Cystopteris alpina (alpine), synonym C. regia, is small and delicately beautiful with lacy tripinnate, slightly oval, deciduous fronds, and narrow pinnules. The stipes are up to one-half of the length of the frond, which is variable in size, though usually under 12 in. (30 cm) in height. It is similar in outline to C. fragilis but distinguished by an oval blade and finely divided, toothed pinnules. Should you be reading this in Lapland, here is a plant for your garden. The species not only wants, but also excels in alpine habitats "blessed" with nature's thermal blanket of long, snow-covered winters. "Belongs in snowbeds where no other ferns grow, often associated with
Salix polaris"(0llgaard and Tind 1993). It is found exclusively on limestone from northern Scandinavia to the Pyrenees. In cultivation, it is for Zones 2 and up to perhaps 7 or 8, but must be planted in an alkaline cobble or equivalent, where summers are reliably cool.
Cystopteris diaphana (transparent), synonym C. fragilis subsp. diaphana, is a deciduous native of Mexico, South America, and southern Europe. The small, usually under 1-ft. (30-cm), fronds are tripinnate with pointed tips and pinnules that sometimes overlap. In nature it grows among rocks and in ravines primarily in humid sites. German and British enthusiasts are cultivating it successfully in Zones 6 to 9.
Cystopteris dickeana (after Dr. George Dickie), Dickie's bladder fern, synonym C. fragilis var. dickeana, is rare in nature with the original find of the early 1800s, and perhaps the only true type, growing on dripping rocks in a coastal cave near Aberdeen, Scotland. Although its botanical status is insecure and under continued taxonomic scrutiny, it is also reported from assorted locales in Europe and, probably, the United States (opinions vary). Many botanists separate it from the spiny spored C. fragilis because of its wrinkled, warty spores (which we are not likely to notice in the garden). Horticulturally, the deciduous pinnae are set close together, frequently overlapping, with matching close-set pinnules. Note that the sori edge the pinnules. This species comes true from spores and is an attractive, 4- to 8-in. (10- to 20-cm) treasure for troughs and rubble-enriched rock gardens in Zones 3 to 8.
Cystopteris laurentiana (from the Saint Lawrence River area) is an upright, deciduous species with bipinnate, lanceolate fronds to 18 in. (45 cm). Bulblets are rare but when present are small with distorted shapes. The plant is best suited to moist limestone cliffs in cold-challenged northern areas of North America and Europe. As a fertile hybrid derived from some chromosome acrobatics between C. bulbifera and C. fragilis, it is difficult to distinguish from the latter. Flora of North America (1993) recommends looking for the occasional bulblets and unique glandular hairs that give the species a separate status from either parent.
Cystopteris montana (from mountains), mountain bladder fern, is a handsome, arctic-inclined elusive fern in nature (and even more so in cultivation). Years ago, my family was directed to a Colorado site where, it was promised, we would be immersed in masses of the desired fern. On arrival, I offered a bribe to my children; the first to find a fertile frond would be rewarded with $1.00 (money went farther in those days). After about 15 minutes, the stakes increased to $5.00 for the "first to find a fern." It was not to be. (I suspect we were too late in the season and that during a spring visit we would have seen the envisioned delight.) It is similar in outline to the more familiar gymnocarpiums with broad 18-in. (45-cm), triangular, deciduous fronds held horizontally or slanting downwards from pale green stipes. The long innermost pinnules on the lowest pinnae are significant and separate it from C. sudetica, which has correspondingly short interior pinnules. Though rarely cultivated, it is an attractive collector's choice for wet basic soil and cool to cold (even better) winter sites. It is recommended for Zones 2 to 5 but is known in cultivation for up to cool Zone 8 gardens. Wherever grown, it must have shade and a guaranteed rest in winter. Fern trivia buffs, and we are many, should note that when bruised the fronds are reputed to smell like prussic acid, which all references compare to the fragrance of almonds in assorted stages of abuse.
Cystopteris moupinensis (from Mupin, China) is a small, deciduous charmer native to China and extending beyond into Asia. The stipes grow from creeping rhizomes and are over one-half of the 4- to maybe 6-in. (10- to 15-cm) long fronds. The delicate blades are bipinnate to tripinnate and triangular. This species is likely to be lost to view in the garden, but should elicit admiring oohs and aahs along with envious, "Who's that?" questions in shade-protected troughs and strategically located containers in Zones 5 to 8.
Cystopteris reevesiana (after U.S. botanist Timothy Reeves), southwestern brittle fern, synonym C. fragilis var. tenuifolia, grows on rocks and terrestrially in assorted substrates from Utah and Colorado south to Texas and Mexico. The rhizomes are creeping, producing long basally dark stipes and finely divided bipinnate to tripinnate blades. The pinnae are widely spaced giving the entire frond a feathery touch. It is easy and cold hardy in Zones 5 to 9.
Cystopteris sudetica (from the Sudetenland of the Czech Republic and Poland) is a rare species from Europe, Japan, China, Korea, and Siberia, so yes, cold hardy. The rhizome is long-creeping and the stipes are tall, usually better than one-half of the 18 in. (45 cm) frond length. The tripinnate blades are broadly ovate-triangular and lightly scaly. Cystopteris sudetica is visually similar to C. montana but is more robust and lacks the latter's elongate innermost lowest pinnule (ba-siscopic) on the basal pinnae. Like C. montana its habitat of choice is in humus on "limestone debris." It is cultivated in Europe and when available in North America should be incorporated into moist limestone, rocky crevices in shady sites from Zones 3 to 8.
Cystopteris tennesseensis (of Tennessee), Tennessee bladder fern, is the deciduous, fertile hybrid between C. bulbifera and C. protrusa. At a mature height of 18 in. (45 cm), it is smaller in all proportions, but otherwise similar in portraiture to C. bulbifera, including a complement of miniature ready-to-roll bulblets. It is locally common in the Ozarks where it occupies limestone shelves and moist crevices. Grow it in lime-enriched, semishaded cobbles in Zones 5 to 8. Long fronds are fresh light green furnishings and more narrowly triangular than the comparable foliage of either parent.
Cystopteris tenuis (slender), slender fragile fern, MacKay's brittle fern, synonym C. fragilis var. mackayi, is a candidate for determining successful or discouraging results on that last final exam in Botany 501 (note this is an advanced course) with an A awarded to the student who can define the differences between it and closely related fellow cystopteris. It differs from C. protrusa and C. fragilis in having pinnae that curve upwards and in having rounded margins as opposed to serrate. The 18-in. (45-cm) deciduous fronds are bipinnate on green to hay-colored stipes of just under one-half of the frond length. The species grows on rocks as well as soil and is espe cially abundant in the Great Lakes area of North America with an eastward spread and a few disjunct westward populations. It is easily cultivated, without a strong soil preference, and can be used with other cystopteris in a comparative educational exhibit for the cognoscenti in Zones 4 to 8.
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