Christella dentata
Common names
christella
Biostatus
Native
Category
Vascular
Structural class
Ferns
Flower colours
No flowers
Detailed description
Somewhat soft and delicate fern, producing numerous tufts of pinnate fronds from a stout, somewhat woody, creeping rhizome. Rhizome, usually semi-exposed, covered in the frond base remnants. Fronds not long-persistent, broadly ovate to oblong in outline, up to 2 m long (usually much less), pale green to yellow-green, soft, wilting easily when broken, all parts clad in soft velvety hairs. Primary pinnae with the exception of the basal prominently hastate pair, alternating along rhacis, oblong to lanceolate, 300–1000 × 130–400 mm, with longest pinnae located within the central portion of the frond, subsequent pairs decreasing in size toward either end of frond. Secondary pinnae prominently lobed, lobes, oblong, apex bluntly truncate. Sori are arranged in up to 7 pairs on the pinnae lobes. Sorus covered by a heart- to kidney-shaped indusia.
Similar taxa
Cyclosorus interruptus though similar is smaller, scarcely creeping, and has long persistent, hairless, leathery, deltoid fronds, which are less deeply divided. Pakau pennigera is also similar and has been found growing with christella. Christella differs from that species by its widely creeping habit, and softer, very hairy fronds with oblong rather than ovate secondary pinnae. In New Zealand Christella dentata comprises two races, the one described here, and a second race which is mostly confined to geothermally active areas (though it also occurs in Te Paki) in the North Island. This race, known as the “Geothermal Race”, also extends to the Kermadec Islands (Raoul Island), and possibly occurs elsewhere in the Pacific. The “Geothermal Race” differs from the form of C. dentata described above by having a shortly creeping rhizome, the plants producing overtime an erect, caudex (trunk) the base of which is typically covered in vegetative buds. The fronds often appear narrower than the typical form of C. dentata described above, and may be more densely covered in milky white hairs. The “Geothermal Race” is considered by many botanists to be a distinct, possibly unnamed species (see Taxonomic Notes below).
Distribution
Indigenous. New Zealand: Kermadec Islands (Raoul Island), North Island (known only from Kaitaia north, although somewhat similar plants have been found twice near Kawhia and Piopio (now extinct at both locations), and there are forms of unknown origin present in horticulture which have naturalised in Auckland, Hamilton and Wanganui). A pan tropical species ranging from Crete throughout the warmer parts of the world to New Zealand. Christella dentata is a widespread and variable old world species, showing a wide range of local variation. Many of these variants have been given formal names but acceptance of these is not universal. New Zealand plants appear to be the same form as that commonly found in eastern Australia and Norfolk Island.
Habitat
A short-lived fern of recently disturbed ground. In New Zealand proper the typical form of C. dentata is found naturally only in the far north in the warm, frost-free situations such as coastal wetlands, along river banks and in alluvial forest remnants. The same form is abundant on the Kermadec Islands (on Raoul Island only)
Current conservation status
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2022-2023 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website. This report includes replaces all previous NZTCS lists for vascular plants. Previous assessments can be found here.
- Conservation status of vascular plants in Aotearoa New Zealand, 2023. 2024. Peter J. de Lange, Jane Gosden, Shannel P. Courtney, Alexander J. Fergus, John W. Barkla, Sarah M. Beadel, Paul D. Champion, Rowan Hindmarsh-Walls, Troy Makan and Pascale Michel Department of Conservation. Source: NZTCS and licensed by DOC for reuse under the Creative Commons Attribution 4.0 International licence.
2023 | At Risk – Naturally Uncommon | Qualifiers: PD, SO
Threats
In New Zealand proper currently known from just one natural site, this is protected as a QE II covenant. At this site it is threatened by natural succession and the rank growth of weeds following fencing of the forest remnant in which it grows (de Lange et al. 2010). Current management at the QEII site involves handweeding plants, and population enhancement. Christella dentata is however abundant on Raoul Island (see also Distribution and Taxonomic Notes).
Detailed taxonomy
Family
Synonyms
Polypodium dentatum Forsskal, Dryopteris dentata (Forsskal) C.Chr., Thelypteris dentata (Forsskal) St John, Cyclosorus dentatus (Forsskal) Ching, Polypodium nymphale G.Forst.
