Answer: In my experience an occasional watering with the dregs from a cup of tea or coffee had no discernible effect on houseplants. It is possible that it might acidify the soil somewhat but that would be leached away during normal watering. In some cases herbal teas have been ascribed special properties such as chamomile may serve to counteract the effects of damping off on seedlings. I suppose the answer to your question would depend on the type of tea and method of application.
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