Identifying Southwest Florida's Ferns

Pinnate Frond

To identify a fern with a pinnate frond, begin with the first question and continue until you get a "yes" answer. If more questions follow, use the same procedure. Fern speak: pinna (plural: pinnae) is the green, leaf-like part of the frond

1. Are the fronds really large -- 6 feet and more -- with wide, thick, smooth pinnae (the terminal pinna is about the same size as the nearest ones)? YES, or 1. Is the single terminal (tip) pinna shorter than the other pinnae? YES, or 1. Is the single terminal (tip) pinna noticeably longer than the other pinnae? YES, or 1. Is the terminal (tip) pinna divided into three distinguishable lobes (deltate)? YES There are no more pinnate frond questions in this section. If it is a pinnate frond, the answer to one of the above four questions will be a "yes."

Pinnate Fronds, single terminal (tip) pinna is shorter than the other pinnae... 2. Are the tips of the pinnules mostly pointed? YES, or 2. Are most of the pinnae forked at the tip, giving a fishtail-like appearance? YES, or 2. Are the tips of the pinnules blunt and rounded, and do the pinnae strongly overlap? YES There are no more pinnate frond questions in this section. If it is a pinnate frond whose terminal pinna are shorter than the other pinnae, the answer to one of the above three questions will be a "yes."

Pinnate Fronds, terminal pinna shorter than other pinnae, pinnules mostly pointed... 2. Are the pinnae separated enough so you can easily see space between them, and are the mature fronds around 4 to 8' long? YES, or 2. Are the pinnae very close, seeming to overlap, and the midrib divides each into two almost equal parts? YES There are no more pinnate frond questions in this section. If it is a pinnate frond whose terminal pinna is shorter than the other pinnae and the tips of the pinnules are pointed, the answer to one of the above two questions must be a "yes."

Pinnate Fronds, terminal pinna longer than neighboring pinnae... Note: sori are the small, brown roundish spore cases found along the underside of the frond 2. Is the terminal pinna noticeably longer than the immediate neighboring pinnae, and are the sori in a line along the midrib? YES, or 2. Is the terminal pinna slightly longer than the immediate neighboring pinnae, are the pinnae long and thin, and are the sori along the margin or edge? YES There are no more pinnate frond questions in this section. If it is a pinnate frond whose terminal pinna is longer than the other pinnae, the answer to one of the above two questions will be a "yes."

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Acrostichum danaeifolium

(Giant Leather Fern)

pinnate frond

Description	pinnae stiff, have leathery look; 20-30 pairs of pinnae lie close together along the stem, all with wavy edges and gradually decreasing in size to the tip; the pinnae are thick and tough-feeling
Rhizome	massive, creeping
Spores	sori on upper 1/2 to 1/3 of mature fronds; golden-brown to rust-brown and completely cover the underside of the pinnae; feel like suede or felt to the touch (photo above right)
Veins	netted
Growth	in fresh-water swamps; likes wet feet; prefers full sun for at least part of the day but will grow where shaded; grows in clumps arching to more or less erect in the middle of the clump
Similar	Acrostichum aureum (Leather Fern, Golden Leather Fern) grows in brackish water, salt marshes (not found at Corkscrew) slightly smaller venation angled at 45 degrees

Nephrolepis biserrata

(Giant Sword Fern, Sword Fern)

pinnate frond

Description	fronds frequently vine-like; narrows towards top but doesn't narrow significantly towards base; pinnae spaced apart along midrib and taper to point; pinnae are four times or more longer than wide; even serrations around edge of each pinna (tiny teeth alternate with larger teeth hence the name "biserrata"; 3-7' tall, 6-12" wide; pinnae margin wavy; base portions of mature stipes often with a few loose reddish-brown scales
Rhizome	ascending or erect; scaly, with long threadlike stolons producing young plants along its length
Spores	sori round to semicircular; occur evenly around entire edge of underside of each pinna (photo above right)
Veins	free
Growth	usually terrestrial but can be epiphytic; often in open places or areas or partial shade; fronds vine-like and clamber over shrubs and up tree trunks
Similar	Nephrolepis exaltata (Sword Fern, Boston Fern/native) pinnae slightly overlapping frond tapers at top and bottom Nephrolepis cordifolia (Sword Fern, Boston Fern/exotic. Tuberous Sword Fern) pinnae slightly overlapping frond tapers at top and bottom pinnae tips blunt and rounded Nephrolepis multiflora (Asian Sword Fern) dark brown scales on stipe bases erect hairs on pinna vidvein

Nephrolepis exaltata

(Boston Fern/native, Sword Fern, Wild Boston Fern)

pinnate frond

Description	fronds 1-7' long, 2.5-5" wide, and taper towards both the tip and the base; most of the pinnae are between two and three times as long as wide and lie next to eachother along the midrib of the frond; midrib of each pinna divides it about evenly for most of its length; base of each pinna is slightly widened (thumb)
Rhizome	ascending or erect; scaly, with long threadlike stolons producing young plants along its length
Spores	sori kidney-shaped or semicircular along margins of pinnae (photo above right)
Veins	free
Growth	sun or shade but develops best in open sunny spots where it is dense; found in any kind of hammock on fallen trees and in humus
Similar	Nephrolepis biserrata (Giant Sword Fern) space between pinnae frond tapers only at top and not significantly at bottom Nephrolepis cordifolia (Sword Fern, Wild Boston Fern/exotic. Tuberous Sword Fern) pinnae slightly overlapping frond tapers at top and bottom pinnae tips blunt and rounded Nephrolepis multiflora (Asian Sword Fern) dark brown scales on stipe bases erect hairs on pinna vidvein

