Davallia is a genus of ferns in the family Davalliaceae, order Polypodiales, class Polypodiopsida. Commonly known as hare's foot ferns, rabbit foot ferns, deersfoot ferns, and ball ferns, the genus comprises approximately 40–65 species distributed across tropical and subtropical regions of Asia, the Pacific, Australia, and Africa.
The plants are characteristically epiphytic or epipetric, growing on the surfaces of trees or rock faces rather than in soil. Their most distinctive feature is the long, creeping aerial rhizome, which is covered in dense, often pale or russet-coloured scales and extends well beyond the pot or support on which the plant grows — the source of the popular “foot” common names. Fronds arise from these rhizomes on stipes that are articulate at the base, meaning they break cleanly from the rhizome when dead, leaving behind a persistent cushion-like base (phyllopodium). Veins are free, the annulus of the sporangia is vertical, spores are monolete, and the sporangium stalk is three-rowed.
Davalliaceae is phylogenetically sister to Polypodiaceae, the largest family of ferns, and shares certain morphological traits with it. The family's circumscription has changed substantially: a 2008 molecular phylogenetic study demonstrated that none of the then-recognised polyspecific genera were monophyletic, leading to a revision into five genera. The Pteridophyte Phylogeny Group classification of 2016 (PPG I) subsequently reduced the family to a single genus, Davallia, sinking Araiostegiella and other segregates into synonymy. The genus is now divided into seven sections. Gymnogrammitis and Leucostegia, once included in Davalliaceae, have been re-placed in Polypodiaceae and Hypodematiaceae respectively.
Well-known members include Davallia canariensis (Canary Islands and the Iberian Peninsula), Davallia fejeensis (Fiji), Davallia denticulata (Old World tropics), and Davallia mariesii (tropical Asia), the last widely grown as a houseplant.
Etymology
The genus name Davallia honours Edmund Davall (1763–1798), a Swiss botanist who corresponded extensively with James Edward Smith, founder of the Linnean Society.
Distribution
Davallia species are native to tropical and subtropical regions spanning Asia, the Pacific Islands, Australia, and Africa. Plants grow most commonly as epiphytes on tree bark or as lithophytes in rock crevices, occasionally as terrestrials; they are especially diverse in Southeast Asia and Malesia.
Ecology
Davallia ferns occupy epiphytic and epipetric niches in humid tropical and subtropical forests. Their long, scale-covered rhizomes allow the plants to spread across bark surfaces and through rock crevices without rooting in soil, absorbing moisture and nutrients from rain, organic debris, and humid air. This growth habit makes them tolerant of periodic dry spells once established.
Cultivation
Davallia species are popular houseplants and ornamental ferns valued for their ornamental creeping rhizomes and finely divided fronds. They thrive in bright indirect light, well-drained epiphytic or bark-based media, and moderate humidity. Plants are often grown in hanging baskets or mounted on bark, allowing the rhizomes to trail freely. Watering should be thorough but infrequent enough to let the medium partially dry; the rhizomes are sensitive to prolonged waterlogging. Several species, notably Davallia fejeensis and Davallia mariesii, are widely grown as houseplants across temperate regions.
Taxonomy Notes
Davallia is the sole accepted genus in the family Davalliaceae (PPG I, 2016). Molecular phylogenetic work in 2008 demonstrated that the previously recognised polyspecific genera were not monophyletic, prompting a revision of the family into five genera before PPG I consolidated all into Davallia with seven internal sections. Gymnogrammitis and Leucostegia, historically placed in Davalliaceae, now belong in Polypodiaceae and Hypodematiaceae respectively. Species estimates have ranged from 63 (2008 treatment) to about 65 (PPG I), with ongoing description of new species such as Davallia napoensis (2011).
