A1483
How to grow African violets
Y H.C. Harrison, M.F. Heimann, and P.J. Pellitteri
ou can grow African violets successfully in your home if you provide moisture, temperature, and light conditions similar to those under which the plants grow naturally. This isn’t as difficult as you may think, even though the African violet comes from the coastal and mountain regions of East Africa. There the temperatures average 70˚–80˚F and never go below 50˚F or above 100˚F. The plants flower profusely in the moist air and rich soil of shaded, rocky areas. In homes we can control heat, light, and moisture to give our African violets “natural” growing conditions.
Soil and fertilizer
African violets thrive in a fertile, porous, well- drained soil. For a good soil, mix one part coarse sand or perlite, 2–3 parts loamy soil, and three parts organic matter—peat moss or compost. With heavy garden soils that contain a high percentage of clay or silt, mix in more organic matter and perlite or sand. Many garden soils contain insects and disease organisms; therefore, sterilize the potting soil mixture to kill insects or diseases that might hurt your plants. Commercial mixes are usually sterilized, and this information is printed on the bag. To sterilize your own potting mix, moisten it slightly, place it in a heat proof container, and heat it to 160˚–180˚F in your oven. Maintain this temperature for 45 minutes. This procedure improves the physical structure in addition to destroying insects, diseases, and weed seeds.
Add 1⁄2 teaspoon of superphosphate (0-20-0) fertilizer per quart of sterilized potting soil when you pot violets. Your plants shouldn’t require any more fertilizer for at least 6–10 weeks. After that, give your plants a liquid feeding of a complete commercial fertilizer once or twice a month. Follow the manufacturer’s directions for African violets or about one-half the rate recommended for most other indoor plants; apply as much liquid as you would in a regular watering. Be careful not to get any liquid on the leaves because the solution will burn them. Liquid feeding is most important during and just after flowering. Failure to maintain adequate nutrient levels often leads to poor flowering.
Potting
Check soil moisture before potting young plants and repotting older ones. The mix should pack slightly when you squeeze it. If you use pots that are 4 inches or more in diameter, put a piece of broken clay pot—concave side down—over the drain holes. This ensures that excess water drains easily from the pot. If the soil is too wet, roots suffer because they don’t get enough oxygen. African violets are often potted in rather shallow, wide containers. Repot when you notice excessive loss of lower leaves and development of a long “neck.” If you have to water violets frequently, they are probably root or pot bound and should be repotted.
H O W TO
G R O W
A F R I C A N V I O L E T S
Pot the plant with the crown just slightly above the soil line. If planted below the soil line, the crown may rot rapidly. Immediately after planting, water the soil thoroughly from above to establish good contact between the roots and soil.
the wick up through the drainage hole. Unravel this end and spread it out over the base of the pot. Then fill the container with soil and pot your plant. Then put the wick’s free end in a container of water. Capillary action will carry water up through the soil.
If you use a south or west window, make sure it is shaded during bright sunny days. If no trees, shrubs, or curtains shade the window, move the plants away from a south or west window when it receives intense summer sun.
African violets grow and bloom better if you repot them about once a year. When repotting, remove some of the surface soil and soil from the surface of the root ball and replace it with a good soil mix.
If you are watering from below or with wicks, salts may gather near the soil surface and injure leaf stalks (petioles). A thorough monthly watering from above will wash these salts down and out of the soil.
Turn your plants weekly to encourage even growth on all sides.
Water
African violets grow best in a soil that is moderately moist at all times. This does not mean you need to water daily—only when the soil surface is dry to the touch. Then water thoroughly with room temperature water, wetting the entire soil ball. Avoid overwatering or keeping the soil saturated; overwatering often kills plants.
Light
Your African violets will grow and bloom better if they get the right You can water violets from above or amount of light. Plants won’t flower below. To water from above, pour the water onto the soil until water runs out with too much or too little light. They do best in a well-lighted location that the drain holes. Remove excess water doesn’t get direct sunlight during from the saucer. If you use containers noon or afternoon hours. Usually without drain holes, water plants carefully to prevent overwatering and a north or east window with no shrubbery, trees, or curtains shading it, yet maintain a moderately moist soil. gives good light for your plants. To water from below, set the container in an inch or more of water. Water will seep up through the soil. When the soil surface becomes moist, take the container from the water and let it drain. Use different water for each plant to keep nematodes and other pests from spreading from plant to plant. If your African violets are in glazed or plastic containers, water from above unless you use the wick system, because water cannot pass through the walls of these containers. Use wicks of nylon or glass fibers. Take an empty pot and pull one end of
You can grow excellent African violets under artificial lighting. Two 4-foot, 40watt fluorescent tubes (standard cool white) and a reflector provide the right amount of light for 8 square feet of area. Suspend the tubes a foot above the plants and leave the lights on 18 hours a day for best results.
