Moving non-hardy ferns, such as Boston or Kimberly Queen varieties, indoors for the winter is often necessary. These tropical and subtropical plants cannot tolerate frost; freezing temperatures cause cellular damage and plant death. Successful overwintering requires carefully managing the transition and maintaining specific conditions inside the home for several months. This guide ensures your fern remains healthy until it can safely return outside in the spring.
Preparing the Fern for the Move Indoors
The transition should begin well before the first anticipated frost date, ideally when nighttime temperatures consistently drop below 50°F. Prune back any old, yellowed, or damaged fronds before the move to minimize the plant’s energy expenditure indoors. This selective removal also improves air circulation around the crown, helping deter fungal issues in stagnant indoor air.
Thoroughly cleaning the plant and its container prevents indoor pest infestations. Wipe down the exterior of the pot to remove dirt, debris, or hitchhiking organisms like snail eggs. The plant itself should be closely inspected, particularly the undersides of the fronds and the soil surface, for common outdoor pests.
Pests such as aphids, whiteflies, or spider mites can quickly spread to other houseplants indoors. If pests are detected, treat the fern with insecticidal soap or horticultural oil before bringing it inside. Isolate the fern in a separate room for one to two weeks after treatment for monitoring. This confirms the plant is pest-free before it joins any established indoor collection.
Creating the Ideal Indoor Environment
Once inside, the fern needs specific conditions to mimic its natural, humid, understory environment. Temperature regulation is important, and ferns thrive in a range between 55°F and 75°F. Avoid placing the fern near cold drafts from windows or doors, or near drying heat sources like radiators or forced-air vents.
Humidity is crucial for a healthy indoor fern, given that typical home heating systems drastically reduce air moisture. To counter the dry air, place the fern on a shallow tray filled with pebbles and water, ensuring the bottom of the pot does not sit directly in the water. Grouping the fern with other houseplants naturally increases the local humidity through collective transpiration.
If ambient humidity remains low, a small room humidifier positioned nearby provides consistent moisture for the fronds. Ferns prefer bright, indirect light, often doing well near an east-facing window or a few feet from a south or west-facing window. Since insufficient light during winter can cause weak growth, supplementing with a simple grow light may be necessary.
Troubleshooting Wintering Problems
Even with optimal preparation, certain problems can arise as the fern adjusts to the indoor climate, and prompt diagnosis prevents long-term damage. The dry air in heated indoor spaces is ideal for common pests like spider mites and scale insects. Spider mites cause a dusty or stippled appearance on fronds and may leave fine webbing. Scale appears as small, hard, brown bumps, usually along the stems.
Treating these pests often involves physical removal, such as dabbing scale with an alcohol-dipped cotton swab or washing the plant with insecticidal soap. Physical symptoms also indicate environmental stress related to water or humidity. Brown and crispy tips on the fronds commonly signal that the air is too dry or that watering has been inconsistent.
Maintaining consistent soil moisture is necessary; the soil should feel slightly damp but never waterlogged or completely dried out. Excessive and sudden leaf drop often signals temperature shock or a sudden change in light exposure. Moving the plant to a more stable location, away from temperature extremes, usually resolves this issue.
Reintroducing the Fern Outdoors in Spring
The final stage involves moving the fern back outside once the danger of the last spring frost has passed. Bringing the fern out too soon risks damage, as tender new growth is highly susceptible to freezing temperatures. The transition back to intense outdoor sunlight must be gradual to prevent severe sun scorch on the foliage.
This process, known as “hardening off,” and it acclimatizes the plant to the stronger ultraviolet light and fluctuating outdoor temperatures. Start by placing the fern in a deeply shaded, sheltered location for one to two hours per day. Over one to two weeks, slowly increase the duration of its time outdoors and slightly increase its light exposure.
Once fully hardened off, the fern can be moved to its permanent outdoor location for the season, which should offer partial to full shade. A location beneath a dense tree canopy or on a covered porch mimics the forest floor environment where ferns naturally thrive. This careful reintroduction minimizes shock and ensures the fern quickly resumes vigorous growth throughout the warmer months.