I do not own a greenhouse and my plants are kept indoors however I do as best as I can to mimic the conditions in their natural habitat. I'd like to have a go at growing a couple of plants that require slightly higher humidity than what I currently provide and have learned that putting gravel in the plant's water tray will aid in increasing humidity.
Naturally, I'm curious about this, even more naturally I don't want to try this method out without hearing from some of the professionals. I'd like to know if this method works (I know some line the floor of their greenhouse with gravel to increase humidity) and what gravel would be safe to use (considering it will be in the water tray, I don't want minerals to leak into the water). I would love to try some of the more challenging carnivorous plants available in the future (when I have more experience) and I'm aware some of these plants require higher humidity. I'd also like to consider using this method for my nepenthes.
List of online carnivorous plant suppliers