Ferns and “Fern Allies”

By: Tracy Calla and George Rogers

Ferns and non-ferns having a similar life history (Fern Allies) belong to numerous families. These are in a state of taxonomic flux. Sorting them out is beyond the scope of the present effort, so for convenience all of the ferns and “Fern Allies” are lumped into the present section. There exist some 12,000 species of ferns. They and “Fern Allies” have no flowers, no fruits, and no seeds. Sexual reproduction is by spores. The gametophytes are tiny and free-living. Fern leaves are usually “fronds,” that is, large and pinnately compound or multiple times compound. The leaves of the Fern Allies are for the most part tiny (fraction of an inch long, with the exception of long quills in Isoetes) having a single vein. In most ferns the sporangia (spore cases) are in clusters called sori (singular sorus) on the undersides of the leaves. The Fern Allies in South Florida horticulture are mostly hanging-basket species of Lycopodium (Club-Mosses) and Selaginella (Spikemosses), or infrequent potted specimens of Equisetum (Horse-Tails, Scouring-Rushes), and Quillworts (Isoetes) in aquaria. Not being used appreciably in landscaping, these are set aside for present purposes.

Key to Ferns Prominent in South Florida Landscaping

(Many additional species are present as natives and as container plants)

1. Ferns tree-sized…Australian Treefern  (Cyathea cooperi)

1. Ferns herbaceous…2

2. Ferns having deeply lobed simple leaves with the round sori sunken on the undersides and raised on the upper sides, resembling warts…Wartfern (Phymatosorus scolopendria)

2. Fronds otherwise…3

3. Fronds simple, strap-shaped with pointed tips…Birdsnest Fern (Asplenium nidus)

3. Fronds compound or simple and forked…4

4. Ferns with conspicuously fuzzy “rabbit’s-foot” rhizomes…Rabbit’s Foot Fern (Davallia fijeensis)

4. Ferns otherwise…5

5. Ferns epiphytic, the simple blades forked at the tips...Staghorn Fern (Platycerium sp.)

(Fishtail Fern is a terrestrial fern with forked leaflets.)

5. Ferns otherwise, with compound fronds…6

6. Fronds doubly compound or once compound, the leaflets deeply lobed (almost twice compound)…7

6. Fronds once-compound, the leaflets not deeply lobed…9

7. Ferns with conspicuous fuzzy rhizomes; fronds triangular and lacey, the ultimate divisions < 1/3” wide…Rabbitsfoot Fern (Davallia fijeensis)

7. Ferns without conspicuous fuzzy rhizomes; fronds rounded to triangular, the ultimate divisions > 1/3” wide…8

8. Sori marginal, the fronds more or less palmate,  the ultimate divisions more or less wedge shaped…Maidenhair Ferns (Adiantum species)

8. Sori not at the edge of the leaflet, the fronds more or less triangular, the ultimate divisions pinnately lobed, making the leaf almost 3X compound…Mahogany Fern (Rumhora adiantiformis)

9. Leaflets ovate-lanceolate, bent, narrowly and long-tapered to a long-pointed tip…Holly Fern (Cyrtomium falcatum)

9. Leaflets otherwise…10

10. Leaflets ovate-lanceolate or rhombic, lopsided, blunt-tipped; young foliage red…Mahogany Fern (Didymochlaena truncatula)

10. Leaflets linear to narrowly lanceolate, abruptly tapered to the tips, straight…Nephrolepis (See separate key below)

Key to Nephrolepis Species Cultivated in South Florida

1. Leaflets forked like fish tail…Fishtail Fern (N. falcata forma furcans)

1. Leaflets otherwise…2

2. Plants with tubers; leaflet veins one-forked; leaflets rounded; sori bean-shaped; rachis with bicolored scales on top surface …Sword Fern (N. cordifolia)

2. Plants without tubers; leaflet veins twice forked; leaflets usually pointy; sori variable; rachis with no scales or with single-colored scales on top, or scales bicolored…3

3. Rachis woolly with bicolor scales dark at the center and light-colored around the edges (especially near the stipe base)…Asian Sword Fern (N. multiflora)

3. Rachis glabrous or at least not heavily covered with scales, and the scales present are the scales just one color…4

4. Leaflets sometimes over 1” wide and widely separated, without a basal lobe (or this very small), leathery, on short stalks…N. biserrata (Macho Fern)

4.  Leaflets narrower and overlapping, with a basal lobe, herbaceous, sessile…N. exaltata (Boston Fern)