Ferns are popular additions to homes and gardens, bringing a lush, green texture to any space. While they often thrive during warmer months, winter presents specific challenges related to changes in light intensity, temperature, and indoor air dryness. Successfully caring for a fern through the colder season requires adapting your routine to accommodate the plant’s reduced growth rate and environmental shifts. This adaptation ensures the plant remains healthy until spring.
Differentiating Tropical and Temperate Ferns
The appropriate winter care plan depends entirely on the fern’s natural habitat, categorizing them as either tropical or temperate. Tropical varieties, such as the Boston fern or Maidenhair fern, are typically grown as indoor houseplants and need active care to maintain growth. These species are not frost-tolerant and will fail if exposed to freezing temperatures.
Temperate ferns, including the Christmas fern and Ostrich fern, are hardy perennials suited for outdoor gardens that enter a natural dormancy. These outdoor varieties are adapted to survive cold temperatures by temporarily halting growth. Recognizing which type of fern you have is the first step toward providing the correct seasonal protection.
Optimizing Indoor Winter Conditions
Indoor ferns struggle most with the dry air produced by central heating systems. Heating significantly lowers the relative humidity inside homes, often dropping it below the 50% threshold required to prevent fronds from browning. To counteract this, place the fern near a dedicated room humidifier to maintain consistent moisture levels.
A simple method is to set the potted fern on a shallow tray filled with pebbles and water, ensuring the pot bottom does not sit directly in the water. This setup creates a localized microclimate of higher humidity as the water evaporates. Temperature stability is also important, as sudden drops or spikes can shock the plant.
Keep indoor ferns away from cold drafts originating from windows and exterior doors, and avoid direct blasts of hot air from heat vents or radiators. Most tropical ferns prefer a stable temperature range between 60°F and 75°F. Since natural light is greatly reduced in winter, you may need to move the fern to a brighter location.
A spot near an east or south-facing window that provides bright, indirect light is ideal to compensate for lower light intensity. If natural light is extremely limited, consider supplementing with a grow light to prevent the fern from becoming weak. Keep the fern a few inches away from cold window glass, which can transmit chilling temperatures to the foliage.
Adjusting Water and Nutrient Intake
The primary cause of indoor fern decline in winter is often overwatering, as the plant’s metabolism slows down considerably. With reduced light and cooler temperatures, the fern’s demand for water decreases, and the soil takes longer to dry out. Allowing the soil to remain constantly soggy can quickly lead to root rot, a fungal disease that suffocates the roots.
To avoid this, drastically reduce the frequency of watering and only apply water when the top inch of the soil feels dry. Insert a finger about an inch deep into the potting mix to gauge the moisture level before watering. When you water, soak the soil thoroughly until water drains from the bottom, then discard any water collected in the saucer immediately.
Fertilizer application should be stopped completely or severely reduced during the winter rest period. Ferns have minimal nutritional needs when they are not actively producing new fronds. Applying fertilizer during this time can stress the roots and lead to a buildup of mineral salts in the soil. Resume a light feeding schedule only when you observe the first signs of vigorous new growth in the spring.
Protecting Outdoor and Dormant Varieties
Temperate ferns that remain in the garden are adapted to dormancy, requiring physical insulation rather than active growth support. Applying a thick layer of organic mulch, such as shredded leaves or wood chips, over the root zone helps regulate soil temperature. This insulation prevents repeated freezing and thawing cycles that cause frost heaving, which damages the roots.
For these outdoor ferns, it is beneficial to leave any dead or brown foliage intact throughout the winter. The spent fronds naturally collapse over the plant’s crown, providing an additional layer of protection. This foliage can be trimmed back in late winter or early spring just before the new fiddleheads begin to emerge.
Container-grown outdoor ferns are more vulnerable to winter cold because their roots lack the insulation of the surrounding ground. Move these potted plants into a sheltered, unheated space like a garage or cold frame once sustained freezing temperatures are expected. In this sheltered dormancy, they need minimal watering—just enough to keep the potting mix from becoming bone-dry.