POLYPODIUM. Polypody. A far-flung genus of ferns, inhabiting much of the Northern Hemisphere. They have creeping, usually branched rhizomes and fronds which may be undivided like those of the related Pyrrosia, or once-divided, seldom more. This gives them a distinctive appearance, less lacy than many ferns but still quite ornamental. Polypodies make pleasing displays among rocks and on walls, as they are seen in nature, and are adaptable to containers. A number of them are also quite tough, enduring drought either through summer dormancy or by virtue of thick, waxy fronds. If some are temperamental, it is in the direction of sensitivity to excess moisture or poor drainage. The following are easily grown in light to medium shade, with porous non-alkaline soil. Other details vary.
californicum. An attractive summer dormant species found on shady banks and cliffs nearly throughout the coast ranges of California. It has branched, creeping rhizomes, from which once-divided fronds about 1’ tall, bright green in color, rise in early fall, lasting into spring. ‘Sarah Lyman’ is a selected form with deeply cut fronds giving a fringed appearance. Once the fronds have died to the ground, little or no water should be applied until fall. Hardy to 10oor less.
guttatum. A Mexican species somewhat resembling our own P. scouleri. It has closely branched rhizomes which form dense, broad thickets in time. The fronds are thick and evergreen, growing 8-12" high, and only once-divided. It uses little water in spite of its subtropical appearance, and requires little maintenance. I am still not certain of its rock-bottom hardiness, though it has been unscathed by 20oF., with no direct frost.