Plant Profile: Polystichum - Shield Ferns

Plant Profile: Polystichum - Shield Ferns

A Fern of the World

By and Published January 24, 2023

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Ferns in genus Polystichum are commonly called shield ferns because of their indusia (which is a flap that covers the clusters of spores) that is attached like an umbrella or shield; the clusters of spores look like little shields when covered by the indusia. The name Polystichum is derived from the Greek polys (many) and stichos (row) as the sori are placed in multiple rows.

In our area (North Carolina), most people with any native plant interest at all know the common evergreen Christmas fern (Polystichum acrostichoides) so it would be tempting to call all the species Christmas fern, but alas, that name is reserved for our local native.

Polystichum is a large genus that consists of about 260 species distributed across the world. China (with 120 species) and Mexico to Brazil (100 species) are the primary areas of diversity for the genus. The evergreen fronds tend to have a thick, rough texture. The Korean rock fern, Polystichum tsus-simense is a food source for some butterfly species. As a rule, this genus prefers well drained soils that are high in organic matter and will suffer from winter crown rot where it is too wet. The genus Polystichum is in the midst of a tug of war with the genus Cyrtomium for its species composition. Because some Polystichum, like Polystichum lepidocaulon, are closely allied to Cyrtomium, many taxonomists have proposed to merge the two genera under Polystichum. We respectfully disagree and will keep the two genera separate.

Polystichum Varieties

These are a few of our favorite varieties of shield fern.

Polystichum acrostichoides (Christmas Fern) Christmas fern is a wonderful, easy-to-grow US native (Minnesota south to Florida) with sturdy, dark evergreen fronds emanating from a central point, making a 1’ tall x 2' wide clump...particularly effective when used in drifts. The fronds first emerge upright, then flatten with age. The tips of each frond that bears the spores narrows dramatically towards the tip with the fertile pinnules much narrower than the lower sterile ones. The name Christmas fern probably comes from the tradition of collecting the evergreen greenery at Christmas time for decorating but if you look at each pinnule they also have the shape of a Christmas stocking, or some say Santa’s sled. Christmas fern is one of the finest of all evergreen ferns and even retains its attractive appearance all winter...simply superb for woodland gardens, especially those with deep shade areas! A PDN selection ‘Raven Cliff Crested’ is a superb, crested form of this beautiful fern. (Hardiness Zone 4a-9b)

Polystichum aculeatum (Hard Shield Fern) This easy-to-grow, evergreen European native is not to be ignored by those of you in colder temperate climates. It is a naturally common in cool and cold places like the British Isles. Although it prefers damp, alkaline soils, it has fared surprisingly well in our hot and humid climate in fast draining, amended sand. The elegant 3' wide by 2' tall clumps are composed of 2' long, narrow, glossy dark green, upright fronds that are hard to the touch unlike its look-alike, Polystichum setiferum, the soft shield fern. (Hardiness Zone 4a-7b)

Polystichum braunii (Braun’s Shield Fern) This elegant, small New England and upper Midwestern US and European native makes a wonderful semi-evergreen clump 18" x 18”, with ruffled edges on lustrous dark green foliage. It is very popular in gardens in the Northeast US. Though it is found far to the north of our area, it has performed well in our woodland gardens under standard conditions, as long as drainage is good, and it is not allowed to dry out. Perfect for the shady rock garden. (Hardiness Zone 3a-8b)

Polystichum × dycei (Dyce’s Shield Fern) This wonderful evergreen fern is a hybrid of the Australian Polystichum proliferum and the Eurasian-American Polystichum braunii. It produces robust-growing clumps to 2' tall x 3' wide. The clumps are composed of sturdy, 30" long, slightly arching, dark green fronds, which in fall produce proliferous bulbils, which will lead to new plants, on the top and end of the fronds. (Hardiness Zone 4a-7b, at least)

Polystichum lepidocaulon (Whipcord Eyelash Fern) We have been fascinated by this strange fern, shared with us in 2003 by pteridomaniac Judith Jones. Hailing from mountainous rocky cliffs, in Japan, Korea, and China, the 30" wide x 15" tall evergreen specimens are composed of glossy, holly fern-like leaves. The graceful, yet glossy, tropical appearance of this species makes it one of the finest foliage plants for the woodland garden. One of the unique attributes of Polystichum lepidocaulon is the terminal pinnae which morphs into a 2' long whip-like tip that extends outward where it eventually roots down to form a new plantlet—just like the unrelated Walking Fern (Asplenium rhizophyllum). As mentioned earlier, this species resembles a Cyrtomium species (holly fern) and is of uncertain placement in this genus. (Hardiness Zone 6b-9b at least)

