Hanging ferns, such as the popular Boston and Kimberly Queen varieties, are tropical plants that cannot survive cold temperatures. These non-hardy varieties suffer damage or death if exposed to frost or sustained temperatures below 40–50°F. Successfully overwintering ferns requires providing a controlled indoor environment that mimics their native humid habitat until they can return outdoors in the spring.
Preparing the Fern for Indoor Life
The transition indoors must happen before temperatures drop below 50–55°F, well ahead of the first hard frost. Freezing temperatures cause irreparable damage to the fronds and root system. Before relocating the plant, a thorough inspection and cleaning is necessary to prevent introducing outdoor pests into the home.
First, prune the fern by removing any dead, yellowed, or overly long fronds at the base to shape the plant and reduce its size. Reducing the foliage helps the plant manage environmental shock and simplifies pest inspection. Next, wash the fern using a strong spray of water to clean the foliage, including the undersides of the fronds, and the outside of the pot.
This washing dislodges common hitchhiking pests like spider mites, mealybugs, and scale insects before they spread to other houseplants. If a heavy infestation is found, apply a targeted treatment with insecticidal soap and allow it to dry before moving the fern inside. Some gardeners soak the entire pot in water for a few hours to force out slugs or worms hiding in the soil.
Optimal Indoor Environment
Once the fern is inside, establishing a stable, suitable habitat is required for its long-term health. Ferns thrive in bright, indirect light, often found near an east or north-facing window. Direct sun, particularly from a south or west-facing window, can scorch the delicate fronds and must be avoided.
Maintaining the correct temperature is important, with an ideal range of 60–75°F during the day and slightly cooler temperatures at night. The plant should be placed away from cold drafts, such as leaky windows, or direct heat sources like heating vents, which rapidly dry out the foliage. The biggest indoor challenge for ferns is the low humidity caused by central heating systems during winter.
These plants naturally require high atmospheric moisture, so supplemental humidity is almost always needed. Strategies include placing the fern on a pebble tray filled with water, ensuring the pot does not sit directly in the water, or grouping several plants together to create a localized humid microclimate. Using a cool-mist humidifier nearby is the most effective method, aiming for a humidity level of 50–60% around the plant.
Adjusting the Winter Care Schedule
The winter care routine must differ significantly from the summer schedule because the plant’s growth slows down considerably. During the cooler, darker months, the fern enters a state of semi-dormancy, meaning its metabolic rate and water uptake decrease dramatically. Overwatering is the biggest threat to an overwintering fern and quickly leads to lethal root rot.
Reduce the frequency of watering, allowing the top inch or two of the soil to dry out before water is applied again. This ensures the roots receive moisture without remaining perpetually saturated. Use room-temperature water when watering to prevent shocking the plant’s root system.
Furthermore, all fertilization must cease throughout the winter period. Since the plant is not actively growing, it does not require nutrients, and applying fertilizer can damage the roots. While misting can provide a temporary, minor boost in humidity, it is not a sufficient substitute for sustained humidity methods. Occasional browning or dropping of a few fronds is normal during this slowdown, but consistent health should return with the increased light and warmth of spring.