From The Plant Encyclopedia
African Violet, African Violets
|Saintpaulia - Purple African Violet in an indoor situation|
|Category||Perennial, Indoor Plants|
|Species in this genus|
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|Please enter the plant name in this format: 'Latin name - Common Name'|
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- Cultivation: Easy-To-Grow, For-Gardeners, For-Horticulturists
- Light: Dappled, Part-Shade, Shade
- Soil: Rich
- pH: 7
- Moisture: Medium, Well-Drained
- Form: Herbaceous
- Habit: Perennial
- Flower: Large, Medium, Petals, Pink, Purple, White
- Fruit/Seed: Small
- Foliage: Leaves, Succulent, Green
- Uses: Ornamental, Houseplant
Saintpaulia, commonly known as African violet, is a genus of six species of Herbaceous perennial Flowering plants in the family Gesneriaceae, native to Tanzania and adjacent southeastern Kenya in eastern tropical Africa, with a concentration of species in the Nguru mountains of Tanzania. The genus is most closely related to Streptocarpus, with recent phylogenetic studies suggesting it has evolved directly from subgenus Streptocarpella. The common name was given due to a superficial resemblance to true violets (Viola, family Violaceae). Typically the African violet is a common household indoor plant but can also be an outdoor plant. Several of the species and subspecies are endangered, and many more are threatened, due to clearance of their native Cloud forest habitat for Agriculture.
Saintpaulias grow from 6–15 cm tall and can be anywhere from 6–30 cm wide. The leaves are rounded to oval, 2.5–8.5 cm long with a 2–10 cm petiole, finely hairy, and with a fleshy texture. The Flowers are 2–3 cm diameter, with a five-lobed velvety corolla ("petals"), and grow in clusters of 3–10 or more on slender stalks (peduncles). Flower colour in the wild species can be violet, purple, pale blue, or white.
Light: Moderate to bright, indirect, indoor light.
Watering: Keep soil moist to dry, and allow soil around roots to dry out before watering to encourage blooming. Water from the bottom with room temperature water by placing the plastic grower's pot in water, and allowing the plant to absorb the water ( not more than 30 minutes ).
Avoid getting water on the leaves as this can cause spotting damage. For best results, use violet plant food as directed.
In general, African Violets need just enough water to keep the soil moist, but never soggy. Too much water will leave your African Violets susceptible to such deadly pathogens as Pythium, Root Rot and Crown Rot. Overwatering can also cause denitrification, a condition which prevents plants from getting the nitrogen they need.
The water should be room temperature, or as close as possible in temperature to the air around your plants. When the water is too cold, it chills the roots of African Violets, causing leaves to curl down as the water is absorbed into the plant. Also, if watering from the top, cold water can cause leaf spotting. Such spots represent a form of necrosis and, as such, cannot be removed. (Note: Whether the water is the correct temperature or not, it is always important not to get water on the leaves. The only exception to this is when you are spray misting for purposes of quick-feeding or increasing the humidity around your plants. Such misting will not leave behind the large water droplets which, when exposed to the sun, will produce brown spots on the leaves.)
Never use soft water. Soft water increases the saline content. This will alter both the pH and the electrical conductivity of the soil, thereby diminishing your African Violet's ability to absorb water and nutrients. If you have soft water, you may be able to divert water before it reaches the softening unit. If not, you will need to seek an alternative source of water.
Avoid using highly chlorinated water. While some chlorine is actually necessary for photosynthesis to occur, African Violets need very little, i.e., 70-100 ppm. Such minute traces in the water will not be discernible by smell. In fact, if you can smell chlorine, then your water has too much. The consequences of using water with too much chlorine in it include leaf burn and diminished flowering. If you have highly chlorinated water, and no alternative source is available, dispense water into a container and let stand overnight to allow the chlorine gas to escape.
To insure correct watering, you are strongly encouraged to use a recommended self-watering device, such as the Optimara MaxiWell (for 4-inch standard Violets), MiniWell (for 1-inch super miniatures) or the Optimara WaterShip container, a spill-proof, self-watering device for 2-inch miniatures. By providing the correct amount of water, a good self-watering device will greatly reduce the chances of getting any of the deadly fungi which cause plants to rot. In addition, because a good self-watering device waters from the bottom, it eliminates the potential hazards of watering from the top, i.e., leaf spots.
Finally, there are some self-watering devices which, while providing the benefits already mentioned, will also increase the humidity in the area immediately around your Violets. A self-watering device of this type, such as the Watermaid (for pot sizes up to 5-1/2 inches), stores water in an open saucer and draws water into the soil via capillary matting. All of the above self-watering devices are available online at the Selective Gardener, a mail order supplier that specializes in plant care products made specifically for African Violets.