Polystichum luctuosum (Sorrowful Fern) is a lovely small fern that's closely related to the popular Polystichum tsus-simense and Polystichum mayebarae. In fact, the only difference is that the fronds of Polystichum luctuosum are divided twice instead of three times. In the wild, sorrowful fern can be found along streams, often growing on alkaline rocks between 2,000' and 6,000' elevation in Japan, Korea, China, and, yes, South Africa. Polystichum luctuosum forms a 1' tall x 2' wide evergreen clump of finely divided silvery-green fronds. Slightly moist to average soil moisture is best. (Hardiness Zone 6a-8b)

Polystichum makinoi (Makino’s Shield Fern) Native to forested mountains in China and surrounding countries, Polystichum makinoi is an attractive evergreen clumper. Dr. John Mickel, author of "Ferns for American Gardens," writes, "This is one of my favorite holly ferns." We concur, 10 times that, and can't imagine why any shade gardener wouldn't plant these en masse. This vigorous grower forms a 2' tall x 2' wide compact rosette of dark, glossy green fronds. (Hardiness Zone 5a-8b)

Polystichum monticola (Mountain Shield Fern) Polystichum monticola has been a nice surprise in our garden, being one of the few native South African ferns we grow. The Mountain Shield Fern hails from Kamiesberg (Northern Cape), KwaZulu-Natal, Lesotho, and the Free State, where it can be found in rock crevices at 2,000-3,000' elevation on the edge of evergreen forests, which go through both a moist and dry period. In our garden, it has the appearance of Polystichum setiferum forming a compact 1' tall x 20" wide lacy, evergreen excellent, but little-known fern. (Hardiness Zone 7b-8b)

Polystichum neolobatum (Asian Saber Fern) Polystichum neolobatum has a wide range in eastern Asia. This fern will tolerate extreme summer heat and is fairly drought resistant when established. Polystichum neolobatum is without doubt one of the most elegant ferns in cultivation forming a v-shaped, evergreen, 20” tall x 2’ wide clump of stiff, almost sharp-edged, deep green, glossy foliage. We have found that Polystichum neolobatum grows much better when sited on a slope and grown in well-drained, but slightly moist soils. (Hardiness Zone 6a-7b)

Polystichum polyblepharum (Korean Tassel Fern) The Korean Tassel Fern is native to Korea and Japan. The dark, evergreen, plastic-like foliage arches out from a central crown, forming a 1’ tall x 2’ wide clump. Each frond is a lacy, artistic masterpiece. The species name "polyblepharum" means "many eyelashes". (Hardiness Zone 5b-9b, at least)

Polystichum retrosopaleaceum (Narrow Tassel Fern) This easy to grow evergreen Japanese native bears a striking resemblance to one of our other favorite ferns, Polystichum polyblepharum, except that the fronds are narrower, particularly toward the base. The giant crown is home to 3' long glossy dark green fronds that arch out around the center. Polystichum retrosopaleaceum prefers a moist site in the woodland garden. (Hardiness Zone 5a-9b)

Polystichum rigens (Rigid Shield Fern) This native to China and Japan is a cute, small, evergreen clumping fern with fronds that are wider in outline than many other Asian Polystichum. The pinnules are deeply serrate-toothed and often transition from light green in spring to dark green in summer, and golden green in winter. Quite resilient in our trials and developing more golden winter color in more open shade or edges of woodland gardens. (Hardiness Zone 5a-8b, at least)

Polystichum setiferum (Soft Shield Fern) This European native is one of the most available commercially grown fern species, with over 300 named cultivars. Polystichum setiferum makes an attractive 2' wide x 1' tall evergreen clump of lacy fronds for us but should double that size in a cooler summer climate. Many of the cultivars are too similar to tell apart without a label, so we are only mentioning but a few that are easily obtained. (Hardiness Zone 5a-7b)

