Phormium tenax (New Zealand flax)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Plant Type
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Hosts/Species Affected
- Biology and Ecology
- Latitude/Altitude Ranges
- Air Temperature
- Rainfall Regime
- Soil Tolerances
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Pathway Causes
- Impact Summary
- Economic Impact
- Environmental Impact
- Threatened Species
- Risk and Impact Factors
- Uses List
- Similarities to Other Species/Conditions
- Prevention and Control
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Phormium tenax J.R.Forst. & G.Forst.
Preferred Common Name
- New Zealand flax
Other Scientific Names
- Chlamydia tenacissima Gaertn.
- Lachenalia ramosa Lam.
- Phormium ramosum (Lam.) Billb.
- Phormium tenax f. atropurpureum Voss
International Common Names
- English: flax (New Zealand)
- Spanish: formio lino de la Nueva Zelandia
- French: lin de Nouvelle Zelande
Local Common Names
- Brazil: canhamo de Nova-Zelandia; espadana; espadao; fórmio
- Germany: Neuseelandflachs; Neuseeländischer flachs
- Guatemala: madre de henequén
- Italy: clamidia; lino della Nuova Zelande
- Japan: niusai ran
- Netherlands: Nieuwzeelands vlas; Nieuw-Zeelands Vlas
- New Zealand: harakeke; korare; korari
- Portugal: atadeira; marradeira
- Spain: formio; lino de espada
- Sweden: Nyzeelandskt lin
- UK: flax lily; New Zealand hemp
- PHMTE (Phormium tenax)
Summary of InvasivenessTop of page
P. tenax is an evergreen perennial plant native to New Zealand, and formerly important as a fibre crop. It has proved seriously invasive on the three remote islands of the Tristan da Cunha archipelago in the central South Atlantic Ocean (Ryan et al., 2012), and on the equally isolated island of St. Helena (ISSG, 2016). Shepherd (2013) says it is also invasive on the Juan Fernandez Islands near Chile, and on Molokai Island in Hawaii. It is a robust, fast-growing species, dispersed both by seeds and by vegetative reproduction, and the vegetative spread means that once established the life-span is potentially unlimited.
On mainland Australia, P. tenax is regarded as an environmental weed in Tasmania and Victoria, and as a potential environmental weed in other parts of southern Australia (Csurhes and Edwards, 1988; Weeds of Australia, 2016). It has spread in some other places where it has been introduced, such as Hawaii and Chile, but in many other countries where Hanelt (2001) says that P. tenax was once planted, (North and East Africa, Mexico, Uruguay, Brazil, southern Europe, India, Java, Japan, Taiwan) internet searches in 2016 could find little evidence of any plants surviving to the present day.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Monocotyledonae
- Order: Liliales
- Family: Agavaceae
- Genus: Phormium
- Species: Phormium tenax
Notes on Taxonomy and NomenclatureTop of page
Phormium is a genus of two plant species in the Xanthorrhoeaceae family. This family, as defined by the Angiosperm Phylogeny Group in 2009 (the APG III system), contains three subfamilies: Phormium is in the subfamily Hemerocallidoideae. The family includes 1236 species recognized by the Plant List (2013). Phormium includes two species, P. cookianum (synonym P. colensoi) and P. tenax.P. tenax occurs naturally in New Zealand and Norfolk Island, while P. cookianum is endemic to New Zealand. The name Phormium comes from Ancient Greek for "basket", while tenax was Latin for "strong".
NZPCN (2016) says that many botanists suggest that plants from the Chatham Islands could be separated at species rank from the mainland New Zealand species, but Smissen and Heenan (2010) conclude that as the morphological divergence is slight and difficult to quantify, neither species nor subspecies rank is appropriate for the Chatham Island populations. Other distinctive variants occur on the Three Kings and outer Hauraki Gulf Islands and along the Kaikoura coast. Norfolk Island P. tenax (which possibly originated in New Zealand, as claimed by Coyne, 2009) also differs in subtle ways from New Zealand forms. Further study into this variation is underway.
While many botanists have adopted the APG III system of classification for the orders and families of flowering plants, the CAB Thesaurus continues to use the Cronquist system. Phormium formerly belonged to the family Agavaceae and many classification systems still place it there. The current taxonomic tree on this datasheet reflects this earlier taxonomic placement. However, Wehi and Clarkson (2007) list a number of differences between Phormium spp. and other Agavaceae, and suggest that superficial similarities between Phormium and other members of the family result from convergent evolution and not shared ancestry.
