Recent molecular work has indicated that this formerly much more diverse genus needed to be split into numerous segregate genera. The most important of these now close relatives that are no longer in the genus for gardeners are the genera Pleopeltis, Phlebodium, and Pseudophlebodium. We refer to all of these very similar ferns as “Polypody Ferns” here. The family Polypodiaceae is comprised of ferns that lack indusia. Indusia are shield-like or flap-like coverings over the developing sori. Like most garden ferns, Polypodium prefer a woodland habitat consisting of partial shade and well-drained but moist soil.
Polypodium Ferns (Polypody Fern)
Polypodium is a medium sized fern genus comprised of around 60 species, with a distribution that encompasses North and South America, Europe and western Asia as well as South Africa. The name Polypodium is derived from ancient Greek ‘poly’ for many and ‘podion’ for little foot which refers to the many knobby protuberances of the rhizomes. Polypodium are primarily evergreen ferns that can either be terrestrial (in ground), epiphytic (on trees), or epilithic (on rocks). Polypody have been used as herbs and edibles. The American Polypodium glycyrrhiza, whose roots have an intensely sweet licorice-like flavor, were chewed by native Americans and the roots of the European species have been used since Roman times as a flavoring for nougat and licorice candy. Polypodium is generally a fern genus for cooler locales (northern US and continental Europe), but we have assembled a collection that includes ferns with good heat and humidity tolerance. When you're ready to buy Polypody ferns for your perennial garden, check out our online offering for sale.
Polypodium appalachianum (Appalachian Rock Cap Fern) This is the larger and more luxuriant of the two common rockcap ferns found in the Southern Appalachians. It can be told from the more widespread Polypodium virginianum by the longer leaves that are wider towards the base and often long tapered tip to the frond. Appalachian Rock Cap Fern is a diploid species and is one of the two species involved in the original speciation of the Common Rockcap Fern (P. virginianum); the other parent is apparently Polypodium sibiricum, which is not found anywhere near P. virginianum today! Just another case illustrating that nativity is a period in time of a place and not permanent. This beautiful species is found festooning mossy boulders, ledges, and cliff faces often near or where there is seasonal seepage. Though they would be beautiful in a garden setting, this species is difficult to grow in the hot, humid Southeast away from the mountains. If you’re lucky enough to live in a cooler climate this can be a beautiful rhizomatous species to establish on mossy boulders. (Hardiness Zone 4a-7b)
Polypodium glycyrrhiza (Licorice Fern) The Licorice Fern is emblematic of the humid forests of the Pacific Northwest where it is most abundant as an epiphyte on nearly every tree that has a suitable surface. It even colonizes rooftops and virtually any surface that stands still. The rains are concentrated during the winter months and Licorice Fern has adapted to this by producing fronds that emerge in the autumn with rain and go dormant during the dry season (summer). We have only been successful with a small number of cultivars here in the Southeast for a season or two, but if you live in the great Pacific Northwest, you likely have this fern that we covet and plenty to spare. (Hardiness Zone 5a-8b)
Polypodium glycyrrhiza x scouleri (Hybrid Licorice Fern) While we have been unsuccessful in maintaining either parent for longer than a season or two, this hybrid between two US west coast natives has proven to be vigorous in our woodland garden. We haven’t had this one going for long but if it continues to be as good as it has been the past couple of seasons, we will look to offer this in the future. Expect a robust plant with 12-18” long leaves held nearly vertical to slightly arching and nearly intermediate in appearance with the two parental species. (Hardiness Zone 7b-9b, guessing)
Polypodium guttatum (Mexican Polypody) Well, if the more northerly polypody ferns don’t grow well for us, why not try something a little more southern? At least that’s what we’re thinking. This species hails from Mexico where it grows in typical polypody fern habitats (boulders, ledges, and cliffs). It has proven more adaptable to growing in typical partially shaded rock garden conditions and though we haven’t grown this species here long, it has proven to be both cold hardy and vigorous! We will keep you updated on how this adorable little evergreen fern with fronds that reach 1’ in length does. (Hardiness Zone 7b-9b, guessing)
Polypodium hesperium (Western Polypody) Though the range is similar to the difficult to grow Licorice Fern, this western US native has proven fairly reliable in our shaded rock garden where it is growing in well-drained but evenly moist soil. In appearance it resembles our eastern Common Rockcap Fern but may have more adaptability in the garden. In the wild we have seen this species growing in shallow soil of slopes, mossy boulders, ledges, and cliff faces. It is native from British Columbia south to California and also in the Rocky Mountains from New Mexico to Canada. (Hardiness Zone 5a-8b)
Polypodium virginianum (Common Rockcap Fern) This species is widespread in eastern North America where it can be found on boulders, ledges, cliff faces and even sometimes on logs or bases of trees. Though it is abundant over a wide area it is notoriously difficult to establish in the garden. If you try this pretty little fern, make sure you don’t let it dry out during establishment. It is confusingly similar to the Appalachian Rockcap Fern (see discussion above). (Hardiness Zone 3a-8a)
Polypodium vulgare 'Ulleung Island': (Ulleung Island Common Polypody) This Polypodium species is common in Europe and Asia, but I have consistently failed with the European forms in our hot humid summer. I have, however, been quite successful with this form that I found in 1997, growing near the village of Nari on the Korean island of Ulleung. Our ten-year-old patches are now 3’ wide. The 6” tall medium green evergreen leaves, which look as good in January as they do in June, form a thick patch above the slowly spreading rhizomes. This is a fantastic fern that needs to be grown in all woodland gardens. (Hardiness Zone 5a-8b)
Phlebodium is a small genus of three species of rather large ferns with pinnately lobed but not divided fronds that are nearly confined to the tropics. The single species native to the United States is the Golden Polypody (Phlebodium aureum) which is hard to miss if you’ve traveled to Florida where it often sports its 2’+ long fronds from the boots of palmettos.
