Caring
for African Violets
African violets are low, compact plants with
attractive dark green, thick, hairy leaves.
This NebGuide covers various aspects of caring for them.
Donald H. Steinegger, Extension Horticulturist
John Watkins, Extension Plant Pathologist
Anne Vidaver, Head, Department of Plant Pathology
Frederick P. Baxendale, Extension Entomologist
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The African violet (Saintpaulia ionantha) is one of the most
satisfactory flowering houseplants. It is a low, compact plant with
attractive dark green, thick, hairy leaves. The violet-like flowers are
borne in small panicles just above the foliage. Besides various shades
of blue-violet, there are also pink, fuschia, and white cultivars
(varieties). Newer violets include not only cultivars with single
flowers, but also those with semi-double or double rows of petals.
Bi-colored flowers and those with a contrasting border are popular.
Trailing cultivars and miniatures are also available. Plants kept in
good condition flower almost continuously.
A soil mixture composed of about 2 parts fertile loam, 1 part leaf mold
or peat, and 1 part sand or perlite is recommended for growing African
violets. The soil must be porous to allow surplus water to pass through
readily. Most violets are now grown in a pasteurized soilless mix. A
good soilless mix is made up of 3 parts sphagnum peat moss, 2 parts
vermiculite, and 1 part perlite, with some lime added to balance the
acidity of the peat moss. Compost, good garden soil, or loam can be used
for up to half of the total mix, with the other half being vermiculite
and/or perlite. Such a soil mix is very porous. A good growing medium
should contain 50 percent matter, 25 percent air, and 25 percent water.
When potting African violets, take care to set the plant so that the
crown is just above the surface and the soil is firmly pressed around
it. Emphasis should be on good soil drainage because free water on the
surface may cause decay at the crown or at the bases of the leaf stalks.
A saturated soil mix also leads to unthrifty top growth and root rots. A
layer of coarse gravel at the bottom of the container will not improve
drainage.
Soil mixes used to grow African violets and other houseplants should
be pasteurized and the pots disinfected before planting. Place a 4-inch
layer of the mix in a flat pan and wet it slightly. Cover the pan with
aluminum foil and seal the edges. Preheat an oven to 180° to 200° F.
Place the soil in the oven and hold it at that temperature for at least
30 minutes before removing it to cool. When reusing pots, wash them
thoroughly and then soak them for 30 minutes in a solution of 1 part
household chlorine bleach in 9 parts water. Rinse the pots until all
traces of chlorine are gone.
Repot violets about once a year, or when the leafless portion of the
stem is about 1 to 1 1/2 inches long. Gently remove the plant from the
pot with a paring knife. Remove all lateral crowns, leaving only the
center crown. Trim off one or two rows of leaves, leaving a wheel of
leaves around the crown. With the paring knife, scrape the neck as you
would a carrot until all the brown plant material is removed and the
neck is firm and green. Break or cut off the bottom half of the root.
Have a clean pot ready to pot up the pruned violet. Gently firm in new
soil around the plant and water well. The pot should be one third the
diameter of the plant; a 4-inch pot is usually adequate.
The usual method of propagation is by leaf cuttings during the
spring. Cut off mature leaves with about an inch of their stalks. Firmly
plant the stalks into sand or vermiculite with most of the leaf blades
exposed. Then, thoroughly water the sand. In greenhouses, the benches of
cuttings are usually covered with light muslin or glass to keep the air
moist. In the window garden, a few cuttings can be covered with a glass
jar or plastic. In two to six months young plants start from the bases
of the stalks. After these have formed two or three small leaves, they
are ready to be potted.
African violets adjust well to the warm temperatures and dry air of
homes. While they require good light, direct sunlight is not necessary.
Windows facing north or east provide favorable light conditions and are
preferable to those exposed to midday and afternoon sunshine during
summer. The sunnier, warmer windows are better in the winter. In
greenhouses, the glass is kept shaded even in the winter.
The best temperatures for African violets are about 60° F at night
and up to 80° to 85° F during the day. The plants become stunted at
cool temperatures and are slow to recover even when put into a warm
place. In hot weather (over 85° F), plants are especially susceptible
to rot.
The soil must be kept moist at all times, but it is desirable to keep
the foliage dry. Drops of water on the leaves cause disfiguring
light-colored spots or rings. Water from either the top or bottom.
Proper watering can be simplified by keeping the pots in watertight
saucers or bowls into which a little water is poured every few days. Or,
use a wick extending through the drainage hole into a saucer of water.
Another effective method is to submerge the pots in peat or sphagnum
moss held in a larger container and apply water to this material as
needed to keep the soil moist within the pots. In either of these
methods, water moves from the saucer or peat by diffusion through the
hole in the bottom of the pot and into the soil ball.
One of the major problems associated with African violet care is
excessive watering, which can lead to root or crown rot. Root and crown
rot caused by the fungus Pythium ultimum may occur on overwatered
plants. All ages of plants may be affected. The crown and roots of these
infected plants turn dark and soft, and the leaves usually wilt.
Infected plants can be lifted easily from the soil. This disease is not
a problem when plants are grown in a pasteurized soil mixture in a
container that allows for proper drainage. Destroy badly diseased
plants, and thoroughly clean and disinfect their containers before
reusing them. Highly prized plants can sometimes be saved if the crown
is not badly decayed. Remove the rotted portion of the crown well above
the line of decay and reroot the plant in sterile medium.
Petiole rot begins as an orange-brown or rust-colored lesion where
the petiole touches the rim of the pot or where it contacts the soil.
This is aggravated by the accumulation of fertilizer salts on the rim of
the porous pot or on the soil surface. An aluminum foil collar on the
rim of the pot and flushing the soil occasionally with heavy watering
will prevent this problem.