Nephrolepis falcata (exotic)

(Fishtail Sword Fern)

pinnate frond

NOTE: a cultivar of Nephrolepis biserrata (Giant Sword Fern) that escaped cultivation, it was at one time labeled Nephrolepis biserrata cv. Furcans; it is not considered invasive

Description	the tips of the pinnae fork into two tips giving a "fishtail" appearance to each pinna; frond narrows towards top but doesn't narrow significantly towards base
Rhizome	ascending or erect; scaly, with long threadlike stolons producing young plants along its length
Spores	sori kidney-shaped or semicircular along margins of pinnae (photo above right)
Veins	free
Growth	sun or shade but develops best in open sunny spots where it is dense
Similar	none with forked pinna tips

Nephrolepis cordifolia (exotic)

(Boston Fern/exotic, Tuberous Sword Fern, Sword Fern)

pinnate frond

NOTE: Listed in the Florida Exotic Pest Council's "1995 List of Florida's Most Invasive Species" because it invades and disrupts native plant communities; frequently sold in nursery and garden shops as Boston fern, Hardy Fern, Large Fern, Erect Sword Fern

Description	mature fronds to 30" long; pinna tips blunt and rounded; noticeable "thumbs) at base of each pinna, 2.5-5" wide, and taper towards both the tip and the base; most of the pinnae are between two and three times as long as wide and lie next to eachother along the midrib of the frond; midrib of each pinna divides it about evenly for most of its length; base of each pinna is slightly widened (thumb)
Rhizome	ascending or erect; scaly, with long threadlike stolons (roots) which frequently bear small roundish tubers
Spores	sori semicircular occuring evenly around entire edge of underside of each pinna midvein
Veins	free
Growth	sunny but sometimes in partial shade; usually terrestrial but can be epiphytic, especially on palmettos
Similar	Nephrolepis biserrata (Giant Sword Fern) space between pinnae pinna tips somewhat pointed frond tapers only at top and not significantly at bottom Nephrolepis exaltata (Boston Fern/native, Sword Fern) pinnae slightly overlapping pinna tips somewhat pointed Nephrolepis multiflora (Asian Sword Fern) dark brown scales on stipe bases erect hairs on pinna vidvein

Blechnum serrulatum

(Swamp Fern)

pinnate frond

Description	terminal pinna segment longer than closest pinnae; fronds 2-6' tall, 4-6" wide; stipe 1/3 to 1/2 of frond length; pinnae with fine teeth along margin, narrowed at bases; dark green but stiff fronds in drier habitats a lighter shade of green; young fronds have a pinkish blush; blades don't taper at base of frond
Rhizome	long-creeping; fronds scattered along rhizome
Spores	linear in two rows close to the midrib of each pinna (photo above center)
Veins	free
Growth	grows lushly in moist high-light spots; where grows in drier sunny places, fronds rigid and somewhat stunted (photo above right)
Similar	Pteris vittata (Ladder-Brake Fern) pinnae thinner sori along margins instead of midvein terminal pinna segment about same size as closest pinnae Thylepteris serrata (Cypress Fern) sori completely cover underside of pinnae

Pteris vittata

(Ladder-Brake Fern, Chinese Brake Fern)

pinnate frond

Description	1-3' tall, stipe 1/6-1/3 the frond length; terminal pinnae ae sharply toothed; stipe and rachis densely clothed with hair-like scales; terminal pinna about same length as closest pinnae
Rhizome	stout, short-creeping
Spores	sori along margins on underside of pinnae (photo above right)
Veins	free, forking
Growth	likes higher untrient soils in pine woods and disturbed sites
Similar	Blechnum serrulatum (Swamp Fern) sori along pinna midvein instead of margin terminal pinna longer than closest pinnae Thylepteris serrata (Cypress Fern) sori completely cover underside of pinnae

Tectaria incisa

(Incised Halbred Fern)

pinnate frond

Description	large coarse fern with fronds to about 4-5 feet tall; pinnae clustered on stem and dull light green; terminal pinna deltate (broken into three's); lowermost pinnae deeply two-lobed (photo above left); pinnae margins mostly uncut but wavy
Rhizome	short-creeping
Spores	round in single rows on either side of lateral veins (photo above right)
Veins	netted
Growth	rocky hammocks
Similar	Tectaria heracleifolia (Broad Halbred Fern) pinnae shiny, dark green and deeply toothed rather than wavy fronds smaller, to only about 2'
Notes	only found in southern tip of Florida peninsula, almost exclusively in Broward, Dade, and Palm Beach Counties