Asplenium adiantumnigrum Black spleenwort

Asplenium cuneifolium x A. onopteris.

Epithet is derived from adiantos, unwetted, and nigrum,black. Evergreen, 6 to 12 in. (15 to 30 cm).Zones 6 to 8.

description: The rhizome is erect to short-creeping. Brittle, round stipes are one-half the length of the frond and are a lustrous chestnut with black scales surrounding a slightly swollen base. The characteristic darkness transforms to green at or near the junction with the blade. Strongly triangular, lacquered green blades are a variable bipinnate to tripinnate with 5 to 12 pairs of pointed pinnae. Blades can be ascending or horizontal depending on exposure and the size of the frond. Sori are linear with a linear indusial flap.

range and habitat: The range for this species is erratic. It can be found in lower elevations in Scandinavia, where it is endangered because of overcollecting, rocky coastal or mortared wall sites in the British Isles, humid terrains in Central Europe, and North Africa, Kenya, and Iran. In addition, it frequents forested areas in the Himalayas, where it occurs in sites up to 9000 ft. (2700 m). Finally it is found in some very rare stations in the continental United States as well as lava and scrublands in Hawaii. Although primarily mildly basic, the substrates vary and include serpentine for subsp. cornunense. Chris Page (1982) warns that in Britain adders enjoy a mutual habitat.

culture and comments: In spite of its divergent distribution, this is not an easy plant to cultivate. Good drainage is essential. It will establish more readily in the fissures of a shaded rock wall than in the luxury of a garden bed. The whole plant is glowing and worth the experimentation to find it a happy home. And, in addition to being welcome in the garden, for those lucky enough to have an adequate supply the petite fronds serve admirably as a shiny foil in flower arrangements. There is considerable latitude in frond division and height with some 20 varieties ranging from incised to crested being described in the literature of the early 1900s. Many of these have been lost to cultivation, but I am nurturing and testing a congested 4-in. (10-cm) variety that came from spores gathered from a mortared wall in Britain. It is but one of the variables.

Asplenium adulterinum description: The rhizome is erect, bearing full rosettes of

Asplenium trichomanes x A. viride. lax fronds. The stipes are dark reflecting the Asplenium tri-

Epithet means "not pure." chomanes heritage but become A. viride green in the upper

Evergreen, 4 to 6 in. (10 to 15 cm). Zones 5 to 8. portions of the rachis, making it an easy task to identify this

Asplenium adiantum-nigrum in its preferred mural habitat in England.

The congested form of Asplenium adiantum-nigrum prefers a Asplenium adulterinum in container culture.

rocky limestone setting.

Rachis of Asplenium adulterinum progresses from black to green.

Asplenium Xalternifolium in a customized rocky habitat in the Jessen garden.

hybrid. Lanceolate, once-pinnate blades taper at both ends with 20 to 30 pairs of rounded pinnae. The sori are linear and covered with matching linear indusia. In spite of its hybrid origin, this fern reproduces readily from spores.

range and habitat: Asplenium adulterinum is rare in nature and grows in limestone crevices or, unlike its parents, on serpentine rocks in scattered sites in Scandinavia and Central Europe, where it is endangered. A very disjunct population occurs in British Columbia, Canada.

culture and comments: A charming dwarf, this hybrid adapts to rock garden culture (in pots or gardens) in a granular, well-draining, loose soil mixture. Specialized serpentine or limestone soil is, fortunately, not necessary for success. This fern prefers bright light with all but midday sun being acceptable.

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