DescriptionTop of page
The following is modified from Moore and Edgar (1970): Leaves 1–3 m long by 5–12 cm wide, stiff and more or less erect, at least in the lower part; base heavy and usually brightly coloured. Inflorescence up to 5 or even 6 m tall. Flower stem about 2–3 cm in diameter, usually erect, dark, cylindrical in cross-section, hairless. Flowers 2.5–5 cm long, mostly dull red, the tips of the inner tepals only slightly recurved. Ovary erect, carpels straight. Capsule usually less than 10 cm long, often much less, erect, three-angled, abruptly narrowed to the tip, not twisted, remaining firm and dark in age. Seeds about 9–10 × 4–5 mm, more or less elliptical, plate-like but more or less twisted.
Plant TypeTop of page Herbaceous
DistributionTop of page
The native range of P. tenax is limited to New Zealand and possibly Norfolk Island, although Coyne (2009) suggests that it may have been introduced here 600-800 years ago. Distribution within New Zealand is detailed by Wehi and Clarkson (2007). It is present in Australia, where it is naturalized in Tasmania and sparingly naturalized in southeastern South Australia and eastern New South Wales. It has been introduced to parts of South America, and seems to have spread to some extent in Chile (Chileflora, 2016). Although probably introduced to the UK perhaps 200 years ago, the species has not proved very invasive in that environment, since it is mentioned by Stace (2010) as ‘very persistent where planted on cliffs or rocky places by the sea; very scattered in south and west Britain, Ireland, Isle of Man and the Channel Islands, self-sown mainly in Scilly’. Other countries where it has been cultivated include the USA, Mexico and South Africa (see Distribution Table for details).
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|India||Present only in captivity/cultivation||Introduced||Not invasive||Hanelt et al., 2001|
|Indonesia||Present||Present based on regional distribution.|
|-Java||Present only in captivity/cultivation||Introduced||Not invasive||Hanelt et al., 2001|
|Japan||Present only in captivity/cultivation||Introduced||Not invasive||Hanelt et al., 2001|
|Singapore||Present only in captivity/cultivation||Introduced||Not invasive||PIER, 2016|
|Taiwan||Present only in captivity/cultivation||Introduced||Not invasive||Hanelt et al., 2001|
|South Africa||Present only in captivity/cultivation||Introduced||Not invasive||Hanelt et al., 2001|
|Mexico||Present only in captivity/cultivation||Introduced||Not invasive||Hanelt et al., 2001|
|USA||Present only in captivity/cultivation||Introduced||Hanelt et al., 2001||Available from nurseries|
|-Hawaii||Localised||Introduced||Invasive||PIER, 2016||Dense thickets in gullies in mesic areas below 300m on Hawai’I, Kaua’I, Moloka’i|
|Argentina||Present only in captivity/cultivation||Introduced||Not invasive||Hanelt et al., 2001|
|Brazil||Present only in captivity/cultivation||Introduced||Not invasive||Hanelt et al., 2001|
|Chile||Localised||Introduced||Invasive||Chileflora, 2016||Low altitude interior valleys; coastal mountains 500-2000m; coastal areas, 0-500m. Dry arid areas with drought period of 6-10 months, 100-300mm rain, in winter.|
|Uruguay||Present only in captivity/cultivation||Introduced||Not invasive||Hanelt et al., 2001|
|Portugal||Present||Present based on regional distribution.|
|UK||Localised||Introduced||Invasive||Stace, 2010||Very scattered S&W Britain, Ireland, Isle of Man, Channel Islands. Available from websites.|
|Australia||Present||Introduced||Council of Heads of Australasian Herbaria, 2016||Cultivated by CSIRO in the Black Mountains of Australian Capital Territory in 1965|
|-New South Wales||Localised||Introduced||Invasive||Weeds of Australia, 2016||Sparingly naturalised in eastern areas|
|-South Australia||Localised||Introduced||Invasive||Weeds of Australia, 2016||Sparingly naturalised in south-east|
|-Victoria||Localised||Introduced||Invasive||Carr et al., 1992||Freshwater wetands|
|New Zealand||Widespread||Native||Invasive||Moore and Edgar, 1970|
|Norfolk Island||Widespread||Coyne, 2009; NZPCN, 2016||Probably native|
History of Introduction and SpreadTop of page
Spread of P. tenax from country to country has almost certainly been entirely by people. Even the presence of the species on Norfolk Island, where it has always been considered native, has now been suggested by Coyne (2009) to be the result of its introduction there by Polynesian sailors. Elsewhere, where it has become naturalized (the UK, Tristan da Cunha, St. Helena, Hawaii, Chile), it was deliberately planted as a curiosity or as a potential crop species. In Argentina the species was introduced by the New Zealander AA Cameron (McClintoch, 1966). On the Falkland Islands, too, it was introduced and is now said to be a ‘cultivated ornamental, very rare’ (Falklands Conservation, 2016).
