Alan Liefting
2004-10-24 20:19:43 UTC
http://arc.govt.nz/arc/index.cfm?ADC408DC-BCD4-1A24-9C1E-75698BA9D6B9
18 October 2004
New research into three popular garden plants has raised serious
concerns about their potential to invade and take over natural ecosystems.
The three species researched were agapanthus (Agapanthus praecox
subspecies orientalis and praecox and their hybrids and cultivars),
phoenix palm (Phoenix canariensis) and English ivy (Hedera helix
subspecies helix and cultivars). The study looked at the distances
plants could spread unassisted, the range of habitats they were capable
of invading and what impacts they were having on parkland and other
natural areas.
All three species were found to be invasive in a range of ecosystems, to
spread into remote and inaccessible areas and to have significant
environmental impacts on natural areas they invade.
Auckland Regional Council Biosecurity Manager Jack Craw says the
research, commissioned by the ARC, confirms what was already suspected
in terms of agapanthus and ivy, but that the invasive capabilities of
phoenix palm comes as an unwelcome wake-up call.
“When we started looking, we found phoenix palms everywhere: half-grown
palms that had self-sown into mangrove wetlands, young plants growing in
thick kikuyu on the edges of farm paddocks, even seedlings growing
alongside native nikau palm seedlings in dense bush,” Mr Craw says.
“These plants are being spread into some of our most remote and
vulnerable habitats by birds, wind and water. All three species are
becoming significant weeds in natural areas.”
Mr Craw is urging developers and gardeners to consider replacing
agapanthus, phoenix palm and English ivy with non-invasive alternatives.
Information on how to control invasive weeds, and some suggested
non-invasive alternatives to replace problem weeds, is available from
the ARC by phoning 09 366 2000.
For more information please call:
Jack Craw, ARC Biosecurity Manager, 366 2000 ext 8771 or 021 222 9064.
Simon Roche, ARC Communications, 366 2000 ext 8100 or 021 656 380.
Background information
Weeds in Auckland
* A previous study by Esler found that, between pre-1840 and 1985,
introduced plants naturalised in Auckland City at the average rate
of one species every 88 days. New plant species continue to
naturalise in Auckland and wider New Zealand. The rate of
naturalisation appears to be increasing, mainly due to the
increased rate of new plants coming onto the garden plant market.
* New Zealand has more naturalised exotic plants (just over 2,000)
than native species (around 2,000). Some are useful for primary
production. Many co-exist at low levels and have minimal economic,
ecological or health impacts. A small percentage have become
significant weeds. Invasive species that naturalised a number of
years ago, such as gorse, are generally well recognised as weeds.
It may take a number of years to determine whether plants that
have naturalised more recently will be invasive or not.
* There are also around 27,500 further plant species that have been
introduced to New Zealand, but which have not yet naturalised (ie
produced viable offspring unassisted in the wild). A small
proportion of these will naturalise in the future. Most will have
minimal impacts, but an estimated 10-20 per cent of plants that
naturalise will become serious weeds.
* Auckland has the dubious distinction of being the weediest city in
the world.
Agapanthus
Agapanthus praecox subspecies orientalis and praecox, also cultivars and
hybrids of these 2 subspecies.
* This includes all large agapanthus types.
* Found to invade a range of habitat types, including roadside
drains, low scrub, regenerating bush, forest margins, pasture,
coastal and beachfront vegetation, sand dunes, coastal cliffs,
rocky inland cliffs, exposed coastal areas, pastoral streams,
gardens (very common, both planted and naturalised).
* Forms dense monocultures that exclude all other species: one cliff
infestation at Piha was found to cover an area of over 1,000m2.
* Seeds were found to blow an average of 17.3m.
* Some of the new dwarf agapanthus cultivars do not readily set seed
and can be safely planted. ARC is liaising with growers to
establish which of the dwarf cultivars are safe and which are not.
* Those looking for non-invasive alternatives to agapanthus could
try clivia (similar foliage to agapanthus and a range of
attractive, large, colourful flowers), native rengarenga (widely
available with foliage similar to agapanthus and sprays of small
white flowers in summer), native coastal grasses such as pingao or
spinifex (great for stabilising coastal dunes and helping conserve
endangered native pingao), native toetoe grasses and gahnia (good
erosion control for sunny and shady sandy inland sites) or one of
the many varieties of native flax (hardy for dry sites in full sun
and helps stabilise sandy or unstable sites).
