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Small droplets appearing along a houseplant's leaf edges aren't always dew.
Plants can release liquid water through specialized structures in a process called guttation. It commonly occurs when soil moisture is high and conditions reduce normal water loss through transpiration.
The droplets can sometimes leave mineral residue behind after evaporating.
A plant can therefore appear to have tiny drops of water on its leaves even though nobody sprayed it and no rain entered the room.
© Royal Horticultural Society