In the Tristan da Cunha archipelago, P. tenax was introduced to the main island of Tristan in the 1800s for fibre and roofing. Although no longer used for these purposes it is widely planted around the island’s only settlement as a windbreak. It has spread from there to other areas. It was then introduced to Inaccessible Island in the 1920s and has now spread over a considerable area of the island. It was also introduced to Nightingale Island at an unknown date and has spread there to some extent. Ryan et al. (2012) says that even in those environments, it is ‘not an aggressive invader’. On St. Helena the first flax mill was opened in 1874 but the last mill closed in 1966, leaving 3000 acres (over 1200 ha) of P. tenax, which remains an environmental issue today (St. Helena info, 2016).
IntroductionsTop of page
|Introduced to||Introduced from||Year||Reason||Introduced by||Established in wild through||References||Notes|
|Natural reproduction||Continuous restocking|
|Australia||New Zealand||1965||Horticulture (pathway cause)||Government||Council of Heads of Australasian Herbaria (2016)||Planted by CSIRO|
|UK||New Zealand||1920||Horticulture (pathway cause)||Stace (2010)|
Risk of IntroductionTop of page
The risk of introduction to new countries other than by human means is extremely slight and its spread from existing introductions will probably be slow.
HabitatTop of page
P. tenax mostly grows in seasonally waterlogged swamps or in intermittently flooded land, but it also thrives on coastal cliffs and in well-drained gardens where, at least in New Zealand, its many decorative forms are extremely popular landscape features. In recent years it has also been used in mass plantings at the side of roads. By contrast, Duncan et al. (1990) said that although P. tenax favours good drainage it does not require much soil depth. This explains its colonization of poorly drained sites such as dune hollows.
P. tenax is no longer as widespread in New Zealand as it once was. Drainage of wetlands, channeling of rivers and clearance of native vegetation for agriculture or forestry have meant that nowadays it is mostly found in national parks and reserves (McGruddy, 2006), although selected and often multi-coloured cultivated plants occur in many gardens.
In Hawaii, Smith (2016) says: ‘The species is found principally in gullies in mesic areas below 300 m, e.g. Moloka'i, and the northern Hamakua coastline, Hawai'i.’ Shepherd (2013) adds that on Molokai Island it has invaded high elevation rainforest. In Chile, Chileflora (2016) records its distribution as: low altitude, interior valleys; Coastal mountains, 500 - 2000 m; Coastal areas, 0 - 500 m, but gives no further detail. The distribution shown on the website indicates the species is found in the temperate Mediterranean climatic zone, with rainfall that increases southwards and in the mountains.
Habitat ListTop of page
|Rivers / streams||Principal habitat||Natural|
|Coastal areas||Principal habitat||Natural|
|Cultivated / agricultural land||Secondary/tolerated habitat||Natural|
|Cultivated / agricultural land||Secondary/tolerated habitat||Productive/non-natural|
|semi-natural/Scrub / shrublands||Principal habitat||Natural|
Hosts/Species AffectedTop of page
On St. Helena where P. tenax was grown as a major crop plant until the mid 1960s, the IUCN Red List (IUCN, 2016) lists the following native species as endangered as a result of the presence of P. tenax, or due to the historic clearance of vegetation for the crop: Elaphoglossum dimorphum, toothed tongue fern (critically endangered); Wahlenbergia linifolia, small bellflower (critically endangered); Nesohedyotis arborea, dogwood (endangered); Pladaroxylon leucadendron, he cabbage tree (critically endangered); Melanodendron integrifolium, black cabbage tree (vulnerable); Commidendrum spurium, false gumwood (critically endangered); and Lachanodes arborea, she cabbage tree (critically endangered).