Temperature
African violets grow best with daytime temperatures of 70˚–72˚F and a night temperature around 65˚F. Night temperatures below 65˚F produce malformed and discolored plants. Leaves curl under and become brittle when exposed to prolonged cold temperatures. In winter, protecting plants near windows from cold drafts is especially important.
Humidity
Fairly high humidities are best for African violets. In winter the air in most homes isn’t moist enough for these plants. A good way to increase the
U N I V E R S I T Y
humidity near plants is to put the pots in shallow trays that have an inch or two of fine gravel in the bottom. Keep water in the trays almost to the top of the gravel. This water evaporates into the surrounding air, giving your plants a favorable atmosphere.
Starting new plants
Starting new African violets is easy with leaf cuttings. Select a healthy, recently matured leaf and remove it from the violet’s crown, leaving no stub. Cut off all but 11⁄2 inches of leaf stalk. To root the leaf, put it in water, sand, vermiculite, or a 50-50 mixture of perlite and peat moss. If you root leaf cuttings in water, place a piece of wax paper or plastic wrap over the container’s top and fasten it down with a rubber band. Slip the stalk of the cutting through a hole in the wax paper and into the water. You can add a small piece of activated charcoal to keep the water “pure.” In 2–4 weeks roots will form on the leaf stalk’s cut surface. When roots are 1⁄2- to 1-inch long, plant the cutting in a mixture of perlite or sand and peat moss. Shallow planting lets the young plants develop quickly. When new leaves start to develop, pot the cutting in the soil mixture described earlier. If you root your cuttings in sand, vermiculite, or a combination of sand and peat moss or perlite, plant leaf stalks one inch or less deep and keep the cuttings out of direct sunlight. The leaf blade should not touch the soil surface. Give them plenty of water. When new leaves start growing, transplant rooted cuttings
to potting soil. New plants from leaf cuttings often take 6–12 months before flowering. Older plants frequently develop several crowns. With a sharp knife you can easily separate crowns with some roots still attached. Pot the separated crowns in the recommended soil mixture and water the soil thoroughly. This is a quick method of starting new plants. Old plants flower and look better if they don’t have too many crowns.
O F W I S CO N S I N - E X T E N S I O N
• Leaf stalks rot where they rub against the pot’s edge. Cause: High salt concentrations on the side of the pot and near the soil surface damage leaf stalks allowing the Botrytis fungus to enter. Protect leaf stalks with a strip of aluminum foil, paraffin, or a cardboard cover around the pot’s rim. • Plants don’t bloom. Causes: Too much or too little light; low temperatures; overfertilized soil; stove gas in the air; too much or too little water.
Solving African violet Diseases troubles Powdery mildew is a grayish-white, Spotted leaves. Causes: Watering with cool water; use only room temperature water. Water droplets on leaves in full sun may also cause spotting because these leaves are very warm. • Compact plants and pale yellow leaves. Causes: Too much light and inadequate fertilization. • Compact plants and few or small blooms. Cause: Not enough light.
powdery growth on leaves, stems, and occasionally on flowers. It is sometimes confused with mealybug infestation. You can get rid of powdery mildew by treating plants with a labeled powdery mildew fungicide. Two or three applications may be necessary. If you spray the plants, make sure you thoroughly wet the foliage with the spray. Adding a commercial wetting agent or a small amount of liquid household detergent helps. Keep plants spaced far enough apart to allow for air circulation.
• Buds dry up. Causes: Not enough moisture in the Botrytis blight causes discolored and air or soil, and temperatures that are water- soaked flowers. To prevent too high. it, reduce high humidity. To stop • Leaves curl downward. the disease, spray or dust with an Cause: Low temperatures. • Sudden plant wilting and crown rot. Causes: Overwatering or root and crown rot. You may be watering too often, drainage may be poor, or the plants may be set too deep in the soil. The root system may be infested with a pest.
