Don't shrink away from African violets as houseplants
PATSY BOWMAN
Hints And Tips From One Of Hopkins County's Master Gardeners

January 2, 2004 -- The African violet (Saintpaulia) is an excellent flowering house plant which will grow and flower under low light intensities found in the average home. Where there is insufficient natural light, they can be grown and flowered successfully entirely under artificial light. Large numbers of different varieties, types and colors available, and the ease with which they can be propagated make this an excellent plant for interior decoration of the home.

African violets require about 1,000 foot-candles of light for 8 to 12 hours per day for best growth and flowering. Excessive light levels cause leaves to be pale or yellowish green, much lighter than normal and some leaves may show dark areas where they have been shaded by other leaves. Growth at high light levels is slowed and plants become more compact, however, although flowering may continue freely for a while it will eventually decrease due to chlorophyll destruction.

The length of time plants are exposed to light also affects growth and flowering. African violets should not be exposed to direct sunlight. African violets can be successfully grown when the only source of light is from fluorescent lamps, which give better results, are less expensive to operate, and produce less heat. This light can be provided by suspending two 40-watt fluorescent tubes 12 to 15 inches above plants. Tubes should be mounted in suitable fixtures equipped with reflectors.

African violets grow best at a night temperature of 65 to 70 degrees, but will grow satisfactorily at 60 to 80 degrees. African violets tolerate dry air, but need higher humidity for best growth and flowering. Humidity around plants can be increased by setting pots in water-tight metal or plastic trays filled with wet pebbles or sand. Care must be taken to avoid placing pots directly in water to prevent root damage.

Drainage is one of the most important considerations in preparing a soil mixture for African violets. An excellent mixture of readily available materials may be prepared by mixing equal parts (by volume) of soil, sphagnum peat, and horticultural grade perlite. Excellent plants can also be grown in mixtures consisting of equal parts of sphagnum peat moss and perlite. Commercially prepared packaged soil mixtures are also available for African violets. Soil mixtures should have a pH of about 6.0 to 6.5 or be slightly acid for best results.

A definite schedule for watering African violets is not desirable since frequency and amount of water required varies with soil mixture, drainage, light, temperature and humidity under which plants are grown. Some types of pots, such as clay pots, require more frequent watering than those in plastic pots since evaporation is greater. Decorative glazed pots without drainage holes are generally unsatisfactory due to lack of drainage.

In general, water should be applied whenever the surface soil feels dry to the touch, but before it becomes hard or the plant wilts. African violets may be watered from the top or bottom. When watering from the top, apply sufficient water to surface soil to thoroughly saturate it and discard excess water which drains through the bottom of the pot. Watering from the bottom may be done by placing the pot in a container to which about 1 inch water is added. When the soil surface becomes moist, remove the pot and pour out excess water.

Temperature of the water should be room temperature or slightly warmer to avoid any chance of spotting leaves if water contacts foliage. Use of chlorinated or fluorinated water is satisfactory.

Use a water-soluble fertilizer containing nitrogen, phosphorus, potassium and other required nutrients specifically sold for African violets. This container will state how often to fertilize.

African violets may be propagated easily by leaf cutting, and about 60 to 9 months are required to obtain flowering plants. Any leaf is satisfactory if healthy and firm. Remove the entire leaf with petiole (leaf stem) by snapping or cutting it off at the stem of the plant and trim the petiole to about one inch in length. A combination of half vermiculite and half sand, by volume, makes an ideal propagating medium or the soil used for growing plants may be used. Insert the petiole into the medium by pushing it into a hole made with a pencil or similar tool. Roots normally appear at the petiole base in three to four weeks under good conditions and leaves of the new plants appear at the medium surface three to four weeks after root formation.

New plants brought into the home should be examined thoroughly for signs of insects and diseases. Control of most insects and mites can be obtained with insecticidal soap sprays. Mealy bugs may be controlled by mixing alcohol with an equal amount of water and touching each insect with a cotton swab dipped in the solution. Various disease organisms may affect African violets from time to time, but adequate spacing of plants, use of sterilized soil, provision for good air circulation, prompt removal of faded flowers and unhealthy leaves, and control of thrips and mites are all important preventative measures. Once a flower or leaf disease is noticed, spraying with captan or mancozeb will often aid in controlling the disease. Read and follow all label directions when applying a fungicide to African violets.

Root diseases usually result from over watering of plants. Symptoms may not show up on the leaves until severe root damage has occurred. In most cases with root diseases or damage the best control is to discard the plant and purchase new healthy ones.

Other problems: cold water touching warm leaves can cause yellowish rings, spots or streaks on the upper surface of leaves. Petiole rot occurs when petioles touch the edge of the pot and develop brown, sunken areas at points of contact. The injury is localized and does not cause the petiole to rot unless disease organisms enter the wound. This trouble is the result of chemical injury caused by the accumulation of soluble salts at the pot rim of clay pots. This problem can be reduced by using fertilizers sparingly and applying sufficient water to thoroughly saturate the soil. When water is applied to the soil surface, excess water and the salts will drain out the bottom of the pot. Petiole rot can also be avoided by waxing the pot rim or covering it with aluminum foil.

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