Biology and EcologyTop of page
McGruddy (2006) gives the summary: ‘Harakeke [P. tenax] is robust, fast-growing, wind-tolerant, flood-tolerant, drought-tolerant, light-tolerant, frost-tolerant’.
Chromosome number is 2n=32 (Moore and Edgar, 1970).
The flowers of P. tenax are bisexual and protandrous, meaning that the pollen matures before the stigma is receptive. A large quantity of waxy, orange coloured pollen is produced (Wehi and Clarkson, 2007). This pollen is both light and powdery. The flowers produce abundant nectar which is readily consumed by honey-eating birds such as tui (Prosthemadera novaeseelandiae) and bellbirds (Anthornis melanura) (Craig and Stewart, 1988), but high annual variability in flowering makes nectar an unreliable food source. These and other birds, including stitchbirds (Notiomystis cincta), kaka (Nestor meridionalis), kakariki (Cyanoramphus spp.) and whiteyes (Zosterops lateralis novaeseelandiae) collect nectar and whilst doing so pick up pollen on their feathers and carry it from flower to flower (Wehi and Richardson, 2007). Non-native birds like starlings (Sturnus vulgaris) and blackbirds (Turdus merula) are also believed to act as pollinators (Sparrow, 1965). However, wind, water, bees and other insects have also been suggested as pollinating agents (Wehi and Clarkson, 2007).
Seed matures in March (McGruddy, 2006), and seeds are released by explosive dehiscence of the seed capsules. Water is the most likely method of dispersal although the seed is light and may be blown by the wind for some distance. Seeds initially show some dormancy and this can be broken by stratification (Mackay et al., 2002).
Annual variation in flowering and seed production are typical of mast seeding, whereby the variation in seed production may reduce seed loss to predators, although there are many other hypotheses to explain its possible ecological and evolutionary advantages (Kelly, 1994).
P. tenax also reproduces vegetatively by the production of ramets from underground rhizomes so that large plants can have as many as 3200 ramets (Wehi and Clarkson, 2007).
Presumably, since individual plants of P. tenax can reproduce indefinitely by vegetative means, their life-span is unlimited. As one cluster of leaves flowers and then dies, several new leaf clusters arise around the old flower stem.
According to McGruddy (2006), ‘Flax is relatively slow growing in the first two years, but will begin rapidly bulking up from the third year. A seedling plant three years old may have up to 15 fans [each a sheath of up to 10 leaves]. Fans will begin flowering, generally, from about the 5th year. After flowering, that fan dies, with up to three new fans growing around the flower stalk. An older bush will tend to take on a ring form, with younger fans encircling an empty area in the centre (where older fans have died).’
Leaf growth is reported to be slower at cool sites, especially in the presence of drought, low soil fertility and competition from other plants.
Plants flower from late October through to February (Wehi and Clarkson, 2007).
Population Size and Structure
P. tenax was once very widespread in New Zealand but drainage of wetlands and other landscape modifications have meant that it is much less common than it once was (McGruddy, 2006).
Rich, well-drained alluvial and peat soils encourage abundant growth (Rigg and Watson, 1945). In Pakihi soils, which are of low pH and support herbaceous heathland, the application of phosphate and potassium resulted in improved root and leaf development of P. tenax (Rigg and Watson, 1945).
The root system of a New Zealand flax bush ‘may extend as wide and deep as the height of the bush (3+ m) with perhaps the bulk of the roots in the top 50 cm, and in a radius 1.5 m from the centre of the bush' (McGruddy, 2006). ‘Stout orange roots extend parallel. Diagonal and vertical to the surface; with the upper layers branching into networks of fine, white roots’ (McGruddy, 2006).
Trials have shown that P. tenax accumulates significant quantities of potassium, variable quantities of nitrogen and low levels of phosphorus (McGruddy, 2006).
Wehi and Clarkson (2007) describe P. tenax as a significant component of three main community classes in its native environment: coastal cliffs, slopes and dunelands; estuarine shrublands; and lake margins and freshwater communities. They go on to describe the other species associated with it.
In its natural environment, P. tenax typically grows in wetter areas, on a wide range of substrates. It responds well to flowing water and periodic flooding, but both ongoing waterlogging and drought can have negative effects (Wehi and Clarkson, 2007). The same authors say that this species is one of the few New Zealand plants that recovers well after fire.
