Polypodium interjectum Intermediate polypody

Polypodium cambricum x P. vulgare.

Epithet means "intermediate," referring to the plant's form. Evergreen, 12 to 18 in. (30 to 45 cm).Zones 5 to 8.

description: Intermediate between its two parents, this Polypodium is more robust than either parent. The rhizome is

Polypodium hesperium among rocks in the Cascade Mountains of Washington State.

The very attractive, nonreverting, fringed fronds of Polypodium glycyrrhiza 'Malahatense' emerge in late summer and remain cheerfully green throughout the winter.

Polypodium interjectum volunteering on a hedgerow in Wales.

creeping, branching, and covered with tan scales. Pale brown stipes with scattered rusty scales are one-third of the frond length. Unlike the blades of many polypodiums, the pinnatifid blades of this species tend to be somewhat oval. Eighteen to twenty-four pairs of bluish green to moss-green pinnae bear oval to circular, indusia-free imbedded sori, which appear as minute bubbles on the upper frond surface. New fronds unfurl in mid and/or late summer to fall, earlier than Polypodium cambricum and later than P. vulgare.

range and habitat: Look for this common species on walls and among rocks in Britain and Europe. It prefers humid and high rainfall sites with good drainage and slightly basic to neutral soil, rather than the acidic habitats of Polypodium vulgare.

culture and comments: This is an excellent candidate for crevices and nooks where the vivid greenery can relax the stark face of retaining walls, soften "functional rockeries," and add lively winter foliage to both. Keep newly planted vertical sites moist (a mossy dressing helps) until the fern roots reach the soil behind the structures. In general Polypodium interjectum differs from P. cambricum in having heavier textured, dull-surfaced, and narrower fronds. By contrast, it differs from P. vulgare by being larger, wider, and absent from acid soils. Martin Rickard (pers. comm.) suggests that a good basis for separating the three species is that P. cambricum is broadest near the base with the second pair of pinnae usually the longest giving the frond a narrow triangular outline; P. interjectum is broad est at or around the sixth pair of pinnae from the base giving the frond an oval outline; and P. vulgare has most pinnae in the lower half of the frond pretty much the same length, giving the frond a linear shape.

Polypodium polypodioides Resurrection fern Synonym Pleopeltis polypodioides Epithet means "looks like a polypodium." Evergreen, 4 to 10 in. (10 to 25 cm).Zones 6 to 10

description: The rhizome is long-creeping and branching. Stipes are a washed-out tan-green, grooved, and densely scaly as juveniles. They are just under one-half of the frond length. Pinnatifid blades are lanceolate to oblong-lanceolate with 10 to 15 pairs of blunt-tipped pinnae. The undersides are coated with gray peltate scales while, by contrast, the upper surfaces essentially have but a few. (Flora of North America [1993] transferred this species to Pleopeltis polypodioides based on these scales, and botanists in general agree that the entire genus needs further study.) Sunken sori without indusia are closer to the margins than midribs and are visible as minute nodules on the upper frond surface. There are six varieties.

range and habitat: In the southern United States, var. michauxianum coats host trees, especially live oak, Quercus vir-giniana, with massive swags of foliage forming canopies over the highways and woodlands looking like a primeval forest. in

Polypodium polypodioides gradually expands from an established foothold on the craggy bark of an oak tree in Florida. It will not harm the tree nor will the tree harm the fern.

Like many polypodiums, Polypodium scouleri grows naturally on native trees, in this example, the dead snag of the coastal spruce, Picea sitchensis. Populations in nature always hug the forests adjacent to the Pacific Ocean.

the northern portion of its range it is often found on rocks. The other varieties are natives of Mexico and Central America.

culture and comments: For years conventional wisdom presumed that these fern fronds curled in drought and heat to protect their upper surfaces from moisture loss and "resurrected" when watered. However, in his fascinating book, A Natural History of Ferns, Moran (2004) cites experiments performed in the 1920s by Louis Pessin demonstrating that in reality more water actually evaporates from the underside of the fern's fronds. So why expose them in times of stress? Using Polypodium polypodioides (which can lose up to 97 percent of its water without harm) as his subject, Pessin's experiments concluded that the protective scales actually absorbed moisture more rapidly during rehydration than the roots. Subsequently, researchers identified the process by which the water feeds back into the frond's cellular structure which becomes functional again in as little as 15 minutes. In the garden, away from its natural sites, the resurrection fern is not always so forgiving, but rather is challenging. offer it lean acid soil and good drainage. Firm it into place with moss and hope for the best.

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