Answer: In some cases moss indicates some sort of soil imbalance such as extreme acidity, although it would be somewhat unusual to find that in a typical potting soil. Other causes for moss would be poor drainage or possibly more likely, compacted soil with low fertility levels. You might want to refresh the soil by at least a third to a half of its volume each year and add some good compost to it to try to remedy the situation. On the other hand, if your plants seem to grow well, the moss is not necessarily a problem.
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