yellow leaves geranium geranium can be caused by any number of issues, but the good news is that most are easy to fix. For example, if you see that your geraniums are discolored as they approach dormancy in the fall or early spring when they’re coming out of their winter hiatus, this is normal and just part of the plant’s natural life cycle. Additionally, prolonged cool and wet weather can also cause a tinge of yellow to the foliage of hardy geraniums or pelargoniums as they transition from one season to another.
If you’re growing your geraniums in containers, the problem is often caused by poor drainage. This can be easily solved by using a potting soil that drains well, or by incorporating some grit and organic material into the potting mix. These ingredients allow for some tiny air pockets and prevent the potting medium from becoming compacted.
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Alternatively, the yellowing may be caused by overwatering. Water your geraniums only when the top 1″ of soil feels dry to the touch, and always from below so that the water can reach the root ball. Watering too frequently can risk the spread of a fungal disease called Bacterial Leaf Spot, which manifests as yellow spots on the leaves.
Lastly, the yellowing of geraniums can also be a sign of an imbalance of essential nutrients. A common nutrient deficiency is magnesium, which is required for photosynthesis. Ensure that your potting soil contains this mineral and that you’re using a fertilizer that contains it or use a magnesium supplement such as Epsom salts (the chemical name for which is magnesium sulfate heptahydrate). This will help to provide the green pigment your geranium needs.