Although P. tenax is commonly found growing in wet areas, it can have too much water. Sorrell et al. (2001) grew plants in three depths of water. When water was 10 cm below substrate all plants survived, but only 60% of plants survived when the water was at the substrate surface. Sorrel et al. (2012) subjected P. tenax and two other New Zealand-native wetland species (Carex secta, Typha orientalis) to 9 depths of water between 0 and 0.5 m, after they had spent eight autumn-winter-spring months outdoors in waterlogged soil but without standing water. P. tenax growth decreased rapidly in standing water less than 0.25 m deep. This decrease in growth was associated with a decrease in the number of leaves produced per ramet. These authors reported that P. tenax has aerenchymatous shoots and roots, but root porosity is much lower (less than 20%) in P. tenax compared with the other two species (ca. 40–50% porosity).
McGruddy (2006) says that ‘Flax researchers all converge on the requirements for flax for fertile, well-drained soils; agree on the critical importance of the water-table; and describe the value of periodic floods in building up mulch around the base of the plant, and in washing away insect pests.’ Yeats (1948) is quoted in McGruddy (2006), as writing of ‘the misconception as to the need or preference of flax for wet land. In general it can be said that poor sub-soil drainage is one of the most frequent causes of poor growth and disease in flax.’
The species is very tolerant of salt spray, especially once it is past the seedling stage (Wehi and Clarkson, 2007).
ClimateTop of page
|Cf - Warm temperate climate, wet all year||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year|
|Cs - Warm temperate climate with dry summer||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers|
Latitude/Altitude RangesTop of page
|Latitude North (°N)||Latitude South (°S)||Altitude Lower (m)||Altitude Upper (m)|
Air TemperatureTop of page
|Parameter||Lower limit||Upper limit|
|Mean annual temperature (ºC)||8||19|
|Mean maximum temperature of hottest month (ºC)||11||22|
|Mean minimum temperature of coldest month (ºC)||3||16|
RainfallTop of page
|Parameter||Lower limit||Upper limit||Description|
|Mean annual rainfall||508||4330||mm; lower/upper limits|
Rainfall RegimeTop of page Uniform
Soil TolerancesTop of page
- seasonally waterlogged
Notes on Natural EnemiesTop of page
Because of the previous value of P. tenax as a commercial source of fibre, pests and diseases have been extensively investigated in New Zealand.
Scheele (1997, 2016) reports that yellow-leaf is the most serious disease and that various fungal infections (moulds and spots) can affect the appearance of P. tenax leaves. P. tenax is home to two native moths as well as mealy bugs and scale insects.
‘Yellow-leaf’ is characterised by abnormal yellowing of the leaves: the ‘growth of young leaves may be stunted and eventually the whole plant may collapse. Underground, the roots die off, the rhizome tissues collapse and rot spreads towards the crown of the plant’ (Scheele, 1997). The causative agent is a phytoplasma, transmitted by the native flax plant hopper (Zeoliarus atkinsoni) which injects the causative agent into the leaf, while sucking the sap. There seems little doubt that growing P. tenax in monoculture plantations, often on modified, drained soils contributed to the increased incidence of pests and diseases found on the crop.
The flax looper caterpillar (Orthoclydon praefactata), native to New Zealand, feeds at night on the underside of P. tenax leaves, leaving a ‘window’ of the leaf cuticle. The flax notcher moth (Tmeolphota steropastis), also native to New Zealand and a nocturnal feeder, leaves notches at the edges of young leaves (Scheele, 2016).
Mealy bugs occur where the leaves sheath together at the bottom of the fan and on the rhizome, often amongst masses of whitish-grey powder. One of these is the flax mealy bug (Balanococcus diminutus). They do not usually affect the health of the plant, but if the infestation is bad, the leaves develop a red colour (Scheele, 2016).
Scale insects, including Poliapsis and Pseudaulacaspis spp., form crusty, white, woolly patches on the underside of the leaves, especially in the shade. They suck the sap, discolour and weaken the leaves, making them more susceptible to diseases (Scheele, 2016).
Many fungal infections (moulds and spots) affect the appearance of the leaves and can discolour, weaken and break the fibres.