H O W TO
G R O W
A F R I C A N V I O L E T S
appropriate fungicide. As with powdery mildew, it is important to provide air space between plants. Stem rot is a likely suspect if leaf stalks are rotting near the crown and the plant still has a healthy root system. Cyclamen mites may be spreading the disease. Always use sterilized or pathogen-free soil. Root rot is usually caused by a “water mold” fungus. You usually can’t save diseased plants. To avoid spreading the disease, use clean soil, isolate suspect plants when you first notice them, and follow the techniques mentioned above to prevent overwatering. To help control any of these diseases, do not allow water to stand in the saucer after the plant has taken up all it needs.
Insects
Cyclamen mites are microscopic pests that cause young leaves to be thick, hairy, deformed, brownish green, and to cup downward. Treat with an insecticidal soap or a miticide according to label instructions. Isolate infested plants. Heavily infested plants should be destroyed to protect uninfested plants.
When using pesticides, follow directions on the manufacturer’s label. Failure to do so violates the law.
Mealybugs look like cottony deposits on leaves and stems. To kill these insects, spray with an insecticidal soap. To protect plants from mealybugs, forcefully spray the plants with room temperature water once a week. Aphids cause distorted young growth and deformed flowers. You can see these tiny insects feeding on tender plant parts. Control is the same as for mealybugs. Springtails (“jumping insects”) may appear in saucers or at the soil surface after watering. They are an annoyance, but won’t hurt plants. To help control springtails, repot your plant into a sterilized soil media. Fungus gnats are frequently mistaken for fruit flies, but have more delicate wings and slender bodies. They are a nuisance as they hover around moist soil, but won’t usually harm your plants. Use a sterilized soil mix and allow the soil to dry out moderately between waterings to control this pest. A note about insecticides. Many formulations of insecticides are not registered for use on house plants. Some formulations may be mixed in solvents or carriers that burn African violets. Before using any insecticide, check to be sure that African violets and your specific pest problem are
listed. Always follow label instructions when mixing and applying insecticides.
Nematodes
Nematodes reduce plant growth and cause swollen, gnarled roots. Treating infected plants is difficult and not recommended for amateurs. Prevent the problem by using nematode-free plants and soil. Commercial African violet soil is free of nematodes. You can kill nematodes in soil, on containers (except plastic), and on tools by steamsterilizing them or heating them in the oven at 180˚F for 30 minutes. Avoid splashing infested soil while watering, which can spread nematodes from diseased to healthy plants. In many instances, you should discard nematode- infested plants as soon as you detect them. If they are valuable plants, you may want to keep them until you take some healthy cuttings. To take clean cuttings from infected plants, carefully remove leaves with a clean knife and avoid touching the soil. Until you have a chance to take the cuttings, isolate infested plants from healthy plants, and avoid the possibility of spreading nematodes through infested soil.
Copyright © 2014 by the Board of Regents of the University of Wisconsin System doing business as the division of Cooperative Extension of the University of Wisconsin-Extension. All rights reserved. Authors: H.C. Harrison is a retired professor of horticulture, M.F. Heimann is a retired outreach specialist of plant pathology, and P.J. Pellitteri is a retired outreach specialist of entomology, College of Agricultural and Life Sciences, University of Wisconsin-Extension and University of Wisconsin-Madison. Thanks to L.M. Berninger, G.E. Beck, G.L. Worf, and D.L. Mahr for their work on earlier editions of this publication. Updated in 2014 by Johanna Oosterwyk, D.C. Smith Greenhouse Manager. Cooperative Extension publications are subject to peer review. University of Wisconsin-Extension, Cooperative Extension, in cooperation with the U.S. Department of Agriculture and Wisconsin counties, publishes this information to further the purpose of the May 8 and June 30, 1914, Acts of Congress. An EEO/AA employer, the University of Wisconsin-Extension, Cooperative Extension provides equal opportunities in employment and programming, including Title IX and ADA requirements. If you have a disability and require this information in an alternative format, or if you would like to submit a copyright request, please contact Cooperative Extension Publishing at 432 N. Lake St., Rm. 227, Madison, WI 53706;
[email protected]; or (608) 263-2770 (711 for Relay). This publication is available from your county UW-Extension office (yourcountyextensionoffice.org) or from Cooperative Extension Publishing. To order, call toll-free 1-877-947-7827 or visit our website at learningstore.uwex.edu.
How to Grow African Violets (A1483)R-09-2014
