Plant Profile: Thelypteris (Maiden Ferns)

Plant Profile: Thelypteris (Maiden Ferns)

or the genus formerly known as Thelypteris

By and Published February 07, 2023

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A huge group of ferns known collectively as Maiden Ferns have traditionally belonged in the genus Thelypteris. Most of the species are confined to the tropics but there are a number of familiar and beautiful species that extend well into cooler climates. The name Thelypteris is derived from the Greek thelys meaning female, and pteris, for fern. These ferns tend to be of small to medium in stature, rhizomatous and most are deciduous with thin leaves. The spores tend to be produced in lines on the undersides of the fronds and the bases of the plants lack the dark scales prominent in other typical ferns such as Dryopteris or Polystichum and instead are often covered with tiny soft hairs. Of course, as we have gotten to know the actual genetic relationships of the 1190 species once lumped into this group, taxonomists have realized that they are not all closely related. In fact, the taxonomy of the group has been changing at warp speed. As an example, during the two years spent writing and awaiting publishing of the Guide to the Wildflowers of South Carolina, the appropriate name for the popular New York Fern changed from Thelypteris noveboracensis to Parathelypteris noveboracensis and then just after the final editorial touches were done it was reassigned yet again to the genus Amauropelta. The name has changed more rapidly than the editing process.

The true genetic relationships are becoming clearer and, as proponents of the science of taxonomy, we are presenting the species which we grow here along with their current (as of 2022) status and names. In horticultural circles many of these ferns have been long known by their name under the genus Thelypteris and, for the ease of finding them online and in our catalogue, we largely still list them that way with their current accepted genus given in the description.

Species still in Thelypteris

Thelypteris palustris (Marsh Fern) The genus Thelypteris as recognized today contains only two species, this species and T. confluens which is found mostly in the southern hemisphere and both species are known as marsh fern. Thelypteris palustris is the type for the genus-being the first one to receive a name. Two varieties of this circumboreal (ranging across the northern hemisphere) species exist. Variety palustris is the Eurasian variety while var. pubescens is native to North America and eastern Asia. This small, strongly rhizomatous fern forms large, dense masses in open, sunny moist soils (marshes). Marsh Fern has the stature of New York Fern, but the fronds are not strongly narrowed towards the base. It is very useful in the landscape for problematic low, sunny wet areas where it can spread to its heart’s content but does not make a particularly good garden subject due to its aggressively spreading nature. (Hardiness Zone 3a-9b)

Amauropelta

233 of the former species of Thelypteris are now in the genus Amauropelta which is largely tropical with a handful of notable and extremely garden-worthy exceptions.

Amauropelta beddomei ‘Korean Traveler’ = Thelypteris boddomei (Korean Maiden Fern): The Asian equivalent of the US native, Thelypteris noveboracensis. This marvelous deciduous fern makes an elegant groundcover to 6' wide in 4 years, admired by large numbers of our garden visitors. The 18" tall by 3" wide, finely cut, light-green fronds are held upright on the creeping rhizomes. Our offering comes from spores collected on Korea's famed Cheju Island. (Hardiness Zone 6a-9b, guessing)

Amauropelta glanduligera ‘Green Shag’ = Thelypteris glandulifera (Green Shag Chinese Gland Fern) This is a 2014 PDN/JLBG introduction of the virtually unknown, deciduous species from a 2005 Hans Hansen collection from Guizhou, China. In the garden, ‘Green Shag’ has formed a 2’tall x 6’ wide desne patch in 8 years. The fronds are incredibly densely arrayed, light green and upright. This is truly a superb weed-proof groundcover. We have found that it thrives in full sun (where growth is faster) as well as shade. We can’t recommend this highly enough! (Hardiness Zone 7b-9b, at least)

Amauropelta noveboracensis = Thelypteris noveboracensis (New York Fern) New York Fern is a beloved woodland species native from Maine south to Louisiana. Among our native species of deciduous ferns, it is easily distinguished by the unique outline of the frond—it narrows towards the tip and towards the base, like a miniature Ostrich Fern. One might say it burns the candles at both ends, just like a New Yorker! It is one of the finest groundcovers for the shaded garden. New York Fern is an easy-to-grow rhizomatous fern that can produce large patches, 5' wide in 5 years if grown in rich moist soil. The fronds are generally less than a foot tall. Though it spreads it does not tend to form dense patches and is unlikely to smother other desirable woodland species. The light green airy fronds give a lacy look to the garden. (Hardiness Zone 3a-8b)

