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Dust and hard water can leave deposits that slow photosynthesis, but don’t believe everything you read about using acids to remove them
The problem
Dusty leaves are more than a cosmetic problem. A film of dust blocks light, which slows photosynthesis and dulls the plant. Hard water makes it worse, leaving chalky white mineral spots on the foliage that a damp cloth simply smears around.
The hack
The acids in white vinegar, or lemon juice, dissolve the mineral salts left behind by hard water – just wipe a very diluted solution over the leaves with a microfibre cloth.