The amount of light that an African Violet receives is important for its health and overall performance. They thrive in moderate to bright, indirect, indoor light.
African Violets, like other plants, need light for photosynthesis. While photosynthesis is most often associated with a plant's green leaves and stems, its most vital function is to convert carbon, hydrogen and oxygen (in the form of carbon dioxide and water) into usable energy called plant carbohydrates. Even when all the essential nutrients are available to the plant, a complete absence of sunlight will literally result in starvation.
More common, of course, is a plant which simply does not get enough sunlight. In such circumstances, an African Violets will stop flowering and its leaves begin to turn yellow. It is also likely that the African Violet, which is not getting enough sunlight, will become rangy as it develops elongated leaves and stems.
While insufficient sunlight can be harmful, too much sunlight can also cause problems. Among other symptoms, too much sunlight will produce brown spots on the leaves and flowers. This is a form of necrosis analogous to sunburn. In addition, too much sunlight can cause the leaves to curl down and may turn variegated leaves entirely green.
African Violets perform best when they receive a lot of indirect sunlight. While African Violets will tolerate direct sunlight very early or very late in the day, they should, in all other cases, be shielded from direct sunlight. For best results, place your Violets in a window where they will receive light most of the day, i.e., a window with western or southern exposure. Adjust your blinds or use a sheer curtain to filter out some of the light. If you have access to a light meter, the correct luminosity for African Violets is 10,000 to 12,000 lux, or about 900 to 1100 foot candles. As an alternative, you can get a reasonable approximation of this light value by simply holding your hand over a Violet during the time when it is receiving the brightest light. If you can barely see the shadow of your hand over the Violet, then it is getting the correct amount of light.
Keep in mind that the duration and intensity of sunlight will vary with the seasons. During the winter months, you may need to allow your African Violets to get more sunlight than they would ordinarily receive. Also, it is important to rotate your African Violets so that they receive an equal amount of sunlight on all sides. They should be rotated one-quarter turn, about once a week or each time you water. If African Violets are not rotated in this manner, they will begin to bend towards the light and grow larger on the side closest to the window. This reaction is not peculiar to African Violets. For almost all plants, it is simply a phototropic response which allows a plant to get optimal sunlight.
If you use artificial lighting, i.e., grow lights, your African Violets will be subject to a number of special considerations. First, when selecting a grow light, it is important to make sure it emits light in both the red and blue spectrums. Red light is essential for African Violets to bloom. Blue light is necessary for photosynthesis to occur and, thus, is vital for the development of green leaves and the production of plant carbohydrates.
Second, keep in mind that the intensity of light will increase as the distance from the source decreases. For this reason, it is important to mount your grow light at the proper distance above the plant. If the African Violet is too close to the grow light, it will begin to develop symptoms similar to those resulting from too much sunlight, i.e., leaf scorch. While you should give preference to any instructions accompanying your particular grow light, grow lights should generally be mounted 18 to 20 inches above the tops of standard African Violets. For miniatures, grow lights may need to be lowered to about 10 to 12 inches above the tops of the plants.
Third, it is important to remember that African Violets need at least eight hours of darkness, each day, in order to bloom. While African Violets need a sufficient duration of light to produce florigen (flowering hormone), florigen itself does not trigger blooming until it is dark. For this reason, African Violets should receive light for no more than 16 hours a day. To properly regulate the duration of light, you may want to consider getting a timer for your grow lights.
Finally, you should be aware of a condition peculiar to African Violets which are cultivated under grow lights. This condition is called Leaf Bleaching. While not all African Violets are sensitive to this condition, those that are will develop leaves which are distinctly lighter on those areas directly exposed to the light. Often, these lighter areas will also exhibit a slight pinkish cast. The only way to treat this condition is to stop using grow lights and begin using sunlight.
In terms of temperature, humidity and other factors of air quality, African Violets thrive in an environment which most people would consider pleasant. Therefore, if you feel comfortable, chances are, your African Violets are feeling comfortable as well. However, in case you are one of those people who thrive in otherwise unhealthy circumstances, you will need to know a little about the conditions preferred by African Violets.
In general, you should keep the air temperature, around your African Violets, as close as possible to 70 degrees F. At the very least, do not allow temperatures to drop below 60 degrees or rise above 80 degrees. Also, while extreme variations in temperature should always be avoided, do not be concerned about slight fluctuations between day and night-time temperatures. In fact, some African Violet hybrids require fluctuations of as much as 10 degrees in order to produce optimal flowering. However, if your African Violets are exposed to extreme temperatures, even for a very short period of time, they may suffer. When the temperature is too warm, plant growth will become rangy (i.e., elongated stems and leaves), leaves will appear dry and shriveled, and flowers will begin to drop off. If you know that the temperature is too warm, gradually reduce it to about 70 degrees F. While doing so, keep in mind that a change in temperature will have a corresponding effect on transpiration and evaporation rates. Therefore, depending on how long your African Violet has been exposed to excessive heat, you may need to decrease the frequency with which it receives water. To gauge the impact on water, it will help to know that the rate of evaporation from leaves drops by half with each decrease of 20 degrees F.