Christella

Christella acuminata = Thelypteris acuminata (Acuminate Fern) Strangely absent from most fern reference books, this is an easy-to-grow garden fern that performs wonderfully in a moist woodland garden. The 15" tall light green fronds stand upright, while the underground rhizome spreads to form a 6' wide clump in 5 years. We grow a wild form as well as a charming crested form ‘Cristata’. (Hardiness Zone 7b-9b, at least)

Christella dentata = Thelypteris dentata (Downy Maiden Fern) This Asian native has naturalized in warm temperate and tropical climates around the world where it can often be found growing from the mortar of old walls and other such alkaline places. It has naturalized in the Carolinas but does not become noxious in natural areas. In our trials, this has proven to be a great upright garden specimen with short rhizomes that does not spread to form the aggressive monocultural patches of other species. We grow two forms, one from a naturalized population in Jasper County, SC and another from wild collected spore from Vietnam given to us by acclaimed plantsman Ozzie Johnson. Its narrow, fuzzy, light-green fronds with dark brown to black stipes (stems) and vertical stature allow it to be used among other plants without eating them alive. While it prefers moist soils, our dry acidic sand has suited it just fine. This one will thrive in shade or sun. A close relative, Christella hispidula has a similar growth form but lacks the dark stipes and has more finely divided leaves and is native (or adventive) in similar sites in the Carolina coastal plain. (Hardiness Zone 7b-10, at least)

Coryphopteris

Coryphopteris japonica ‘Cheju Gem’ = Thelypteris japonica (Cheju Gem Japanese Maiden Fern) This remarkable little clump forming fern was collected by us from Cheju Island in Korea during our 1997 trip. It is related to the bog-dwelling Massachusetts Fern found as a very rare native in a few of our high mountain bogs. It spreads slowly from creeping rhizomes to form a 1-1.5’ tall clump that is 3’ wide in 5 years. The elegant, lacy light green leaves are 12-15” tall and it forms a dramatic and beautiful patch making it one of our most favorite new ferns. (Hardiness Zone 6a-9b, at least)

Macrothelypteris

Macrothelypteris torresiana ‘Eco Maiden Lace’ = Thelypteris torresiana  (Eco Maiden Lace Mariana Maiden Fern) Macrothelypteris means a macro (huge) thelypteris and that describes this species well. This Don Jacobs selection of the easy-to-grow plant has proven to be much more winter hardy than our Bermuda collection. For us, Macrothelypteris torresiana 'Eco Maiden Lace' makes a deciduous 3' tall clump of exceptionally cutleaf foliage...much more divided than other forms we have grown. It provides a splendid airy texture among bold textured shade plants such as Hosta. A note of caution, this non-native species has been naturalizing aggressively in more southerly areas and has been discontinued here at PDN. (Hardiness Zone 7b-10, at least)

Metathelypteris

Metathelypteris glandulifera = Thelypteris bombadilii (Bombadil’s Fern) Metathelypteris is a small genus of 17 species found in Asia. This species was not explicitly treated in the most recent update on the genus but belongs in the genus Metathelypteris. It hails from southeastern China. Bombadil’s Fern makes a superb deciduous groundcover spreading to 5’ wide in 10 years. The 22” tall, mostly upright fronds form a lovely patch which resembles a thicker-leaved and darker green New York Fern. As with most spreading ferns it can overrun small neighbors like Asarum or Epimedium but works great among larger woodland perennial and shrubs. (Hardiness Zone 7b-10, at least)

