New Guinea Impatiens (Impatiens hawkeri) are vibrant, showy plants native to tropical regions. In temperate climates, they are cultivated as annuals because they are extremely sensitive to cold temperatures and cannot survive frost. To save these plants for the following growing season, careful overwintering indoors is necessary. This transition and subsequent indoor care require attention to detail to ensure the plant remains healthy until spring.
Pre-Winter Preparation and Timing
The process of preparing New Guinea Impatiens for their indoor stay must begin before the first significant temperature drop to avoid cold shock. The ideal time to move the plants inside is when nighttime temperatures consistently fall to 50–55°F. Waiting too long risks exposing the plant to damaging cold, which can weaken the plant.
Before moving a plant inside, a thorough cleaning is required to prevent the introduction of outdoor pests into the houseplant collection. Inspect the foliage and stems for any signs of insects, such as spider mites, aphids, or whiteflies. It is recommended to prune the plant back significantly, reducing its size by about one-third to two-thirds of its stem length. This reduction helps the plant manage the lower light conditions indoors.
Cleaning the foliage with a gentle spray of water or a weak solution of insecticidal soap can dislodge any lingering pests or eggs. This preparation phase minimizes the risk of a pest infestation, which is a common challenge when overwintering plants. Once cleaned and pruned, the New Guinea Impatiens should be slightly watered and immediately moved to its prepared indoor location.
Establishing the Indoor Growing Environment
The most important factor for indoor survival is simulating the bright, warm conditions of the plant’s tropical origin. New Guinea Impatiens require bright, but indirect light, which is often best provided by a south-facing window with sheer curtains or an east-facing window. If natural light is insufficient, supplemental artificial lighting, such as a full-spectrum grow light, should be provided for 12 to 14 hours per day.
The indoor temperature must remain consistently warm, ideally between 60°F and 75°F (15°C to 24°C). The plant should be placed away from cold drafts from exterior doors or windows, as well as away from direct heat sources like radiators or heating vents, which can cause temperature fluctuations and stress. Maintaining the high humidity that these plants thrive in is a major challenge in dry indoor environments.
To address the low humidity of heated homes, several methods can be employed to increase moisture in the air around the plant. Placing the pot on a shallow tray filled with pebbles and water, ensuring the pot bottom does not sit directly in the water, allows for localized humidity as the water evaporates. Daily misting of the foliage or placing a small humidifier nearby can also help maintain the necessary humid microclimate.
Winter Maintenance and Pest Monitoring
Once the plant is settled in its winter location, the care routine must shift to reflect its reduced metabolic activity. The frequency of watering must be significantly reduced compared to the active growing season, as the plant uses less moisture in cooler temperatures and lower light. The soil should be allowed to dry out slightly, with watering occurring only when the top inch or top third of the soil feels dry to the touch. Overwatering is a common mistake and can quickly lead to root rot.
Fertilization should be completely stopped during the winter months, as the plant is not actively growing or flowering. Providing nutrients during this dormant phase can lead to weak, leggy growth that is easily damaged. The focus of winter maintenance should be survival and health, not vigorous growth.
Continuous inspection for houseplant pests is an important weekly task, as the dry indoor air often provides ideal conditions for them to proliferate. Spider mites and aphids are the most common culprits, often detected as tiny webbing or clustered insects on the undersides of leaves. If a pest outbreak is observed, prompt treatment with insecticidal soap or a gentle neem oil solution should be applied to prevent the infestation from spreading to other plants.
Transitioning Back Outdoors
The final step in the overwintering cycle occurs in the spring when outdoor conditions once again stabilize. The plant should not be moved outside until all danger of frost has passed and nighttime temperatures are reliably above 55°F. Moving the plant out too early risks both cold damage and temperature shock.
The process known as hardening off gradually acclimates the plant to the intense light and fluctuating temperatures outdoors. Begin by placing the New Guinea Impatiens in a shady, protected outdoor spot for only a few hours each day. Over a period of seven to ten days, slowly increase the duration of its outdoor exposure and gradually introduce it to brighter light. This prevents leaf scorch and shock, ensuring the plant is prepared to resume its active outdoor growth for the season.