Impatiens, including the classic Impatiens walleriana and the larger-leafed New Guinea Impatiens (Impatiens hawkeri), are popular bedding plants known for their bright, prolific blooms. These shade-loving flowers are technically tender herbaceous perennials in their native tropical habitats, capable of living for multiple years. However, in most temperate regions, they are cultivated as annuals, completing their life cycle within a single growing season before dying off. Death can be a predictable seasonal occurrence or a sudden, premature event triggered by environmental failure or disease.
The Expected End: Death by Seasonality
The most common cause of death for garden Impatiens is the arrival of cold weather. As tropical plants, they are extremely sensitive to chilling temperatures and frost. Impatiens begin to suffer visible damage and decline when temperatures consistently drop below 40°F (4°C).
The plant’s soft, succulent tissues contain a high percentage of water, making them susceptible to freezing. A single hard frost (32°F or 0°C) causes ice crystals to form within the cells, rupturing the cell walls. This leads to the immediate collapse and blackening of the entire plant. For gardeners in non-tropical zones, this seasonal demise marks the natural end of the plant’s annual display.
Fatal Environmental Stressors
Beyond predictable cold, Impatiens are susceptible to rapid death caused by cultural errors, primarily improper water management. They require consistently moist soil but cannot tolerate being waterlogged, which quickly leads to root rot. Root rot starves the plant of oxygen and water, causing the stems to soften and the plant to collapse.
Conversely, Impatiens have a low tolerance for drought and will wilt rapidly if the soil dries out completely. While wilting may be reversible with immediate watering, prolonged water stress causes the plant to drop leaves and flowers, which can lead to death if the drought is severe. Light exposure also becomes a stressor, as the plants prefer part to full shade. Too much direct afternoon sunlight can scorch the leaves, causing brown patches and overall plant decline. Prolonged air temperatures above 86°F (30°C) can induce heat stress, causing the plant to wilt and suffer leaf loss even with adequate soil moisture.
Sudden Collapse: Disease and Pests
The most destructive cause of sudden death for Impatiens walleriana is Impatiens Downy Mildew (IDM), caused by the water mold Plasmopara obducens. Initial symptoms often appear as subtle yellowing or stippling on the leaves, which can be mistaken for a nutrient deficiency. As the disease progresses, the upper leaves may curl downward. A characteristic white, fuzzy growth—the organism’s sporangia—becomes visible on the underside of the leaves, especially in cool, humid conditions.
The infection rapidly leads to defoliation, shedding nearly all leaves and flowers, leaving behind only bare, green stems. Complete plant loss can occur in four to six weeks once symptoms are noticed, as the stems eventually collapse. New Guinea Impatiens exhibit high tolerance to IDM, making them a suitable alternative for gardeners. Besides IDM, dry conditions can invite pests like spider mites, which cause yellow stippling and curled leaves, while excessive moisture promotes fungal issues like Botrytis.
Extending the Growing Season
Although typically grown as annuals, Impatiens are tender perennials and can be preserved indoors through the winter. To successfully overwinter a plant, bring it inside before the first forecast of chilling temperatures, generally when nighttime lows dip below 50°F (10°C). Before moving the plant indoors, it should be heavily pruned, cutting the stems back by one-third to two-thirds, and inspected for pests or disease.
Once inside, the plant requires bright, indirect light, such as a north or east-facing window. Watering frequency must be significantly reduced during the dormant indoor period, allowing the top inch of soil to dry out between waterings to prevent root rot. Maintaining a consistent room temperature, ideally between 65°F and 75°F (18°C and 24°C), will keep the plant alive until it can be safely moved back outside after the danger of spring frost has passed.