What to Do With Outdoor Fern Plants in Winter

Outdoor ferns provide graceful, reliable foliage for shaded places all through the warm months of this year. Species vary in cold tolerance, so that their therapy during the winter also varies. Species from mild-winter or subtropical habitats cannot tolerate freezing temperatures and must be protected to endure. Some temperate-climate ferns may be hardy to U.S. Department of Agriculture plant hardiness zone 3, in which average yearly extreme minimum temperatures are minus 30 to minus 40 degrees Fahrenheit, however they become deciduous in colder zones. Move ferns in containers into sheltered areas or inside, based on their cold tolerance, to endure winter.

Garden Evergreen Ferns

Evergreen ferns keep their leaves all winter long. Keep the plants watered if winter rainfall is scanty. Old leaves become unsightly since the new leaves are emerging. Prune away old leaves annually in late winter or early spring. A few examples of garden evergreen ferns are coastal wood fern (Dryopteris arguta), growing in U.S. Department of Agriculture plant hardiness zones 7 through 10; Western sword fern (Polystichum munitum), growing in USDA zones 3 through 8; and leatherleaf fern (Rumohra adiantiformis), hardy in zones 8 through 11. Holly, or even Christmas, fern (Polystichum acrostichoides.) Is native to North America and grows in USDA zones 5 through 9.

Garden Deciduous Ferns

Some ferns make it possible for fronds to perish for the winter. Cut back dead fronds in early winter, and mulch the plants after pruning to further protect underground roots and crowns. New growth emerges in the spring. Southern maidenhair fern (Adiantum capillus-veneris) produces lacy mounding foliage atop wiry stems in USDA zones 6 through 9. Northern maidenhair fern (A. pedatum) rises in zones 3 through 8. Maidenhair ferns need summertime humidity.

Frost-Tender Container Ferns

Since Victorian times, ferns are popular container plants for growing outdoors in summer and inside in winter. Frost-tender ferns, such as Boston fern (Nephrolepis exaltata), are hardy in USDA zones 8 through 11 and need protection below zone 8. Boston ferns are often utilized as a warm-season hanging basket plant for temperate-climate porches and patios. For them to survive, move Boston ferns inside before the first frost. Plants need a cool, brightly lit place such as near a north- or east-facing window. Keep humidity with humidifiers, misting, or pebble trays.

Cold-Hardy Container Ferns

Even if a fern can withstand freezing temperatures in the garden, even when in a grass it is vulnerable to cold damage because less dirt is insulating roots and rhizomes. Protect container-grown ferns from extremes of cold by moving them into sheltered locations, wrapping the pot using insulating materials or surrounding the grass with layers of dirt or mulch. Place mulch over the surface of the soil as well.

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