Ferns are popular for their graceful, feathery fronds, adding a touch of lush, ancient greenery to gardens and homes. Preparing them for the cold season is essential for their long-term health, but the approach varies dramatically depending on the species. The most common error in winter fern care is treating all varieties the same way, when their survival strategy is split between remaining outdoors in dormancy and requiring protection indoors.
Understanding Your Fern’s Needs
A fern’s winter care is determined by its hardiness, separating species into two main categories: hardy and tropical. Hardy ferns, such as the Ostrich Fern or Christmas Fern, can withstand cold temperatures and overwinter in the ground in temperate climates. These varieties enter dormancy when the weather cools, often losing their foliage entirely or remaining semi-evergreen.
Tropical or tender ferns, which include common varieties like the Boston Fern or Macho Fern, are native to warmer, humid regions and cannot survive frost. If your fern was purchased as an indoor houseplant or used outdoors in a container during the summer, it is a tropical variety requiring indoor protection. To confirm your fern’s type, check the original plant tag or your USDA hardiness zone to determine if the species is rated to survive your region’s typical winter low temperatures.
Winterizing Hardy Outdoor Varieties
Hardy ferns remaining in the ground need preparation to insulate their crowns and root systems from freezing temperatures. For deciduous types that die back, cut the fronds down after a hard freeze to tidy the garden and make way for new growth. For evergreen varieties, only remove brown, damaged, or yellowing fronds, as the healthy foliage provides insulation throughout the winter.
The primary defensive measure is applying a generous layer of protective mulch. Spread two to three inches of organic material, such as composted leaves, pine needles, or straw, around the base of the plant. This layer regulates soil temperature, preventing damaging freeze-thaw cycles that can heave the plant’s crown out of the ground.
Once the ground is frozen solid for the winter, the plant’s metabolic processes slow, and watering should cease entirely. Prior to the deep freeze, ensure the soil is consistently moist, but not saturated, as waterlogged soil around a dormant plant can lead to root rot. The protective mulch layer will also help retain moisture, keeping the roots cool and damp throughout the colder months.
Caring for Tropical Ferns Indoors
Tropical ferns must be moved indoors before the first frost, ideally when nighttime temperatures consistently drop below 55°F. Before relocation, thoroughly inspect all parts of the plant, including the undersides of the fronds and the soil surface, for hitchhiking pests such as mealybugs or scale. A preventative spray with insecticidal soap or a strong water jet helps ensure you do not introduce unwanted insects into your home environment.
The main challenge of indoor winter care is maintaining the high humidity these plants naturally require. Central heating systems drastically lower indoor air moisture, which can cause delicate fern fronds to develop brown, crispy tips. To counteract this, place the fern on a pebble tray filled with water, ensuring the pot’s base does not sit directly in the water to avoid root rot.
Grouping ferns and other moisture-loving plants together can create a beneficial microclimate by increasing local humidity through collective transpiration. Misting offers only a temporary increase in humidity and is less effective than using a room humidifier or placing the fern in a naturally moist area like a bathroom. Place the fern in a spot that receives bright, indirect light, such as a few feet away from an east or west-facing window, since lower winter light levels can cause the plant to struggle.
Indoor ferns need a reduced watering schedule during winter, as their growth naturally slows down. The goal is to keep the soil consistently moist, but never soggy, allowing the top inch or two of soil to dry slightly before watering again. If the indoor temperature is consistently below 60°F, only water when the soil feels dry to the touch to prevent the roots from sitting in cold, wet soil.
Transitioning Ferns Back to Spring
As the danger of frost passes and temperatures warm, the winterizing process reverses, preparing the ferns for the new growing season. For hardy outdoor ferns, gradually remove the protective mulch layer to allow the soil to warm and prevent the crown from remaining too wet, which can encourage rot. Resume a regular watering schedule once new growth appears and the soil is no longer frozen.
Tropical ferns that spent the winter indoors require a slow reintroduction to the harsher outdoor elements, a process known as “hardening off.” Begin by placing the potted fern outside in a sheltered, shady location for just a few hours daily. Over one to two weeks, gradually increase the duration of its outdoor exposure and the amount of indirect sunlight it receives. This acclimation prevents sun-scald and shock, ensuring the plant is robust enough to thrive once moved back to its summer spot.