How to Lay the Groundwork for "Gleam"
Before you try to add a little extra gleam to your ficus or grape ivy, first you need to remove the dust that is dulling the foliage. It's easy to forget that a plant needs to breathe and admit sunlight. Too much dust, and it won't be able to perform these vital functions. Some plants may look “faded” simply because they need their leaves freed up to take in more air and light. Here’s how to do that:
If your houseplants are portable, wrap plastic wrap around the base of the plant, to cover the earth in the pot and prevent overwatering and earth runoff. Next, get your shower running at a gentle spray of water, between lukewarm and cold, and refresh your little friends with a cleansing shower. Turn them around to cleanse them from all angles.
If the plants aren't portable, try spraying them with a bottle of water. Forceful squirts can knock off dust. (You may want to cover the floor around them with a plastic tarp to protect it during this procedure.) Spray the undersides of the leaves as well as the tops.
Alternatively, you can use a cottonball, sponge or soft cloth dipped in a mild detergent solution (one drop of detergent in sixteen oz. of water). Rinse off all traces of the detergent with clear water. Or, you can dust your plants with an electrostatic duster.
Now "Go for Glow"
Check how your plants look when they're dry, if they look healthy and happy, this water refresher may be all the polish they need.
If you want to go for a more glossy look, you can dip a soft clean cloth in a tiny bit of mayonnaise or a drop of vegetable oil and rub this onto the tops of the plants' leaves. Buff them lightly. This also will wipe off any excess oil or mayonnaise. Polish only the tops of leaves so that the pores on the underside through which the plant breathes are left to do their vital work.
Whatever you do, do not use furniture polish or cooking spray. You may get temporary “great results” but this will smother your plants.