Ferns generally require rich, moist soil with extra organic matter. Some require a drier, less-fertile soil. If ferns haven't done well for you in the past, have your soil tested by your local extension service or a soil-testing lab to determine soil fertility and pH. Some ferns are extremely fussy about pH.
For large and medium-sized ferns, dig the planting area deeply (at the very least, turn the soil to a spade's depth). Plant smaller ferns such as Japanese painted fern as you would any perennial. Sprinkle on organic fertilizer, if needed, when you add soil amendments. For more on organic fertilizers, see the Fertilizers entry.
Buying And Planting Ferns
Garden centers offer a few ferns, but you can find more through nursery catalogs and Web sites that specialize in perennials, shade plants, or ferns. No matter where you buy, make sure plants are nursery propagated, not collected from the wild. Large plants at low prices usually mean wild-collected plants. Don't be afraid to ask for the vendor's sources.
Plant ferns in fall or early spring. Garden-center plants will be potted, but mail-order plants are likely to arrive bareroot. Remove potted plants from their containers, cutting the plastic if necessary. Very carefully score the root ball with a sharp knife. Make 3 to 5 shallow cuts lengthwise down the root ball. This breaks up the solid mass of fibrous roots that often forms along the container wall. Plant the fern at the same level at which it was growing in the pot. Planting too deeply will kill plants with single crowns.
Set bareroot plants with creeping rhizomes (underground stems that produce both roots and fronds) 1/2 to 1 inch below the surface. Large rhizomes can be planted deeper. Set single-crowned ferns like osmundas and ostrich ferns with the crown above soil level. Place the upper part of the rhizome above the soil surface, with the crown 3 to 5 inches above the soil, depending on the plant's size. Finally, don't plant too thickly, since most ferns spread rapidly.
Ferns are a carefree group of plants. Mulch with shredded leaves or bark to help control weeds and conserve moisture. Ferns never need staking, pinching, or pruning. You may have to remove an occasional damaged frond, but that--and watering during dry periods while the plants are getting established--about sums up the care requirements for ferns during the growing season.
Each spring, remove last fall's leaves from the fern bed, shred them, and return them to the bed. Clear the bed early to avoid damage to emerging fiddleheads. Don't rake the beds, or you may damage crowns and growing tips. You won't need fertilizer if you leave the mulch to rot into the soil.