Direct vs. Indirect Light on Plant Growth

Direct and Indirect Lighting

• Indirect lighting does not refer to filtered light, such as what streams through your glass windows, but reflected light. Indirect lighting can be light reflected from the sun or from a bulb. A mirror or similar reflective object is used to point indirect lighting toward plants. Direct lighting is non-reflected light from the sun or from electric bulbs. Even light shining through a window is considered to be direct lighting, so long as it is not bouncing off a reflective surface before it reaches the plant.

Effect on Plants

• Some plants are sensitive to direct sunlight. The leaves and flowers may become scorched when light is too strong. Plants that should have indirect light include African violets, azaleas, gloxinias and orchids. Sun-loving plants that need direct light to thrive include cyclamens, geraniums and sunflowers. Too much light can be just as damaging to plants as too little.

Symptoms of Improper Lighting

• When plants are receiving too little light, the foliage will turn yellow and wilt. As the plant fails to receive enough nutrients to nourish its leaves, the foliage will drop. Growth may look thin or leggy, and leaves may be stunted or smaller in size than normal. Buds and flowers may not form at all when plants aren't receiving enough light. Plants that are getting too much light will also begin to look discolored. The leaves will appear whitish or pale, almost bleached in appearance, and when flowers appear they may be paler in color than normal or brown and scorched.

Finding the Light

• Light is different on all four sides of your home. Windows that face the north provide the smallest amount of light. Place shade-loving plants that require very little light in the north-facing windows of the home. Windows that face east are a natural source of indirect light and cool temperatures. On the southern side of the house, the windows let in large amounts of light. Plants that want bright, direct light will flourish in southern-facing windows. Windows that face west give plants a little bit of both: in the morning, indirect light shines through; in the afternoon, direct light is provided through the window.