The Boston Fern (Nephrolepis exaltata) is a popular houseplant often enjoyed outdoors during warmer months for its lush, arching fronds. Since this fern is tropical, it cannot survive freezing temperatures or even mild winter cold outside in most regions. For those living outside of USDA hardiness zones 8 through 11, winterizing the plant and bringing it indoors is mandatory for its survival. This transition requires careful preparation and maintenance to keep the fern healthy until it can return to the outdoor environment.
Preparing the Fern for Indoor Transition
The ideal time to move your Boston Fern indoors is before nighttime temperatures consistently drop below 45 to 50 degrees Fahrenheit (7 to 10 degrees Celsius). Waiting until after the first frost can shock the plant and make it susceptible to pests and diseases. Preparation involves physically readying the fern for its smaller indoor space and lower light conditions.
Before the move, prune the fern to reduce its size and remove any compromised foliage. Cut back long, straggly fronds and remove all yellowed, brown, or dead leaves at the base of the plant. This pruning reduces the plant’s overall footprint and helps to minimize the shock of moving indoors. Finally, clean the exterior of the pot and gently clear the soil surface of any accumulated debris, which can harbor insect eggs or fungal spores.
Essential Steps for Pest Management
A thorough pest inspection and treatment is necessary before bringing any outdoor plant inside to prevent infesting other houseplants. Boston Ferns are susceptible to common pests, including mealybugs, scale insects, and spider mites. Inspect the entire plant closely, paying attention to the undersides of the fronds and where the leaf meets the stem, as these are common hiding spots.
Treatment involves applying a solution of insecticidal soap or neem oil, ensuring complete coverage of the plant’s surface. For heavy infestations, wash the fern with a strong blast of water to physically dislodge the insects before applying treatment. After treatment, keep the fern in isolation for one to two weeks in a separate room to ensure no pests remain before placing it near other indoor plants.
Creating the Optimal Indoor Environment
Once inside, the Boston Fern requires specific conditions to survive the winter without going dormant. The ideal temperature range for active growth is consistently between 55 and 65 degrees Fahrenheit (13 to 18 degrees Celsius). Keep the fern away from cold drafts from windows or doors and direct heat sources like vents or radiators, as both cause rapid fluctuations in temperature and humidity.
Boston Ferns prefer bright, indirect light, such as that provided by an east-facing window, which receives gentle morning sun. Avoid placing the fern in a south or west-facing window where intense afternoon light can scorch the fronds. Maintaining high humidity is important during winter, as indoor heating systems dry out the air considerably.
To increase humidity, place the pot on a saucer filled with pebbles and water, ensuring the pot does not sit directly in the water. Misting the fronds provides temporary relief, but a more consistent solution is using a room humidifier or grouping the fern with other plants to create a localized microclimate. Watering frequency must be significantly reduced in winter; only provide water when the top inch of soil feels dry to the touch to prevent root rot.
Reintroducing the Fern Outdoors in Spring
When the danger of the last frost has passed and nighttime temperatures are reliably above 50 degrees Fahrenheit (10 degrees Celsius), the fern can be moved back outside. Before settling it into its permanent summer spot, “hardening off” is necessary to prevent sun scald and shock. This involves gradually reintroducing the plant to the outdoor elements over 7 to 10 days.
Start by placing the fern in a shady, protected outdoor location for a few hours each day, such as under a porch or a dense tree canopy. Gradually increase the duration of its time outdoors and slowly expose it to slightly brighter light each day. Once this transition is complete, return to a regular summer watering and fertilization routine to promote new, vigorous growth.