Taxonomic notes
Two races of Christella exist in New Zealand. The first of these has a widely creeping, brittle, usually buried rhizome (and is the race discussed mostly by this fact sheet), the second has shortly creeping rhizomes, with well established plants developing a stout caudex over time, the bases of which are often covered in vegetative buds. The first race is naturally confined to a few sites near Kaitaia (Awanui) and on Raoul Island (where it is abundant). However, the same form is also naturalised in Auckland and Hamilton cities, and possibly also Whanganui. The second race, because in the North Island it is mostly associated with geothermally active sites is widely known as the “geothermal race”. However, the same race also occurs on Raoul Island (where it grows with the first race), and possibly also at Te Paki (and at one time near Kawhia and Piopio). Taxonomic resolution of these forms, in isolation, in New Zealand would be unwise, especially as C. dentata is widely distributed across much of the world and extremely variable within that range. Therefore pending a thorough revision of the species, as an interim measure it seems best to acknowledge that in New Zealand C. dentata is variable, and that two races exist but that further action on their status without a global context is possibly beyond our scope.
Endemic taxon
No
Endemic genus
No
Endemic family
No
Ecology
Flowering
Spores may be found throughout the year
Fruiting
Spores may be found throughout the year
Life cycle and dispersal
Seeds are dispersed by ballistic projection, wind and water (Thorsen et al., 2009).
Propagation technique
Very easily grown by the divisions of whole plants and from spores. In warm sheltered gardens this species frequently naturalises. It is frost sensitive. Although in New Zealand it is primarily a species of wetlands, in cultivation it can, and will grow in almost any soil and moisture regime.
Wetland plant indicator status rating
Information derived from the revised national wetland plant list prepared to assist councils in delineating and monitoring wetlands (Clarkson et al., 2021 Manaaki Whenua – Landcare Research Contract Report LC3975 for Hawke’s Bay Regional Council). The national plant list categorises plants by the extent to which they are found in wetlands and not ‘drylands’. The indicator status ratings are OBL (obligate wetland), FACW (facultative wetland), FAC (facultative), FACU (facultative upland), and UPL (obligate upland). If you have suggestions for the Wetland Indicator Status Rating, please contact: [Enable JavaScript to view protected content]
FAC: Facultative
Commonly occurs as either a hydrophyte or non-hydrophyte (non-wetlands).
Other information
Cultivation
Specimens of Northland origin are held by several botanic gardens, universities and private fern growers. Occasionally this species is offered for sale by commericial nurseries, though in these cases it is not always certain whether the plants on sale are of New Zealand origin.
Etymology
dentata: Toothed
NVS code
The National Vegetation Survey (NVS) Databank is a physical archive and electronic databank containing records of over 94,000 vegetation survey plots - including data from over 19,000 permanent plots. NVS maintains a standard set of species code abbreviations that correspond to standard scientific plant names from the Ngä Tipu o Aotearoa - New Zealand Plants database.
CHRDEN
Chromosome number
2n = 144
Previous conservation statuses
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2022-2023 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website. This report includes replaces all previous NZTCS lists for vascular plants. Previous assessments can be found here.
- Conservation status of vascular plants in Aotearoa New Zealand, 2023. 2024. Peter J. de Lange, Jane Gosden, Shannel P. Courtney, Alexander J. Fergus, John W. Barkla, Sarah M. Beadel, Paul D. Champion, Rowan Hindmarsh-Walls, Troy Makan and Pascale Michel Department of Conservation. Source: NZTCS and licensed by DOC for reuse under the Creative Commons Attribution 4.0 International licence.
2017 | At Risk – Naturally Uncommon | Qualifiers: PD, SO
2012 | At Risk – Naturally Uncommon | Qualifiers: PD, SO
2009 | Threatened – Nationally Critical | Qualifiers: CD, SO
2004 | Threatened – Nationally Critical
Referencing and citations
References and further reading
de Lange PJ, Heenan PB, Norton DA, Rolfe JR, Sawyer JWD. 2010. Threatened Plants of New Zealand. Canterbury University Press, Christchurch. 471 p.
Thorsen MJ, Dickinson KJM, Seddon PJ. 2009. Seed dispersal systems in the New Zealand flora. Perspectives in Plant Ecology, Evolution and Systematics 11: 285–309. https://doi.org/10.1016/j.ppees.2009.06.001.
Attribution
Fact sheet prepared for NZPCN by P.J. de Lange (12 October 2003). Description modified from de Lange et al. (2010).
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Christella dentata Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/christella-dentata/ (Date website was queried)