Impatiens (Impatiens walleriana) is an annual flowering plant that is easy to grow and provides abundant flowers from late spring to fall. They have glossy, medium-sized leaves and bear 1 to 2 inch red, white, pink, violet or orange flowers in single or double varieties. Impatiens grow to 12 to 18 inches tall. Although generally disease and pest resistant, impatiens can develop problems causing white spots on leaves.
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Grow impatiens from seed or seedlings purchased from your local garden center. Start seeds indoors eight to 10 weeks before the anticipated transplant date when all frost danger has passed. Outdoors, impatiens prefers partial shade with moist, well-draining soil. Two to four hours of direct sunlight is all that impatiens need. Plants grown in heavy shade bloom less but grow taller. Water them at least once each week during dry weather and apply a slow-release fertilizer at planting, according to Iowa State University horticulturalist Richard Jauron.
Impatiens are generally known as hardy plants with few pest and disease problems. However, temperature and irrigation variations may weaken the plant, allowing insects and pathogens to take hold. Monitor the impatiens closely for infestation signs on stems and the leaves’ undersides. Remove discolored, wilted or stunted leaves and blossoms, as these are the signs of plant problems. Treating impatiens problems early helps protect the plant’s health and blooming ability.
Powdery mildew is a white, mealy fungus growing on the tops of leaves. A number of different plant pathogens cause it. Powdery mildew develops when there is a fluctuation of warm and cool temperatures with a relative humidity of 85 percent. The mildew appears as white spots, which is very distinct on red flowers. When the fungus grows heavily, it appears as a grayish growth on leaves. Triflumizole fungicide helps protect plants from this disease, according to Penn State University. Chlorthalonil is recommended if the plants are not flowering.
Thrips are small insects about 1/16 inch long that collect on the leaves’ undersides. They are slender with wings and may be yellow-brown to dark-brown in color. These insects suck juices from the leaves, causing discolored, pale spots on flowers. Thrips in small numbers do not harm the plant’s health, but large numbers can cause severe distortion. Spinosad controls the population.
Impatiens Necrotic Leaf Spot
Impatiens necrotic leaf spot, formerly called tomato virus leaf spot, is a disease commonly afflicting impatiens and other garden flower plants. Thrips transmit this disease. It spreads rapidly throughout the garden bed. Symptoms include darkened, concentric areas, browning leaf edges and general decline of the plant.