Blechnum

Scientific name

Blechnum L.

Common names

swamp fern, marsh fern, toothed midsorus fern

Family

Blechnaceae

Similar genera

Acrostichum, Bolbitis, Crepidomanes

Native distribution

Blechnum indicum is native to Southeast Asia extending south to Australia.

B. serrulatum is native to Florida (United States), Central and South America.

Species cultivated

Blechnum indicum Burm.f.

B. serrulatum Rich.

Adventive distribution

none

Weed status

not weedy

Habit

amphibious, rhizomatousrhizomatous:
(adj) possessing rhizomes
fern

Brief description

Rhizomes horizontal to apically erect, stout, branched, densely scaly. Fronds erect to arching; stipestipe:
(n) stalk supporting leaf or leaf-like organ
stramineous and glabrousglabrous:
(adj) without hairs or scales
above, base dark with scales, lanceolatelanceolate:
(adj) lance-shaped; widest point below the middle, tapering to the apex
, acuminateacuminate:
(adj) tapering gradually to a point and forming more or less concave sides
, reddish-brown. Leaf bladeblade:
(n) (syn. lamina) the flat, expanded part of a leaf, frond, or petal (excluding, e.g., the petiole)
compound (imparipinnate); apexapex:
(n) the point farthest from the point of attachment; the tip (often pointed)
acuteacute:
(adj) tapering to a sharp, pointed apex with more or less straight sides; broader than acuminate; forming an angle of less than 90 degrees
; base truncatetruncate:
(adj) terminating abruptly, as if cut straight across
. PinnaePinna:
(n) one of the primary divisions or leaflets in a compound leaf or frond
sessile to shortly stalked; ± oppositeopposite:
(adj) (of leaves) two leaves per node; in pairs on opposite sides of an axis
; linear; apexapex:
(n) the point farthest from the point of attachment; the tip (often pointed)
tapering, acuteacute:
(adj) tapering to a sharp, pointed apex with more or less straight sides; broader than acuminate; forming an angle of less than 90 degrees
to acuminateacuminate:
(adj) tapering gradually to a point and forming more or less concave sides
; base truncatetruncate:
(adj) terminating abruptly, as if cut straight across
to cordatecordate:
(adj) heart-shaped; in the form of two rounded lobes
; marginmargin:
(n) edge; rim
serrulate; venationvenation:
(n) the arrangement of veins in a leaf
appearing pinnatepinnate:
(adj) in the form of a feather; of, e.g., leaflets, lobes, or veins: arranged in two rows along an axis
, closely spaced, fine; costaecosta:
(n) midvein of leaf or pinna or rachis of pinnately compound leaf
with small scales, triangular or irregularly shaped, almost transparent.

Natural habitat

swamps, marshes, wet prairies, areas subject to periodic inundation

Additional comments

A genus of nearly 150 species; here we focus on the amphibiousamphibious:
(adj) of a plant able to live on land or in water
species Blechnum indicum and B. serrulatum. There is some disagreement as to whether or not B. indicum and B. serrulatum are separate species, as they can be difficult to distinguish due to very similar morphological characteristics, which could be regarded as variation within a single species (Rolleri et al, 2010).

Blechnum serrulatum has broader, more oblongoblong:
(adj) two to four times longer than wide, with +/- parallel sides
pinnae that do not taper evenly; the costal scales are slightly larger and paler than those of B. indicum, which are very small and reddish brown; the venationvenation:
(n) the arrangement of veins in a leaf
of B. serrulatum is abaxially indistinct, while the venationvenation:
(n) the arrangement of veins in a leaf
of B. indicum is distinct on both surfaces (Chambers and Farrant, 2001). Additionally, recent molecular phylogenetic studies may lead to the taxonomic revision of Blechnum in the near future (Perrie et al, 2014).