Cystopteris

More Information About Cystopteris

When it comes to great living mulch for the shade garden, few plants can beat the delicate, small-statured, creeping deciduous masses of Cystopteris. Most species creep along at or just below the surface of the soil without forming impenetrable masses and easily forming a low canopy below taller seasonal interest plants that easily grow among the brilliant green foil of the deciduous Fragile Ferns. When choosing a good groundcover companion to larger plants in the garden we look for plants that don’t prevent the larger structural and seasonal interest plants from thriving. Fragile ferns check all the boxes. This is a genus of temperate zone ferns with a worldwide distribution. There are 20 species currently known with 9 native to North America. Cystopteris are often called bladder ferns because their spore bearing structures (sori) are covered with an inflated bladder-like tissue (indusium). The name Cystopteris is derived from the ancient Greek ‘kustis’ or ‘cystis’ meaning bladder and ‘pteris’ meaning fern. Unfortunately for these amazing plants, bladder isn’t a great marketing name and few people have incorporated these incredible plants into their planting designs.

Our Top Cystopteris Picks

Cystopteris bulbifera (Bulblet Bladder Fern) Bublet Bladder Fern has a wide range from Canada south to Alabama. It is always found in association with high pH substrates and alkaline rocks such as limestone. In the Carolinas it is similarly restricted to the few limestone outcrops in the mountains, where it is highly localized and rare. It is much more abundant west of the Blue Ridge. This remarkable fern forms “bulblets” along the long, narrow, lacy fronds that can reach 2’ in length when happy. These “bulblets” fall off to form new plants. The clumps also spread slowly from short creeping rhizomes. The stems on this species are often tinged with red. (Hardiness Zone 3a-8b)

Cystopteris fragilis (Northern Fragile Fern) This beautiful little fern is essentially the northern version of the Southern Fragile Fern though it has a penchant for growing in more rocky areas and less frequently on the forest floor. This is a particularly beautiful plant to grow if you live in a colder zone and have a shaded rockery. The fronds are quite short, and it will form an 8” tall clump that is tighter in growth form than Southern Fragile Fern and of less utility as a green mulch. This species is very difficult in the Southeast outside of the mountain regions. (Hardiness Zone 3a-7a)

Cystopteris tennesseensis (Tennessee Bladder Fern) Tennessee Bladder Fern is a naturally occurring tetraploid hybrid fern that originated as a cross of Cystopteris protrusa and C. bulbifera. Cystopteris tennesseensis is a small deciduous fern that can be found on limestone cracks and cliff ledges from Wisconsin south to Georgia. In the Carolinas it is restricted to limestone at the Tennessee border and to highly localized populations on limestone “marl” outcrops in the coastal plain. The arching leaves are a vibrant green, arching and generally 8 – 18” long. In the garden it appreciates rich, circumneutral soil and good drainage and is a good candidate for the shaded rockery. (Hardiness Zone 4a-8b)

Cystopteris protrusa (Southern Fragile Fern, Lowland Bladder Fern) Cystopteris protrusa is by far the most useful member of the genus as a living mulch for shade gardens in the Southeast. The vibrant spring green coloration brightens up the forest floor and can be used to great effect in creating vibrancy in otherwise dark spaces. The plants produce a flush of leaves in early spring that tend to fade in mid-summer only to be replaced by another flush in the autumn that lasts until very cold weather sets in for the winter. This is another native that has a wide range from Minnesota south to Florida where it forms large deciduous patches in moist woodland ravines. In 5 years, Cystopteris protrusa forms an 8” tall x 5’ wide patch. (Hardiness Zone 4a-8b)

Bladder Fern Companion Plants

Try combining this fern with other delicate shade growers such as phlox, heuchera, anemonella and miniature hostas. In the wild, Cystopteris is often found growing with aquilegia, mahonia, and verbascum, making these also great companions for cystopteris in your garden. Try growing bladder fern in the crevices of a loose stacked stone wall. It will look fantastic and feel right at home. When you are ready to buy cystopteris for your garden, check out our online list of cystopteris for sale.