While excessive heat will cause your African Violets to suffer, they are not nearly as deadly as cold temperatures. At the very least, African Violets will stop flowering, and plant growth will be slow. In more severe cases, leaves and flowers will rapidly begin to wilt, and the plant will go into shock. Moreover, cooler temperatures leave African Violets vulnerable to such deadly pathogens as Crown Rot, especially when accompanied by excessive moisture. Depending on the extent to which your African Violet has been exposed to cold temperatures, you may or may not be able to save it. Once an African Violet begins to show symptoms of exposure, it is often too late, especially since it may take up to 36 hours for symptoms to appear.
If your African Violet has been exposed to cold temperatures, move it immediately to a place where the temperature is warm. Next, remove any tissue which has become dark and mushy. This will prevent the spread of rot. Discontinue watering and fertilizing, but maintain high humidity. One way to do this is to employ the bag method. Place your African Violet in a clear plastic bag and close the top with a wire twist. If your African Violet is going to survive, you will begin to see signs of recovery within a few days. However, to allow full recovery, you should keep the Violet bagged for about one week. At this time, once you have removed it from the bag, it should be safe to return your African Violet to its normal watering and fertilizing schedule.
As with relatively warm temperatures, humidity is vital to the health of African Violets. In their native habitat, in the Usambara Mountains of East Africa, the relative humidity is generally about 70 to 80 percent. While this level of humidity would be difficult to maintain in most homes, you should try to provide your African Violets with at least 50 to 60 percent humidity. If the level of humidity is much less than this, an African Violet's transpiration rate will be greater than its ability to absorb water. As a consequence, buds will fail to open, plant growth will be slow, and leaves will begin to appear dry and shriveled.
If necessary, there are a number of ways to increase the amount of humidity around your African Violets. First, you can create a favorable microclimate by grouping your African Violets together. This, by itself, can increase the humidity around your plants by as much as 15 percent. However, when doing so, it is important not to place your African Violets so closely together that the leaves are touching. While maintaining high humidity is essential, it is also important to give your Violets enough room to grow and to maintain sufficient air circulation in order to prevent the growth of potentially dangerous fungi.
Another way to increase humidity is to use a self-watering device, such as the Watermaid, which relies on capillary matting to draw water into the soil. Where capillary matting is used, low humidity is rarely a problem. A similar solution is to place containers of water around the plants. As with capillary matting, evaporation increases the water content in the air surrounding your Violets.
Finally, you may simply want to consider using a humidifier. This will probably be more necessary during the winter months than during than the summer. However, both heating and air conditioning can dry out the air to some extent. In the winter, use a warm-mist humidifier so that the increase in humidity does not affect the air temperature. In the summer, use a cool-mist humidifier.
Because humidity is so important to African Violets, good air circulation also becomes a vital concern. Maintaining good air circulation, especially when the air is damp, helps prevent the growth of such fungi as Botrytis and Powdery Mildew. However, be vigilant to any cold drafts which come in contact with your African Violets. Even when the overall air temperature is within acceptable limits, a cold draft may eventually send an African Violet into shock. In many cases, this can be fatal. At the very least, a cold draft will often cause African Violets to grow lopsided. When this is the case, the source of the draft should easily be located, since an African Violet will become smaller on the side closest to where the draft is originating. In most instances, the source of the draft will be the window in which the Violet has been placed.
One factor of air quality that is often overlooked is the presence of gas or chemical fumes. Common instances of these substances may be found in natural gas (i.e., from a gas stove or other gas-operated appliance), paint fumes or such solvents as those contained in cleaning fluids. Depending on the precise source, gas or chemical fumes can result in pale leaves which are smaller than normal and flowers which turn brown and drop off.
Prolonged exposure to gas or chemical fumes may ultimately be fatal. For these reasons, it is important to insulate your African Violets from any source of gas or chemical fumes. If you suspect that your African Violets are being exposed to one of these substances, it is vital that the source be isolated and remedied. This is as true for your African Violets as it is for you. In fact, if your African Violets are getting sick from the fumes, chances are, you will too.
One way to determine if gas or chemical fumes are present has been suggested by the African Violet Society of America. They assert that a young tomato plant, when in the presence of gas or chemical fumes, will begin to sag within a few hours. However, even if you determine that such substances may be present, it will still be necessary to locate the source and correct it. If unable to do so, you should be advised to contact a specialist, such as a natural gas technician.