Although less than ‘natural’ enemies in New Zealand, since they were introduced, cattle and deer and goats will also eat P. tenax leaves (McGruddy, 2006).
Means of Movement and DispersalTop of page
Although P. tenax reproduces by both seed and vegetative reproduction it does not seem to be an aggressive invader. Vegetative reproduction only succeeds in helping individual plants expand their size. International carriage of either seed or ramets has been entirely by humans.
Natural Dispersal (Non-Biotic)
Seed capsules dehisce explosively and water dispersal is probably a major method by which the seeds are spread (Jesson et al., 2006). The seeds are also quite light and could be blown some distance by the wind (Wehi and Clarkson, 2007).
People have been the main agency by which the species has spread internationally and possibly within countries too. P. tenax has been deliberately introduced to many countries from its native habitat in New Zealand. From there it seems to have been taken to Australia, to Europe, North and South America, and Asia (Hanelt, 2001). The reason for its introduction has either been as a crop for fibre production or for its ornamental value as a distinctive garden plant.
Pathway CausesTop of page
Impact SummaryTop of page
|Environment (generally)||Positive and negative|
Economic ImpactTop of page
Presumably in at least some of the countries to which P. tenax has been taken it provided some economic benefits as a crop plant, although little has been reported on such benefits except in St. Helena (St. Helena info, 2016).
Environmental ImpactTop of page
Although P. tenax has been introduced to several countries outside its native land of New Zealand, either as a crop or as an ornamental, the species seems to have had few adverse effects except on the remote islands of Tristan da Cunha and St. Helena and their associated islands. Impacts on native species in these locations have been described by Ryan et al. (2012) and St. Helena info (2016). It is also recognized as being present in ecosystems in Chile (Chileflora, 2016) and Hawaii (PIER, 2016) although its impacts do not seem to have been described. P. tenax has been described as a potential invasive species in Australia (Weeds of Australia, 2016), but little information on effects on native environments is available.
Impact on Habitats
Although mentioned as having been planted in a number of overseas countries, there is little information on its effects on habitats apart from its threatening native species in Tristan da Cunha (Ryan et al, 2012) and its residual effects on the vegetation of St. Helena (St. Helena info, 2016). The impact on native plant communities has also been reported as reducing suitable habitat for native bird species on St. Helena, negatively impacting two species of buntings classed as vulnerable by the IUCN (ISSG, 2016; IUCN, 2016).
Impact on Biodiversity
P. tenax colonizes and converts native habitats, degrading them and making them less suitable for native species (ISSG, 2016.). In St. Helena, it is listed as threatening a number of endangered plant species: see Threatened Species table for details.
Threatened SpeciesTop of page
|Threatened Species||Conservation Status||Where Threatened||Mechanism||References||Notes|
|Commidendrum spurium (false gumwood)||CR (IUCN red list: Critically endangered) CR (IUCN red list: Critically endangered)||Saint Helena||IUCN, 2016|
|Elaphoglossum dimorphum (toothed tongue fern)||CR (IUCN red list: Critically endangered) CR (IUCN red list: Critically endangered)||Saint Helena||IUCN, 2016|
|Lachanodes arborea (she cabbage tree)||CR (IUCN red list: Critically endangered) CR (IUCN red list: Critically endangered)||Saint Helena||IUCN, 2016|
|Melanodendron integrifolium (black cabbage tree)||VU (IUCN red list: Vulnerable) VU (IUCN red list: Vulnerable)||Saint Helena||IUCN, 2016|
|Nesohedyotis arborea (St Helena Dogwood)||EN (IUCN red list: Endangered) EN (IUCN red list: Endangered)||Saint Helena||IUCN, 2016|
|Pladaroxylon leucadendron (he cabbage tree)||CR (IUCN red list: Critically endangered) CR (IUCN red list: Critically endangered)||Saint Helena||IUCN, 2016|
|Wahlenbergia linifolia (large bellflower)||CR (IUCN red list: Critically endangered) CR (IUCN red list: Critically endangered)||Saint Helena||IUCN, 2016|
Risk and Impact FactorsTop of page Invasiveness
- Invasive in its native range
- Proved invasive outside its native range
- Abundant in its native range
- Pioneering in disturbed areas
- Benefits from human association (i.e. it is a human commensal)
- Long lived
- Reproduces asexually
- Has high genetic variability
- Ecosystem change/ habitat alteration
- Soil accretion
- Threat to/ loss of endangered species
- Competition - monopolizing resources
- Competition - shading
- Competition - smothering
- Highly likely to be transported internationally deliberately
- Difficult/costly to control
UsesTop of page
When Polynesian sailors, progenitors of the Maori, first settled in New Zealand about 800 years ago they quickly discovered the benefits of the native P. tenax, using its leaves and extracted fibres for clothing, cordage, fishing nets and snares, mats and containers. P. tenax is still a taonga (treasured) species for Maori and recent decades have seen a marked revival in both traditional and contemporary weaving practice. During the 1800s the arrival of Europeans and international commerce led to development of industries to extract, manufacture and export flax fibre. This export industry increased hugely after the invention of flax stripping machinery to extract the fibre. The industry reached its peak early in the twentieth century and then declined markedly, finally dying in the early 1970s with the removal of agricultural subsidies.
