This section is from the book "Commercial Gardening Vol2", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
A large and variable genus, now including Phegopteris, Goniopteris, Phymatodes, Drynaria, and other submerged genera. The most characteristic feature of the Polypodies consists in the roundish spore clusters being without any covering or indusium.
Of the 500 or more species known, P. (or Phlebodium) aureum, from Tropical America, is undoubtedly the most popular. It is largely grown for market, and is sold in pots of all sizes. The fronds are from 2-6 ft. long, pinnatifid, with wavy blue-green segments, on the under surface of which the spore clusters are arranged in two rows on each side of the midrib. It makes splendid specimens, and stands a good deal of rough usage. P. (Phymatodes) glaucum, from the Philippines, resembles some forms of P. aureum in texture and general appearance. Its fronds, however, are of a deeper blue-green tint, and the habit is somewhat more slender. The variety crispum is an elegant plant, but does not produce spores. P. aureum cristatum is a nice crested variety, and areolatum is a decorative form which may be recognized by having a single row of spore clusters. P. Mandaianum is a fine new variety, with blue-green deeply cut fronds.
Amongst the hardy Polypodies which are dug up in spring and sent to market are the Common Polypody (P. vulgare), with narrow evergreen fronds 6-12 in. long. There are several varieties of it, some being beautifully feathered and crested. The "Oak Fern" (P. Dryopteris) and the "Beech Fern" (P. Phegopteris) are also popular for hardy rock gardens and ferneries.