Issue: January 27, 2007
African violet light and salt problems
Question:
I have an African violet and questions about it? Mine is growing well but the stems are growing long. It also has several leaves with brown edges. I have it under a plant light in a well bowl.
Victoria S.
Answer:
As I read your question, I wonder what you are describing as "stems". You write of your African violet in the singular, but talk of stems as plural. I think what you are calling stems are actually leaf petioles. The petiole is the part of the leaf (the stalk) that attaches the leaf blade to the true stem. When the African violet does not receive adequate light, these petioles elongate. The result is a small leaf at the end of a long petiole. In this situation the plant produces few blossoms, if it blooms at all.Ê
If it is indeed the petioles that are elongated, rather than the stem that grows from the potting soil, then the problem is probably that the plant is not receiving enough light. The solution to the problem is to give your plant brighter light.
The African violet plant is capable of growing in surprisingly low levels of light, but it does not prosper and produce flowers. Plant grow lights are not always adequate. It depends on the type of lamp (incandescent or fluorescent), the number of lamps, and the plant's distance from the lamp. Incandescent plant lamps generate too much heat to place them close to the plant. They are often used to supplement sunlight, but not replace it. You need to increase the intensity of sunlight that the plant receives. Don't move it quickly to a window, rather move it closer to the window, but not into direct sunlight. Sheer curtains over a window will protect the plant from direct sunlight and provide good lighting conditions for the African violet. A north-facing window usually does not provide adequate light, but east-, south-, or west-facing windows will work well.
Fluorescent lamps are cooler and can be placed closer to the plant.Ê African violets will often grow and bloom under two fluorescent tubes suspended about 4 inches above the plant. Sunlight is not needed in this case. However, the light intensity decreases with the square of the distance from the lamps. If you double the distance between the lamps and the plant, you don't reduce the light to one-half, you reduce it to one-fourth what it received when it was twice as close to the lamp. If your grow light is fluorescent, move the plant closer to the lamps (at least two fluorescent tubes). As the lamps age their light dims (you eyes will not be able to detect this) and you will need to replace the lamps.
The brown edges of the leaves probably indicate salt accumulation in the potting soil. As we water, the salts (calcium and other salts) dissolved in water accumulate in the potting soil. The solution to this problem is to repot the African violet in fresh, high-quality, potting soil. Gently wash away as much old soil as possible from the roots when you repot. After removing as much soil as possible, repot in fresh soil in a clean flower pot. Apply water to settle the soil around the roots, but take care not to water excessively.
The "well bowl" that you described may contribute to the problem if you allow water to soak the soil from the bottom when you water. Bottom watering hastens the accumulation of salts in the soil, especially when applying water from most New Mexico water sources. Water so that surplus water carries salts from the potting soil and that water can then be discarded, not soaked back into the potting soil.
Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.
For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.
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