Pelazoneuron

Pelazoneuron kunthii = Thelypteris kunthii (Kunth’s Maiden Fern or Southern Shield Fern) This robust fern is one of our favorite southeast natives and is one of the most spectacular ferns we grow. It is native to the coastal plain of the Carolinas where it can be found in soils that have an abundance of calcium and are circumneutral in reaction though it grows quite well in our acidic sandy loam soils. This species appears to be expanding its range all by itself and Patrick McMillan has even recently discovered a population growing on rocks near the edge of Lake Jocassee in the Blue Ridge escarpment of South Carolina. The large fronds of light green, can reach 30” in length and are produced all summer, contrast nicely with the pale stipes (stems) that support them. The slowly rhizomatous clumps spread nicely to make incredible dense woodland masses. Do not expect this species to be an early riser in the garden where it often doesn’t produce new fronds until late April or May. (Hardiness Zone 7a-10, at least)

Pelazoneuron ovatum var. lindheimeri 'Austin City Limits': (aka: Thelypteris ovata var. lindheimeri A2T-025) This wonderful but virtually unknown deciduous fern is closely related to Thelypteris kunthii. It has more narrow pinnae and strictly upright 2' tall by 6" wide, light green fronds that form a very attractive and dense patch (5' wide in 5 years). This has become one of our favorite and most durable garden ferns and can be grown in shade to full sun. The variety lindheimeri is restricted to TX in the USA but the more widespread var. ovata occurs naturally on limestone in the Carolina coastal plain. (Hardiness Zone 7a-9b, possibly colder)

Pelazoneuron ovatum var. lindheimeri 'Weekend at Boerne' = Thelypteris ovata var. lindheimeri A3T-028 (Weekend at Boerne Lindheimer’s Maiden Fern) During a weekend at Boerne (pronounced "Bernie"), Texas, I stumbled upon this stunning form of maiden fern growing along the edge of Wasp Creek. Unlike the 24" tall form we already grew, this gem reached 3' tall with upright but elegantly arching, light green fronds. We grow this slowly stoloniferous fern in dry sand, showing that it thrives in a wide range of conditions. (Hardiness Zone 7a-9b, possibly colder)

Phegopteris

Phegopteris connectilis ‘Emei Shan’ = Thelypteris phegopteris (Emei Shan Northern Beech Fern) We couldn’t have been more surprised to find a heat-tolerant form of this far northern species! Our plants are from a 2012 Mark Weathington collection from the magical Emei Shan in China. This tiny fern with triangular fronds no more than 6” high will slowly spread to form a loose colony in the garden. It’s super cute. The species is generally found across the northern hemisphere at high latitudes — only a few populations make it to the southeastern United States where they are often found in cool, dark microclimates at high elevations. This selection has proven as tough as nails in our hot, humid summers in the woodland garden. (Hardiness Zone 3a-8a, at least)

Phegopteris hexagonoptera = Thelypteris hexagonoptera (Broad Beech Fern) This is a marvelous native that forms a slowly deciduous spreading patch.  The upright stipes are often black, contrasting nicely with the triangular leaf blade. It has proven quite easy to grow and durable in average to moist soils. (Hardiness Zone 5a-9a, at least)

Phegopteris taiwaniana = Thelypteris decursive-pinnata, in part (Japanese Beech Fern) Japanese Beech Fern is an unusual, but very easy-to-grow fern with narrow, coarse-textured fronds that have an upright growth habit. The clump spreads slowly, eventually to a large mound. Though the leaves are narrow and elongate this is a relative of our more triangular-leaved American beech fern species. Recent research by Fujiwara et al. (2021) has indicated that what was previously known as a single species is now several. The diploid species with confluent bases to the pinnae lobes, somewhat evergreen with pointed tips to the pinnules and leaves widest at the middle is now referred to as P. taiwaniana. The tetraploid plants that are not common in cultivation are referable to true P. decursive-pinnata. (Hardiness Zone 4-8, at least)

Pronephrium

Pronephrium penangianum = Thelypteris penangiana (Chinese Peng Fern) One of the most amazing tropical-looking ferns and one of the most exciting we’ve grown in quite a while. The prehistoric looking 5’ long simple pinnate fronds emerge from a creeping rhizome that forms a 6’ wide patch in 10 years. This deciduous species hails from forested streamsides from 3.000-10,000’ elevation, from Kashmir through south central China. Our results in both moist and average moisture garden sites have been equally good. This very distinctive fern is also used medicinally in China to treat irregular menstruation. Our selection ‘Jurassic Park’ is a particularly nice and robust form. (Hardiness Zone 7a-9a, at least)
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