaluating and correcting problems with the environment. In this article, we share advice to help you do just that.

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How Do You Know Your Geraniums Have Edema? 

All Geraniums are subject to this disorder, but Ivy Leaf Geraniums seem most prone to it. To determine whether your Geranium is suffering from edema, look for these symptoms: 

  • Yellow spots on the leaves’ topsides between the veins and along the leaf margins of older leaves. 
  • Blister-like water pustules opposite these yellow spots on the leaves’ undersides. 

If you miss these symptoms and the disorder progresses, you will see: 

  • Brown scabby spots on the leaves
  • Yellowing leaves 
  • Leaf loss 

When the condition gets to this stage, it looks rather like bacterial blight, and it is easy to misdiagnose. 

What Are Some Of The Causes Of Geranium Edema? 

Edema will result if the plant takes up more water than it can process. This can happen if the soil is moist and warm, but the air is cool and moist. 

When this happens, the plant takes up moisture from the soil, but it cannot release it into the already humid atmosphere. This causes water retention and blistering on the leaves. 

You can expect this to happen in low light and poor ventilation situations. In addition, if the weather is cool and cloudy for several days, it may trigger Geranium edema.

The presence of two-spotted spider mites may also cause edema, which may explain why Ivy Leaf Geraniums are more subject to edema. These Geraniums tend not to be mite resistant. Mite resistant Geraniums, such as: 

  • Double Lilac White
  • Madame Margot
  • Salmon Queen
  • Amethyst
  • Sunset

… tend to also be edema resistant. 

How Can You Prevent & Treat Geranium Edema? 

As with most plant problems, overwatering is the main culprit in developing Geranium edema. To prevent this problem: 

  • Make sure your Geraniums are planted in a very fast-draining soil mix. Amend the soil in the landscape with fine gravel, coarse sand, and light organic compost. Consider planting potted Geraniums in a soilless potting mixture.
  • Use the soak and dry watering method. First, water thoroughly, allowing the water to run through the planting medium. Do not water again until the substrate is dry and/or the plant shows a bit of wilting. Never allow potted Geraniums to sit in water.
  • Never mist Geraniums, and don’t use overhead watering methods. Keep the leaves dry if possible.
  • Indoors, keep humidity levels low around Geraniums. You may need to raise the temperature in the area where Geraniums grow.
  • Keep soil temperatures around 65° degrees Fahrenheit. Air temperatures should be around 70°-75° degrees Fahrenheit.
  • Evaluate the soil’s pH level on a regular basis because Geraniums tend to cause the pH levels of their soil to drop. A slightly acidic at a 5.5 level. 

How Can You Control The Environment Of Outdoor Geraniums? 

For Geraniums planted in the landscape, there may not be much you can do if the weather works against you. Good stewardship can help, though. 

Just be sure to plant your Geraniums in an area (and using a soil mixture) that provides excellent drainage. 

Pay attention to the pH level and condition of your soil. Then, amend it as needed to provide the right acidity levels and proper nourishment.

Don’t crowd your plants close together. When you plant them, be sure to leave plenty of room for good air circulation. 

Prune away damaged foliage, and prune your Geraniums judiciously to help improve air circulation around the leaves. 

Don’t water during cool, wet weather, or humid weather. 

Geraniums Can Recover From Edema

Edema affects all sorts of plants, and it is relatively easy to treat it successfully. Since it is caused mainly by environmental conditions, taking steps to correct the problems that cause it should yield positive results. 

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