Phlebodium pseudoaureum (aka: Polypodium areolatum) In case you've never heard of a Phlebodium, it was kicked out of the more familiar genus Polypodium over reproductive issues. This species is found in tropical and subtropical regions of North and South America. We got our first plant from our friends at Yucca Do, who were excited about its winter hardiness. After several years of trialing, we are as equally excited. The 1' tall glaucous leaves, which look more like a snow mitt than a fern frond, emerge from the slowly spreading, red-haired rhizomes that lay on top of the soil. Although Phlebodium pseudoaureum will grow in a wide range of soil types, slightly moist soils and a sloping site are best. (Hardiness Zone 8a-10b)
Pleopeltis michauxiana aka: Polypodium polypodioides (Resurrection Fern) Giant Live Oak trees festooned with Spanish Moss (Tillandsia usneioides) and Resurrection Fern are emblematic of the American South. Pleopeltis michauxiana is found epiphytically in the Deep South and also occasionally on trees in more inland areas. In the piedmont and mountains of the South, it is also often found growing on rock, particularly those high in magnesium or calcium, such as limestone and amphibolite. This US native is perfect for the shady rock garden where it can grow epiphytically on trees, rocks, or old rotten logs. Resurrection fern spreads via a short branching rhizome to make a nice patch but is never invasive. The dwarf 4-6" long evergreen fronds resembles a miniature Christmas fern with the lower side of the frond covered with rusty colored scales. The term ‘evergreen’ needs to be qualified since when dry, this species employs the strategy of losing most of its water, the leaves curl up, and appear dead. Once the humidity is high and they regain water, they spring right back to life (resurrected). Plants that go into near stasis or stasis when dry and spring back to life when exposed to water are termed true xerophytes and many desert ferns employ the same strategy. This species can be difficult to establish and should not be allowed to dry out at all during the first several weeks. Pleopeltis michauxiana does not like high fertility, so back off the fertilizer. (Hardiness Zone 6a-10b)
Pleopeltis is a larger genus consisting of over 100 species found throughout the Americas, Africa, and India. Most of the species are tropical. These ferns are typically epiphytic (on trees) or epilithic (on rocks) and are represented by a single species in the temperate regions of America (Pleopeltis michauxiana). In contrast to the true Polypodium ferns, these are mostly suited to cultivation in warmer climes. One of the most exciting new ferns introduced by Yucca Do Nursery are the excellent selections of Pleopeltis lepidopteris.
Pleopeltis lepidopteris ‘Morro dos Conventos’ (Morro dos Conventos Brazilian Hairy Sword Fern) This is a fern we didn't even know existed before 2010! Pleopeltis lepidopteris has quickly become one of our favorites. This sun-loving epilithic (rock grower) fern hails from the sandy, acidic coastal (restinga) habitats in southern Brazil (Rio Grande du Sul). This offering is a Yucca Do Nursery find from a disjunct population along the beach in Morro dos Conventos, Brazil. The 18" tall x 2" wide, rigidly upright fronds emerge covered in thick silver hair, to which some of us can now relate. As the fronds age, the hair thins, and the green leaf surface becomes more visible. Pleopeltis lepidopteris spreads slowly from surface rhizomes. We've grown this evergreen Pleopeltis in our rock garden since 2012, where it has thrived even through winter temperatures of 7 degrees F. In extremely hot climates, part sun to light shade might be best. (Hardiness Zone 7b-9b)
Pleopeltis lepidopteris ‘Arroio dos Ratos’ (Arroio dos Ratos Brazilian Hairy Sword Fern) This is another selection of the remarkable Brazilian Hairy Sword Fern that was shared with us by Yucca Do Nursery. This collection hails from Rio Grande do Sur. Though similar to ‘Morro dos Conventos’ this one is smaller in all respects. We suspect that it may be a diploid while ‘Morro dos Conventos’ is likely a tetraploid, but this requires more research by an interested collaborator. Cultivation requirements are identical for both cultivars and we suspect the winter hardiness is similar, but we have only grown this one through 8 rather warm winters so far. (Hardiness Zone 7b-9b, guessing)