What are the precautions for domestic African violets?

Cultivation techniques of African violet

African violet Saintpaulia ionantha (English name: African Violet) is a herbaceous plant of Gesneriaceae, with pilose whole plant and clustered leaves. The leaves are round to oval, about 6 cm long, and the surface of the leaves is covered with fine hairs of different lengths. The lower leaves are grayish green to light purple, and the inflorescence protrudes from the leaves. Each inflorescence axis consists of 8- 10 flowers, which are single and light purple.

1. Production: Light intensity plays a very important role in the appearance of African violets, and it is also a key factor affecting the quality of potted flowers in the production process. However, it is difficult to tell the most suitable light level of African violets, because there are many varieties and there are great differences between different varieties. Generally speaking, 1000- 1200 lux is suitable for most African violets. Under this condition, we can also observe the growth of African violets to judge whether the light is suitable: those varieties with dark green and long petioles need high light intensity, especially those with few flowers; However, varieties with light green leaves need lower light intensity. The proportion of each element in the fertilizer should be controlled at n: P2O5: K2O = 3: 1: 2, and the dosage of commercial fertilizer 19-6- 12 should be 4g every three months. Both liquid fertilizer and slow-release fertilizer are suitable, and a certain proportion of trace elements should be added before mixing the substrate in the basin, or applied in the future fertilization plan. African violets grow well in artificial substrates composed of vermiculite, pine needles, perlite or polyethylene light foam powder. In the production process, we must pay attention to ensure that plants are full of water. Once they are short of water, they will resist growth and delay flowering. The PH value of the soil is preferably between 5.5 and 6.5, and the concentration of soluble salts in the matrix should be lower than 500ppm at the beginning of growth. The best irrigation method for planting and producing African violets is to use the capillary mat method to absorb water from the bottom, because water enters the substrate from the bottom of the basin, which can prevent water droplets from falling on the leaves, so the leaves will not get sick. African violet likes high relative humidity in both growth and flowering stages, so it is suggested that the growth temperature should be kept between 17-20℃, otherwise the growth potential will be reduced. We must pay attention to the selection of suitable varieties before production, because some varieties are very sensitive to heat, and even if the highest temperature is controlled below 20℃ in summer production, it is difficult for this variety to meet the requirements of marketing.

Second, physiological problems: 1. Lose green. Symptoms: The leaves are light green or medium green, but the edges are green. Prevention and control methods: if the flowering situation is good, the fertilizer concentration can be increased or the light can be reduced; Or the trace elements in the culture medium or fertilization scheme are not enough. Sometimes it happens that two compact varieties are under the same management, one pot of flowers is of very good quality, while the other pot of flowers is green, which is caused by the differences between varieties. 2. The leaves are spotted. Symptoms: Light yellow or light green circular spots appear under the leaves, which can appear at the edge or middle, sometimes irregular in shape, or round or white. Prevention and treatment: When the temperature of irrigation water is lower than the surface temperature of leaves, the above symptoms will appear, especially in winter. The water temperature in deep wells is often kept at about 17℃, and this kind of problem rarely occurs when irrigated with such water, unless it is stored outside for a long time and the temperature drops. Remember that the temperature of water should be close to that of plants. 3. The petiole is too long. Symptoms: The petiole is too long, which is not in harmony with the plant shape. Control method: The petiole length is generally caused by too low light intensity and too high nutrient content in the substrate. The simplest way is to reduce the concentration of fertilization. In some cases, we can consider not choosing varieties whose petioles are easy to grow. 4. flowering problem. Symptoms: the plant does not bloom, or the flowering amount is very small, so it cannot bloom normally. Control method: The flowering quantity of plants is less in weak light, so African violets need at least 1000 lux of light intensity, but too strong light will cause the plants to turn yellow, the plant deformation will be short, and even the flowering quantity will be reduced. In summer, excessive temperature will lead to the development of African violets to stop or not develop normally. The best solution is to lower the temperature or choose other varieties.

Third, bacterial diseases: bacterial wilt (the pathogen is Erwinia chrysanthemi) Symptoms: This bacterium can infect all parts of African violets. When the root system is infected, the symptoms are rotten water, sometimes the petals will rot, and the infected petioles and leaves are oily brown and black. When the disease is serious, the plant wilts and then the whole plant dies. Control methods: Although most African violet varieties are sensitive to bacterial wilt, they are only moderately sensitive. Because bacterial diseases are difficult to treat, prevention is very important. It is necessary to reduce the amount of watering and remove the infected plants from the outdoor for destruction in time, because this disease will also infect many other foliage plants.

4. Mycosis: 1. Symptoms of botrytis cinerea: The disease generally occurs on the lower leaves, especially the petiole leaves near the edge of the flowerpot or in contact with the substrate. At first, it is a small watery rot, which will soon spread to the whole leaf or petiole, causing leaf necrosis, and powdery, gray-green fungal spores can be seen on the necrotic leaf or flower. Control method: Avoid the following environmental conditions: insufficient light, high air humidity, poor ventilation and warm day and cool night. 2. Symptoms of root rot (pathogen is Phyophthora parasitica): Root rot caused by Phytophthora is very similar to Fusarium wilt caused by bacteria, and sometimes the two causes are confused. The scientific judgment method is to cultivate pathogens first, and then choose therapeutic drugs. Control method: avoid over watering, and use sterilized flowerpots, substrates and plant materials for production. 3. powdery mildew (pathogen is Oidium sp.) Symptoms: Symptoms occur on flowers, petioles or leaves. It is characterized by the appearance of white powdery circular spots with a diameter of about 1 cm, which are isolated in the early stage and can be connected together in the later stage until the plant is destroyed. Prevention and treatment: the disease generally does not cause serious losses. Because the symptoms are obvious, it can be prevented by spraying drugs as soon as possible.