Polystichum setiferum 'Divisilobum' (Divided Lobe Soft Shield Fern) This selection of soft shield fern has very dissected foliage giving it a very lacy appearance. The arching growth habit makes a mass planting in the woodland look truly spectacular! (Hardiness Zone 5a-8a)

Polystichum setiferum 'Herrenhausen' (Herrenhausen Soft Shield Fern) This German selection of the semi-evergreen Southern European native Soft Shield Fern is a particularly narrow-leafed form. Polystichum setiferum 'Herrenhausen' makes a 30" wide x 18" tall clump of soft, lacy green foliage. Although they prosper on the west coast, we have not been particularly successful in the Southeast. (Hardiness Zone 5a-8a)

Polystichum setiferum 'Plumosomultilobum' (Multi-lobed Plumose Soft Shield Fern) (aka: P. setiferum 'Plumoso-densum') This unusual form of the semi-evergreen soft shield fern makes a 14" tall x 18" wide clump, composed of very finely divided fronds resulting in a very lacy appearance. When grown well, Polystichum 'Plumosomultilobum' will form small viviparous (without the benefit of meaningful sex) plantlets on the leaf in October and November. This has been one of only a few Polystichum setiferum cultivars to thrive in our hot, humid climate. (Hardiness Zone 5a-7b)

Polystichum setiferum 'Rotundatum Cristatum' (Round Cristate Soft Shield Fern) This cool selection has rounded pinnules and uniquely branching 20" fronds. Additionally, tiny extraneous plantlets will form along the frond when the plants are mature. Slightly moist and near neutral soils are preferred. (Hardiness Zone 5a-7b)

Polystichum tagawanum (Tagawa’s Shield Fern) A very cold-hardy, evergreen shield fern named for Japanese botanist Tagawa. This species hails from Japan where it is found in forests on mountain slopes. It has an erect rhizome that forms a clump with fronds that can reach 30” or more in length in cooler climates and are 2-pinnate appearing like a lacy Christmas fern. It has done well in our climate but looks much more robust farther to the north. (Hardiness Zone 4a-7b, at least)

Polystichum tripteron (Trifid Shield Fern) Polystichum tripteron is a robust grower that hails from moist mountain woodlands in China, Taiwan, Japan, and Korea. In the garden, Polystichum tripteron forms a very attractive, 2' wide, deciduous clump of medium-green fronds. The basal pair of pinnae are much longer than the other pinnae resulting in unusual fronds that look like wings on a green airplane. Although this has performed well for us, it really prefers cooler summers. (Hardiness Zone 5a-8a, possibly colder)

Polystichum tsus-simense (Korean Rock Fern) This Asian native is an easy-to-grow small fern for the woodland garden. The dainty, little, semi-evergreen fern features dramatic black stems that contrast with the rich green, pinnate foliage. Korean rock fern makes a tight clump that arches out and downward, eventually to 15" wide. (Hardiness Zone 6a-8b)

Polystichum tsus-simense var. mayebarae (Mayebara’s Shield Fern): Polystichum tsus-simense v. mayebarae makes a 1' tall by 2' wide clump of very dark evergreen cutleaf pinnae on 15" long arching fronds...about 1/3 larger than typical Polystichum tsus-simense. We have found this quite easy to grow in moist or dry shade. (Hardiness Zone 6a-8b)

Polystichum 'Spiny Holly' (Spiny Holly Shield Fern) From China comes this unusual evergreen Polystichum species that has yet to be positively identified. Judith Jones, of Fancy Fronds, gave it the cultivar name Polystichum 'Spiny Holly', which has been mistakenly written P. 'Shiny Holly' in other catalogs. What we know is that it is similar to Polystichum neolobatum but much more adaptable to hot humid summers. Polystichum 'Spiny Holly' makes a splendid, 18" wide clump of very thick, glossy fronds. The edge of the fronds are so stiff that they appear to have tiny spines. (Hardiness Zone 6a-8b, at least)

Polystichum xiphophyllum (X Shield Fern) Another of the wonderful but overlooked Chinese ferns that I won't garden without. The X shield fern makes an 18" wide, evergreen, perfectly symmetrical mound of upright, stiff, artificial-feeling fronds. Perhaps the most wonderful attribute is it gives you a fern species which begins with the letter X! (Hardiness Zone 6a-8b, at least)

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