Hardy Ferns

Printer Friendly Version

Hardy ferns are tolerant of cold winter temperatures and can be grown outdoors year-round. Many ferns are both cold and heat tolerant — these make the best garden plants for the South. There are ferns that will grow in every area of South Carolina. Use the chart below to select the ones that will perform well in your area.

While most ferns average between one and three feet tall and wide, some, such as resurrection fern, grow only a few inches tall. Others, like royal and ostrich ferns, can tower to six feet. Most ferns are slow growing and can take several years to reach their mature size.

All ferns prefer well-drained soil high in organic matter. For heavy clay soil, mix a 2-inch layer of composted pine bark or other organic material into the top 10 inches before planting to improve drainage. Poultry grit (crushed granite) also works well to improve drainage and should be used in addition to organic material, not as a substitute. Sandy soils also benefit from a 2-inch layer of organic material tilled in because it helps them retain moisture. It is wise to prepare a large area for ferns before planting, not just individual holes. This will help prevent water from filling the holes and rotting the roots. Ferns may also be grown in raised beds, which provide good drainage.

Most ferns require a moist, shady spot to grow — either in a wooded area or near the north side of a building. Many need plenty of moisture during the growing season and should be given an inch or more of water per week if not supplied by rains.

While most of the ferns discussed here prefer acidic soils with a pH of 4 to 7, both southern and northern maidenhairs as well as ebony spleenwort prefer a more alkaline soil with a pH of 7 to 8. Have a soil test done to check the pH, and mix ground limestone or crushed oyster shells at recommended rates into the planting area if your soil is acidic. For more information, see HGIC 1652, Soil Testing and HGIC 1650, Changing the pH of Your Soil.

Fertilizing should be done in spring, just after new growth has begun. Ferns are very sensitive to over fertilizing, so it is best to use a slow release fertilizer, such as Osmocote 14-14-14. Complete organic fertilizers also work very well. Always follow package instructions for fertilizer rates.

A 2- to 3-inch layer of leaves or pine straw, applied in the spring and in the fall, is an excellent mulch for ferns. Ferns grown in wooded areas benefit from the falling leaves and pine needles in the fall. See the chart below for cultural requirements of specific ferns.

Ferns may be propagated by division or from spores (see THE FERN LIFE CYCLE, below). For the home gardener, division is the most practical method.

How do you know when your ferns need dividing? If you’ve noticed that the center of the clump is hollow or dead and/or the leaves are smaller than usual, it’s probably time to divide. You may also divide if you simply want more plants.

Generally, division is done every three to five years, and can be done right after the first frost in the fall (when the leaves have dropped). Do not fertilize fall transplants. Ferns may also be divided in very early spring, just as the new growth is emerging, if care is taken not to damage the delicate new leaves.

There are three different methods for dividing ferns. Rhizome division involves ferns that grow from thick underground stems called rhizomes. Clump division is a method used for ferns with fibrous roots. Edge division involves cutting divisions from the outside edges of a clump. See the chart below for the division method of each fern. For information on how to divide, see HGIC 1150, Dividing Perennials.

Ferns reproduce in a unique way. Instead of growing from seeds, ferns grow from spores. Ever wonder what the little brown dots are on the back of a fern leaf? They’re spore cases, full of many spores. When a spore germinates, it becomes a small leaf-like structure called a prothallium. The prothallium produces both male and female sexual organs. When the female organs become fertilized by the male organs, small fern plants begin to grow. In some ferns it can take as long as six months for the first fronds (leaves) to appear after sexual fertilization.

Ferns give a delicate and airy quality to a shady garden. Many will grow in full shade, in areas where other plants will not grow. Cinnamon, royal and southern shield ferns will grow in full sun if constant moisture is available. For an elegant groundcover in a shady spot, try hay scented, ostrich, sensitive, broad beech or southern shield ferns. Fine textured ferns contrast nicely with the large leaves of hostas, the shiny leaves of hellebores and the colorful leaves of heucheras.

Ferns have few pest problems if care is taken to meet their growing requirements. Maidenhair and ebony spleenwort ferns can sometimes get scale insects, which can be treated with horticultural oil or insecticidal soaps. Slugs will occasionally eat the young fronds of variegated shield, deer, hayscented or southern shield ferns. Diatomaceous earth works well on slugs. For more information on slugs, see HGIC 2357, Snails and Slugs in the Home Garden. Foliar nematodes, which cause reddish brown areas between the leaf veins, can attack some ferns. Remove infected plants and destroy them. Do not put them into a compost pile. Check plants for pest problems before buying.

Quality garden centers carry a variety of ferns, generally in larger sizes than can be obtained through mail order. The mail order sources listed below stock many hard-to-find ferns.

Chuck Plemmons Perennials

275 South Blackstock Rd.

Spartanburg, SC 29301

864/576-1374

Hickory Mountain Plant Farm

148 Hadley Mill Rd.

Pittsboro, NC 27312

919/542-0360

Meadowbrook Nursery We-Du Natives

2055 Polly Sprout Rd.

Marion, NC 28752-7349

828/738-8300

Mountain Mist Nursery
10 Log Gap Rd.
Fairview, NC 28730

Native Gardens

5737 Fisher Ln.

Greenback, TN 37742

865/856-0220

Niche Gardens

1111 Dawson Rd.

Chapel Hill, NC 27516

919/967-0078

Plant Delights Nursery

9241 Sauls Rd.

Raleigh, NC 27603

919/772-4794

Sunlight Gardens

174 Golden Ln.

Andersonville, TN 37705

800/272-7396

Woodlanders, Inc.

1128 Colleton Ave.

Aiken, SC 29801

803/648-7522