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Index : Plant Care
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- 26. Low Light can Cause Plant Problems - Top
- Believe it or not, even in Arizona, lack of sunlight can cause plant problems. This can occur in late Autumn and into the Winter, as our days shorten and the sun continues to sink lower into the southern skies. The reduced number of daylight hours and lower sun intensity can cause problems as some sun-loving plants may not receive all the light they need to grow and flower properly.
House plants are most commonly effected by reductions in light levels. Plants growing in north-facing windows or those in room interiors far away from windows may become light deficient. The first indication may be a yellowing or dropping of leaves throughout the plant. Plants craving light often stretch out for it creating long, spindly growth. Usually compact plants become thin and leggy, developing long spaces between leaves. Flowering plants cease flowering. As conditions worsen, plants become stunted and simply stop growing!
It will be necessary to relocate high light requiring plants such as hibiscus, jade plant, asparagus fern, hoya, schefflera and others. Moving them to east-facing windows, or closer to west and south-facing windows will provide additional light. Be careful not to place plants in locations exposed to strong direct sun-light. This can cause plants to sun-scorch or wilt from excessive heat build-up.
Placing house plants near an artificial light source during the evening hours can also be used to increase light exposure. Plants can be placed close to fluorescent lights. However, keep them back a foot or so from incandescent bulbs as they can be damaged by the heat produced by these bulbs. When starting garden seedlings indoors use a combination of one cool white and one warm white fluorescent tube in a single fixture, such as a utility lamp. This combination provides the best reproduction of natural sunlight.
Just as plants indoors may not be receiving enough light in north exposures, the same holds true for container plants on north-facing patios. Sun-loving flowering plants such as geranium, petunia, snapdragon, calendula, and stock will have sparse blooms or cease flowering altogether in deep shade. When possible, relocate container plants to areas receiving at least 6 hours of direct sunlight per day. Just moving pots farther out from the house, away from the heavy shade created by north-facing house walls and overhangs will help. Longer periods of brighter indirect light can compensate for the lack of direct sunlight.
Evergreen trees casting too much shade on patio plants and winter flower or vegetable beds can be pruned to thin growth and allow more sunlight through. Thinning is the selective removal of stems and branches throughout the tree's canopy. Cuts should always be made at the point were the branch to be removed intersects with another branch or the main trunk. Wait until mid-December to prune! Pruning while temperatures are still warm can stimulate new growth that is cold sensitive and easily damaged by frost and freezing temperatures.
Do not prune citrus trees to thin growth! The bark of citrus trees are sensitive to light. Exposing the trunk and branches to strong sunlight can cause the wood to sun scald and die.
When planting vegetable and flower beds, always locate taller growing plants on the north side so that they do not block sun from lower growing varieties. Some flowers are adapted to shade conditions and will bloom well. They include; pansies, impatiens, begonias, and coleus. Plant these when shade conditions cannot be avoided. Many cool season vegetables also tolerant at least partial shade. They include; lettuce, green onions, leeks, kale, cabbage, carrots, beets, radishes, Swiss chard, and turnips.
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Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona, 520-626-5161.
Material originally appeared in Arizona Daily Star gardening column, on November 21, 1999
- Updated: November 21, 1999
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