Plant Light: Home Plants Signal Light Problems

Any plant not getting enough light will be quick to show us the symptoms of its ailment. One of the first signs of poor light is new growth that develops as stretched-out, spindly shoots. The leaves on these spindly shoots may be undersized and often somewhat cupped or curled. Plants that were receiving enough light, but then were abruptly moved to a location with poor light may develop yellow leaves that soon drop. Leaf drop often is accompanied by reduced growth and eventually no growth at all, while plants that normally have variegated leaves produce leaves with less or no variegation.

If low light persists, plants showing these symptoms may eventually die. Others may continue to drop leaves or produce leaves with blackened tips or margins, which finally die and drop off. Plants in poor light require less water than the same plants growing in better light. They also need little or no fertilization since growth is slow. Extra water and fertilizer are not substitutes for poor light and can do more harm than good. Even though a plant is located near a window, it may still not be getting enough light.

Light may be reduced greatly by shade trees, buildings, curtains, balconies or overhanging roofs. Southern exposures normally provide the brightest exposures while northern exposures provide the least outdoor light. Plants are divided into three general light need categories: low light (50 to 500 foot candles), medium light (500 to 3,000 foot candles) and high light (3,000 to 8,000 foot candles). Low light areas generally exist more than 10 feet from a window, unless the window is large, light is too low for even low light plants to grow well beyond this distance.

Medium light intensities exist close to windows, but to the side of them where there is no direct sunlight. Plants grouped in the high light category need to be close to windows and should receive some direct sunlight each day.

While we are usually concerned with insufficient light, too much light may cause damage also. The damage is a condition known as sun scorch. It is most often seen on plants that have been growing indoors that are abruptly moved to direct sunlight outdoors. It may also appear when plants in poor light are moved to a sunny window in late spring or summer. Both bright light and high leaf temperatures that accompany it cause the damage.

Sun scorch causes faded, yellow leaves. Eventually dead areas develop in the bleached spots. It normally appears most on upper, exposed leaves. Damaged leaves should be removed after normal leaves begin to develop. Any relocation of house plants to different light source should always be done gradually.