Reflecting sunlight or indirect light can be done by changing the color or material surrounding a plant either indoors or out. While reflection of direct sunrays outdoors often causes undesired increases in heat or leaf scalding, indoor use of mirrors, and light-colored wall or table coverings gently and effectively direct light rays to houseplant foliage.
Indoor Light Manipulation
Place a large mirror under the potted house plant. The mirror should be at least 5 to 10 inches larger in diameter than the plant container that rests upon it.
Monitor the foliage of the houseplant, watching for scalding of leaves from intensified, reflected light from the mirror. Leaf scalding looks like a metallic sheen on a leaf or a tanning/bleaching of green tissues. Shift the location of the mirror and plant in the room slightly to decrease the sunlight reflection, duration or intensity upon the plant.
Place the mirror or a large piece of white poster board on the wall behind a houseplant so that the window light is reflected to the back side of the plant. This is especially helpful for plants in the rear of a room that appreciate low to medium light levels.
Paint walls white or a lighter shade to better reflect indirect light around the room, often to the benefit of foliage plants.
Outdoor Sun Reflection
Paint adjacent building facades and foundations white or a light shade of gray or silver.
Cover the soil around the plant with a layer of white plastic. Keep the edge of plastic at least 6 inches away from the plant base to facilitate watering and air exchange for the roots in the soil. Alternatively, a light-colored mulch can be used to layer the ground to improve light reflection on dark-colored soil.
Position matte-finish sheets of metal, like tin or aluminum, around the plant at an angle to refocus light. Do not place the metal sheets too closely to the plant, as the heat from the sun-baked metal can dehydrate the plant foliage.