The unsightly yellow or white ring and line patterns that
occasionally appear on the leaves are thought to be caused by a sudden
chilling of the leaves by cold water or by the sun shining on wet
leaves. This condition is known as ring spot or chlorosis, and can be
avoided by carefully watering the plants from below with water slightly
warmer than air temperature.
African violets infested with root-knot nematodes are stunted and
weakened. Galls form on the roots, and the crown and leaves become
thickened and distorted. Blisterlike galls also develop on the leaves.
Destroy all infested plants, sterilize their containers, and propagate
new plants only from nematode-free plants.
The leaves of plants grown under greenhouse conditions may become
infected by the fungus Botrytis cinerea. Botrytis blight first
appears as small water-soaked lesions on the underside of the leaf.
These lesions enlarge until much of the leaf turns brown to black.
Flowers may be similarly affected. High humidity, poor air circulation,
and low light intensity contribute to the development of this disease.
Spores of the pathogen are spread by direct contact of leaves. Spacing
the plants so that the leaves of adjacent plants will not touch reduces
spreading to healthy plants. Since infection by Botrytis often follows
mite injury, controlling these pests aids in controlling the disease.
The application of a foliar fungicide may be needed to control severe
outbreaks.
Powdery mildew is a light grey, powdery substance on the stems and
petioles. This shortens the life of blooms and makes the violet
unthrifty. Mildew grows in cool, moist, stagnant air. The best cure is
air circulation--a small fan moving the air in the room will keep it
from developing. Karathane is a good control, as is dusting sulfur when
a very small amount is blown lightly over the plants.
Insects and mites occasionally damage the foliage and flowers of
African violets. Cyclamen mites feed in the plant crown, causing young
leaves and new growth to be stunted, twisted, discolored, and brittle.
When infestations are heavy, leaf hairs become matted and flower buds
fail to open. Cyclamen mites can be controlled by treating infested
plants at weekly intervals for three weeks with dienochlor (Pentac 50WP)
at a rate of 1 teaspoon per gallon of water, or with 2 or 3 applications
of dicofol (Kelthane) as directed on the label. Adding a few drops of
liquid detergent to the spray will increase coverage and provide better
control. Isolate infested plants and be careful while handling them so
you do not accidentally transfer mites from one plant to another.
Mealybugs are small, soft-bodied insects that occur in white, cotton
clusters on the surfaces of leaves, on leaf petioles, and near the bases
of leaf stems. They injure plants by sucking plant juices, which causes
stunting and distortion of the leaves. Mealybugs also excrete a shiny,
sticky substance called honeydew that is highly attractive to ants and
also supports unsightly growths of a dark sooty mold. Heavy mealybug
infestations may cause leaves and plants to wither and die. Mealybugs
can often be eliminated by spraying plants with a jet of lukewarm water
or by removing them with a cotton swab dipped in alcohol. When
infestations are heavy or when many plants are involved, the best
approach is to make 2 to 3 weekly applications of 57% malathion at a
rate of 2 teaspoons per gallon of water. Disulfoton (DiSyston), a
systemic granular insecticide, will also provide satisfactory control if
scratched into the soil and watered in. Hanging a Vapona pest strip in
the vicinity of plants may help prevent reinfestation. Ground or root
mealybugs are tiny, whitish insects that feed on African violet roots,
causing poor plant growth and wilting of leaves between waterings. To
control these pests, avoid overwatering and drench soils with an
insecticide such as malathion or acephate (Orthene).
Stunted plants with curled or distorted leaves may be an indication
of feeding by aphids. Both adults and nymphs are similar in appearance
with soft, pear-shaped bodies, long legs, and antennae. Like mealybugs,
aphids excrete honeydew which gives leaf surfaces a shiny appearance and
supports the formation of sooty mold. Aphids can be washed from infested
African violets with a spray of lukewarm water, or treated with an
insecticide such as 57% malathion at a rate of 2 teaspoons per gallon of
water plus a few drops of liquid detergent. Repeat this treatment after
7 to 10 days. When only a few plants are involved, consider using a
premixed, commercial house plant spray that lists both aphids and
African violets on the label.
Thrips are small, slender insects characterized by long, hair-fringed
wings. They damage African violets by feeding on the leaves and flowers.
Typical leaf injury appears as irregular or streaked silvered areas
dotted with small, black drops of excrement. Flower feeding causes
distorted blooms, discoloration or streaking of petals, and shorter
flower life. Thrips can be controlled with 1 or 2 applications of
premixed, commercial house plant spray containing malathion or Orthene.
Be sure that the product is specifically labeled for both thrips and
African violets.
Some pesticides damage plants, so be certain the product you select
is recommended for use on African violets. In many cases, the label
provides a list of plants known to be sensitive to the pesticide, as
well as those plants for which it is recommended. When possible,
test-treat a few plants and look for signs of plant injury after 2 to 7
days before treating remaining plants.
The authors thank Sybil Behrens, member of the Lincoln African
Violet Society and the National African Violet Society for her
assistance in the preparation of this NebGuide.
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File G182 under: HORTICULTURE A-7, Ornamentals
Revised April 1985; 12,000 printed.
Electronic version issued March 1996 pubs@unl.edu
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Issued in furtherance of Cooperative
Extension work, Acts of May 8 and June 30, 1914, in cooperation with the
U.S. Department of Agriculture. Elbert C. Dickey, Director of Cooperative
Extension, University of Nebraska, Institute of Agriculture and Natural
Resources.
University of Nebraska Cooperative
Extension educational programs abide with the non-discrimination policies
of the University of Nebraska-Lincoln and the United States Department of
Agriculture. |
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