European and Maori entrepreneurs quickly learnt the benefits of the fibres of P. tenax and as early as 1828 considerable volumes of flax fibre were being exported to Sydney (McGruddy, 2006), all, at that stage, being hand-dressed. Not until the 1860s was machine dressing of the fibre developed. This sacrificed quality but enabled tonnages of flax to be processed, suitable for hard-wearing cordage and textiles. From then on New Zealand flax followed the boom and bust cycles of most agricultural commodities. These booms and busts are well described in Kete Horowhenua (2016), a report which describes in detail the history of the flax industry and its effects on the fluctuating fortunes of Foxton, a small Manawatu town.
The economic impact of P. tenax peaked during the First World War (1914-1918) when other sources of comparable fibre were scarce, and it then effectively died after the 1930s -1940s when it was supplanted by artificial fibres derived from oil and its derivatives. There has been something of a resurgence in recent years with increased interest in ‘natural’ fibres and in cosmetics based on flax.
McGruddy (2006) describes the renewed interest in products derived from P. tenax, including benefits of naturally grown flax fibre over synthetic fibres, the possible development of finer flax fibres than those usually used, its use in biocomposites, better flax-derived textiles, mats and carpets, for making paper, as a source of edible vegetable oil, and possible of phyto-medical extracts.
Plantation flax can be expected to yield 75-100 tonnes/ha of leaves (McGruddy, 2006).
Encyclopaedia Brittanica (2016) said: ‘It has been grown in southern Ireland, mainly as an ornamental plant, since 1798 and was later introduced to parts of Europe; commercial plantings were started in St. Helena, the Azores, Australia, southern Africa, and Japan. In the 1930s, cultivation was established in the South American countries of Brazil, Chile, and Argentina.’ Plants were also introduced to St. Helena and Tristan da Cunha, remote islands in the South Pacific and their flax industries thrived briefly before becoming uneconomic and dying out, leaving flax plants there as a threat to native environments.
On St. Helena the flax industry thrived from the time of the First World War (1914-1918), with prices for flax fibre reaching their zenith in 1951, when the area planted in flax reached over 3000 acres and the industry employed as many as 400 people (St. Helena info, 2016). The industry finally died in 1966, leaving many unemployed islanders and a legacy of P. tenax infestations.
P. tenax has, over the years, been of huge social and economic benefit to the Maori inhabitants of New Zealand. It was the most commonly used plant for weaving, with the leaf being plaited into mats, receptacles and bags; the fibre was woven into clothing, cordage and fishing nets (McGruddy, 2006). Maori developed a classification system of cultivars, probably based on the strength and quality of fibre. Besides uses for its leaves and fibre, flax also proved useful to the Maori in other ways. Decoctions of exudate at the leaf base were applied to severe wounds or burns, and for rheumatic or sciatic areas. Blanched leaf bases were sometimes pulped and then roasted to relieve tumours and abscesses, and juices from the roots used as purgatives (Wehi and Clarkson, 2007).
Maori Plant Use (2016) provides a large amount of information on the uses to which the Maori put P. tenax, from medical uses (applied to wounds, burns, scalds, for dysentery, healing chafed areas, for boils, intestinal worms and constipation, root extracts as a purgative and anthelmintic) through use of flax leaves for wound dressings, for extraction of fibre, paper manufacture, and clothing), to fishing nets, rafts, in canoe building, fishing lines and snares.
