Ferns evolved about 360 million years ago, and there are now some 12,000 species. While of minor economic importance, many fern species are cultivated around the world as ornamental garden and houseplants. Most cultivated ferns are forest species that grow in low-light conditions on the humid forest floor. They are easy to cultivate as houseplants provided every effort is made to replicate this environment.
While ferns require plenty of water and damp compost, they are vulnerable to root rot if waterlogged. Place potted ferns on a saucer full of water but keep the base of the pot above the water level with small pebbles. Water your fern as soon as the surface of the compost starts to dry out. Ferns require high humidity, which must be maintained indoors with regular misting--mist every other day for the best results. Use rainwater or distilled water to mist and water ferns; they do not like the minerals or chlorine in tap water.
Fertilize potted ferns once a month with a liquid fertilizer formulated for houseplants at half the recommended strength. Most fern species have a growing season that runs from spring to autumn and do not need to be fertilized during the winter.
As forest plants, ferns do not need high light levels, and direct sunshine will dry them out and damage their foliage. A north-facing window is ideal for most species. Rotate your plant every two weeks to keeps its growth even. Keep ferns away from cold winter drafts and the hot, dry air produced by heaters.
Most fern species grow in slightly acidic soils that are rich in organic matter and free-draining. The closest available substrate to this is a soilless, peat-based compost.
Ferns are easy to propagate by dividing large plants in spring. Each new plant should have several leaves and a clump of roots or tubers. Plant each division in a pot with the roots 1 inch below the soil surface and water well. Place the pot in a cool, well-lit place such as a windowsill out of direct sunshine. Keep the soil wet but do not fertilize for six months.
Potted fern plants are vulnerable to infestation by scale insects and mealy bugs. Mealy bugs are best treated with a houseplant insecticide spray applied every 10 days for a month. Scale insects require treatment with a systemic insecticide, because their scales make them resistant to sprays. Low-level infestations of both scale and mealy bugs can be treated by painting the pests with a paintbrush dipped in rubbing alcohol.