Dusting and regular house cleaning chores keep this layer removed from furniture but we often fail to realize that plant leaves are no different from a tabletop when it comes to holding a layer of dust. Such a layer of dust on the leaf can be harmful at this time of year when light levels for the plant are lower than desirable. The added barrier to light penetration reduces the plants ability of absorb what light is available and tends to put it under further seasonal stress. Dust can be easily removed from large-leaved plants with a soft cloth that is either dry or slightly damp. Don't put too much pressure on the leaf since they are easily bruised.
Washing helps remove the dust on plants that are small enough to be moved to a sink or tub.
Adjust the water so it is warmed slightly above the natural temperature for this time of year. Water from the cold tap can be far too cold for plant foliage. Be careful not to cook the leaves either. This is also a good time to flush the growing medium of unwanted salts that have collected when water evaporates from the soil surface. Allow it to drain and return your cleaned plant to its previous location.