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Boston fern, narrow swordfern, sword fern, tuber ladder fern, tuber sword fern, tuberous sword fern

Boston swordfern, sword fern, wild Boston fern

Stem

scales spreading, concolored.

scales spreading, concolored.

Leaves

2.5–10.7 × 0.3–0.7 dm.

4–15 × 0.5–1.2 dm.

Petiole

0.3–2 dm, moderately to densely scaly;

scales spreading, pale brown throughout.

0.2–4 dm, sparsely to moderately scaly;

scales spreading, pale brown to reddish brown, concolored.

Blade

lacking scales, glabrous (rarely with a few branched hairs abaxially).

glabrous, sparsely to moderately scaly abaxially near costae and adaxially.

Indusia

reniform to lunate or deltate-rounded, attached along broad sinus, 1.1–1.7 mm wide.

reniform to horseshoe-shaped, attached at narrow or broad sinus, 1–1.7 mm wide.

Tubers

present or absent.

absent.

Rachis

2.2–9 dm, points of pinna attachment 5–12 mm apart;

scales moderately spaced to dense, pale to dark brown, point of attachment distinctly darker.

2.4–16.3 dm, points of pinna attachment 7.3–21 mm apart;

scales moderately spaced, pale to dark brown, essentially concolored or margin indistinctly paler;

hairs absent.

Central

pinnae oblong to lanceolate-oblong, straight to slightly falcate, 0.9–5 × 0.4–0.9 cm, base auriculate-cordate, acroscopically overlapping rachis, acroscopic lobe deltate, margins entire to serrulate to smoothly crenate, apex acute to bluntly rounded;

costae adaxially glabrous.

pinnae deltate-oblong, slightly to distinctly falcate, 2.3–7.4 × 0.6–1.8 cm, base truncate to truncate-auriculate or auriculate, occasionally overlapping rachis, acroscopic lobe deltate to acute, margins serrulate, apex acute to deltate;

costae adaxially glabrous.

2n

= 82.

Nephrolepis cordifolia

Nephrolepis exaltata

Habitat Terrestrial or epiphytic in wet, shady places, limestone ledges, cliffs, rock, roadsides, and often old homesites or waste places, widely escaped from cultivation and only questionably native to any particular region Terrestrial or epiphytic in forested to open habitats, most often as an epiphyte
Elevation 0 m [0 ft] 0 m [0 ft]
Distribution
from FNA
FL; HI; Mexico; Central America; South America; West Indies; Africa; se Asia
[WildflowerSearch map]
[BONAP county map]
from FNA
FL; West Indies; Pacific Islands in scattered locations
[WildflowerSearch map]
[BONAP county map]
Discussion

Nephrolepis exaltata is occasionally found farther north in the flora, but only as an escape from cultivation. Nephrolepis exaltata is usually confused with N. cordifolia when sterile; the latter species can be distinguished by its distinctly bicolored, adaxial rachis scales. These bicolored scales will distinguish N. cordifolia from all of the other species, even in the absence of other key features.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 2. FNA vol. 2.
Parent taxa Dryopteridaceae > Nephrolepis Dryopteridaceae > Nephrolepis
Sibling taxa
N. biserrata, N. exaltata, N. multiflora, N. ×averyi
N. biserrata, N. cordifolia, N. multiflora, N. ×averyi
Synonyms Polypodium cordifolium, Aspidium cordifolium Polypodium exaltatum
Name authority (Linnaeus) C. Presl: Tent. Pterid. 79. (1836) (Linnaeus) Schott: Gen. Fil. plate 3. (1834)
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