(Question)
I left a bag of potting soil in the sun for a month. When I opened it there was mold on the soil. Is it still safe to use the soil for houseplants?
(Answer)
Thank you for contacting the Toronto Master Gardeners.
Mold in bags of potting soil appear when the bag is warm and moist inside and there is no air circulation. It is really proof of life in the potting soil and that it will provide an active root environment. Once the bag is opened, sunlight and drier air will cause the mold to die off. Then the potting soil can be used either inside or out.