P. tenax was used as a roofing material and shelter plant in St. Helena and Tristan da Cunha. As an ornamental, it is commonly available in garden nurseries and is advertised on websites in the UK, North America, South Africa and elsewhere. Many different cultivars have been selected for a wide range of colours and colour combinations, making the species a striking addition to many gardens.
P. tenax provides food for and shelter for birds and reptiles native to New Zealand. The seed is eaten in quantities by the grey duck (Anas superciliosa): the nectar produced by the flowers provides food for native and some introduced birds as well as for geckos and short-tailed bats (McGruddy, 2006).
For riparian plantings along waterways in New Zealand, both councils and farmers often used willows (Salix spp.) but these have partly fallen into disrepute because they can become weedy and can block waterways. Interest in using native species, including P. tenax has been increasing in recent years. P. tenax has considerable advantages in such situations. If planted in flood zones its leaves are flattened by flood waters but will afterwards become erect again. The bulk of flax roots may be in the top 50 cm of the soil, but they can extend to 3 m below the surface in deep soils (McGruddy, 2006). Riparian plantings may also help in reducing nutrient runoff, a major source of contamination of rivers in New Zealand. However a study by Douglas (2005, cited in McGruddy, 2006) suggests that although flax takes up some nutrients its role in this aspect would not be a major driver to support its widespread planting.
P. tenax can also play a part in shelter belts, where it forms a low-growing, drought-tolerant evergreen. In several parts of New Zealand, the species has long been used as a component of farm shelter belts.
Reay and Norton (1999) reported on the benefits of P. tenax as a nurse plant for the regeneration of native trees from pasture in New Zealand. The same authors suggested the possibility of using the species for this purpose in restoration projects.
Uses ListTop of page
- Erosion control or dune stabilization
- Landscape improvement
- Sociocultural value
- Propagation material
- Seed trade
Similarities to Other Species/ConditionsTop of page
The only other species in the genus Phormium is P. cookianum (syn. P. colensoi), sometimes known as mountain flax. It is generally similar to P. tenax but differs in its capsules which are pendulous rather than erect, and round rather than 3-sided, with valves that are twisted and become pale and papery with age. P. tenax mostly occurs in lowland swamps and intermittently flooded land, whereas P. cookianum occurs on coastal cliffs and mountain slopes, often being dominant on shady faces in high country (Moore and Edgar, 1970).
Prevention and ControlTop of page
Eradication of P. tenax seems to have been largely successful on Nightingale and Inaccessible Islands of the Tristan da Cunha group (Ryan et al., 2012). In 2004, an eradication programme was started, using a combination of uprooting, cutting, crushing and spraying with herbicide (5% glyphosate). After the operation, established plants were confined to about 300 m of cliffs on Inaccessible Island, where the very steep terrain made access difficult. This attempted eradication was very labour intensive and probably expensive.
Plants can be dug out, although their roots sometimes penetrate deeply in good soils. Large plants can be winched or bulldozed out.
Most of the published work on herbicides for P. tenax refers to its tolerance to herbicides, because such work was based on the benefits of maintaining the plants for either their environmental benefits or value as a crop. McGruddy (2006) suggests that the tolerance of P. tenax to many commonly used herbicides can be seen as a virtue of the plant because it means that many such chemicals can be used to control weeds where the species is grown as a crop. She considers its tolerance to triclopyr herbicides being most important because such materials are commonly used for control of scrubweeds such as gorse and blackberry. P. tenax is, however, more sensitive to glyphosate although its precise tolerance has not been evaluated. If no wetting agent is used with glyphosate, plants are reported to be more tolerant. The species is apparently susceptible to metsulfuron-methyl based herbicides (Harrington, 2007).
Harrington and Schmitz (2007) tested herbicides for their safety on species used in environmental restoration work in New Zealand and found that metsulfuron-methyl at 6 g a.i. /100 L of water caused more damage to the closely related P. colensoi than the other herbicides tested, which included amitrole (400 g a.i. /100L) and glyphosate (270 g a.i. /100L). The rate of glyphosate used in Ryan et al.’s (2012) eradication attempts was much higher (5%) and was applied to the bases of cut leaves.
ReferencesTop of page
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ContributorsTop of page
26/04/2016 Original text by:
Ian Popay, Landcare Research, PB 3127, Hamilton 3240, New Zealand
Distribution MapsTop of page
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