Blechnum nudum

Fishbone water fern, black-stemmed water fern Epithet means "naked."

Evergreen, 2 to 4 ft. (60 to 120 cm). Zones 8 (with protection) and 9. Dimorphic.

description: The thick rhizome is erect, occasionally developing a trunk. Glossy black stipes with a slight groove and shiny basal scales are one-fourth of the frond length. Lanceolate, 2- to 3-ft. (60- to 90-cm), once-pinnate, sterile blades taper symmetrically from top to bottom. The erect fertile fronds are shorter than the sterile with linear spore-bearing pinnae.

range and habitat: This Australian endemic romps at will in acid soil in moisture-laden streamside or lowland sites as well as on forested slopes. With adequate moisture it is also sun tolerant, albeit with a corresponding loss of height and color saturation.

Green foliage on Blechnum nudum in the Gassner garden.

Blechnum novae-zelandiae in the Kohout garden.

Green foliage on Blechnum nudum in the Gassner garden.

culture and comments: A common fern in its home country, this is a handsome upright shuttlecock for light shade and rich dampish soil. It is successfully cultivated in the Seattle area, although the trunk needs winter cosseting. I like it in a container, which, should an arctic emergency threaten, can be moved to a temporary shelter. Spores of this species need to be sown as soon as ripe, but will then reward the propagator with prompt and vigorous growth.

Blechnum occidentale Hammock fern Epithet means "western."

Evergreen, 1 to 2 ft. (30 to 60 cm). Zones 9 to 11, or greenhouse.

description: The rhizome is erect with an extensive network of stolons that produce dense stands of cascading, striking ruddy and glossy green foliage. The 6- to 10-in. (15- to 25-cm) stipes are scaly at the base and half of the frond length. Monomorphic, broadly lanceolate, once-pinnate blades taper to narrow points at the apices. Sori are linear on the midribs of the fertile pinnae.

range and habitat: This common fern is an unforgettable sight along roadsides in the West Indies, Mexico, and South America. It grows in the coarse duff of forest floors in shaded tropical woodlands.

culture and comments: Unlike the similar Blechnum appendiculatum, this species is glabrous along the rachis. It is a member of a complex group of Mexican blechnums all of which are receiving botanical scrutiny as of this writing. By whatever classification, it is a noteworthy addition to and showy attraction in frost-free, humid sites (as well as in flower arrangements). Light shade and moist to wet acid soil keep it at its optimum party-dressed best.

Blechnum penna-marina Alpine water fern, little hard fern

Epithet means "sea feather" or "sea pen."

Evergreen, 4 to 8 in. (10 to 20 cm).Zones 6 to 8. Dimorphic.

description: The rhizome is creeping, producing tight clusters of prostrate sterile fronds and upright spikes holding minute fertile pinnae. The stipes of one-fourth to one-third of the sterile frond length are grooved with small tufts of basal scales. The linear, once-pinnate, 1/2-in. (13 mm) wide sterile blades emerge in brilliant russet tones with 20 to 25 pairs of thick, sessile pinnae arranged in a zigzag fashion. Fertile fronds are vertical and taller with stipes of up to one-half of their length and tight inrolled hard knobs of fleshy pinnae with a firm grip on the sori. Spores are released in late summer to early autumn.

range and habitat: Blechnum penna-marina is as varied in its native habitats as it is accommodating in cultivation. its range extends from wet lowlands to alpine talus in New Zealand and Australia with related colonies in South America. The South American material is generally larger in all of its proportions than the magnificent compact buns sometimes designated as var. alpinum from exposed upper montane habitats of New Zealand. Those from comparable areas in Chile are upright clusters of dwarf spikes. in addition to the traditional Southern Hemisphere sites for these common colonizers, there are unexpected (and inexplicable), extraordinarily disjunct populations in the Mexican highlands of Chihuahua and Durango (Mickel and Smith 2004).

culture and comments: This is a marvelous fern for ground covering with its small stature and adaptability. in the Pacific Northwest it is an excellent choice for sunny sites where it remains tidily compact and colorful throughout the seasons. In hot climates it needs protection from intense midday sunshine. By contrast, too much shade encourages it to become raggedy and a tad too rambunctious. A dwarf selection maturing at 5 in. (13 cm) in sunshine is especially attractive and popular for lining mixed container plantings. All prefer acidic, well-drained moist soils but are forgiving when watering requirements are treated casually. Like many creeping ferns, and blechnums in particular, it does not propagate readily from spores. (South American material is more responsive than that from New Zealand.) However, with its crawling rhizomes,

Lush tropical fronds on Blechnum occidentale in the warmth and humidity of Trinidad.

Blechnum penna-marina in an alpine scree in New Zealand.

Lush tropical fronds on Blechnum occidentale in the warmth and humidity of Trinidad.

Blechnum penna-marina in an alpine scree in New Zealand.

Blechnum penna-marina in the higher elevations of the Conguillio National Park in Chile. Photo by Richie Steffen, Miller Botanical Garden.

Forked tips of Blechnum penna-marina 'Cristatum'.

Forked tips of Blechnum penna-marina 'Cristatum'.

Another view of Blechnum penna-marina in the higher elevations of the Conguillio National Park in Chile. Photo by Richie Steffen, Miller Botanical Garden.

division is easy. All it takes is a sharp shovel and a handy pot of fresh soil.

'Cristatum' (crested) is a crested variety with split frond tips.

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