Answer: In my experience, the moss serves two functions, insulating the roots from excess heat and making the exterior of the basket look good. In hot summer areas such as yours, it is better to line the basket with the moss so it looks good, then use a layer of plastic to line the moss, then add potting soil. Be sure to poke a few holes in the plastic to allow excess water to drain out. In cooler summer areas where evaporation is not such a problem, some people skip the plastic layer.
It can help make the moss more pliable if you wet it before use. If you are using it without the plastic, it is very important to keep the moss damp so it does not wick moisture away from the soil and plant roots.
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