Ivy
Hedera helix subspecies helix - English ivy
* English Ivy was found invading all age classes of native forest,
pine forests, roadsides, forest margins and gardens. Bird-spread
seedlings are becoming common in many local reserves. Ivy
infestations in regional parks tended to originate from past house
sites.
* Infestations up to 160m2 were recorded. Ivy cover reached 100 per
cent in many places, completely excluding all other species. In
some cases, mature trees had collapsed under the weight of ivy vines.
* Another common ivy type, Canary Island ivy, Hedera helix
subspecies canariensis, was not found to be invasive. Although a
large mature Canary Island ivy vine with masses of flowers and
buds was found in the suburb of Morningside, Auckland, there has
only been one record of a naturalised Canary Island ivy in New
Zealand.
Phoenix palm
Phoenix canariensis
* Seeds are mostly spread by water, but also by birds. One
naturalised palm was found growing over 1km from the nearest
possible source.
* Phoenix palm was found invading a range of habitats, including
coastal (phoenix is salt tolerant) and dense bush. A couple of
naturalised palms were growing well in dense kikuyu grass. Small
phoenix palm seedlings are virtually indistinguishable from native
nikau seedlings, meaning that the full extent to which phoenix
palms are spreading into forest areas may not be realised for some
time.
* Landcare Research has classified phoenix palm as a ‘sleeper weed’
- a plant that spreads slowly and goes unnoticed until it becomes
widespread.
* Phoenix palm is already recognised as being invasive in parts of
Australia and America that have similar climates to New Zealand.
It is invasive in creek lands in Melbourne, very common in New
South Wales and has naturalised in northern Victoria and some
areas of Western Australia. The California Invasive Plant Council
has advised that phoenix palm will be included on their next
invasive plants list, due out before the end of 2004.
* The robust, sharp spines can cause severe injuries. 21 children
were admitted to Starship with phoenix injuries between 1992 and
1997. Over the same period, 8.4 per cent of all foreign body
injuries were identified as phoenix palm incidents.
* New Zealand has only one species of native palm; nikau palm
(Rhopalostylis sapida), which is found nowhere else in the world.
18 October 2004
New research into three popular garden plants has raised serious
concerns about their potential to invade and take over natural ecosystems.
The three species researched were agapanthus (Agapanthus praecox
subspecies orientalis and praecox and their hybrids and cultivars),
phoenix palm (Phoenix canariensis) and English ivy (Hedera helix
subspecies helix and cultivars). The study looked at the distances
plants could spread unassisted, the range of habitats they were capable
of invading and what impacts they were having on parkland and other
natural areas.
All three species were found to be invasive in a range of ecosystems, to
spread into remote and inaccessible areas and to have significant
environmental impacts on natural areas they invade.
Auckland Regional Council Biosecurity Manager Jack Craw says the
research, commissioned by the ARC, confirms what was already suspected
in terms of agapanthus and ivy, but that the invasive capabilities of
phoenix palm comes as an unwelcome wake-up call.
“When we started looking, we found phoenix palms everywhere: half-grown
palms that had self-sown into mangrove wetlands, young plants growing in
thick kikuyu on the edges of farm paddocks, even seedlings growing
alongside native nikau palm seedlings in dense bush,” Mr Craw says.
“These plants are being spread into some of our most remote and
vulnerable habitats by birds, wind and water. All three species are
becoming significant weeds in natural areas.”
Mr Craw is urging developers and gardeners to consider replacing
agapanthus, phoenix palm and English ivy with non-invasive alternatives.
Information on how to control invasive weeds, and some suggested
non-invasive alternatives to replace problem weeds, is available from
the ARC by phoning 09 366 2000.
For more information please call:
Jack Craw, ARC Biosecurity Manager, 366 2000 ext 8771 or 021 222 9064.
Simon Roche, ARC Communications, 366 2000 ext 8100 or 021 656 380.
Background information
Weeds in Auckland
* A previous study by Esler found that, between pre-1840 and 1985,
introduced plants naturalised in Auckland City at the average rate
of one species every 88 days. New plant species continue to
naturalise in Auckland and wider New Zealand. The rate of
naturalisation appears to be increasing, mainly due to the
increased rate of new plants coming onto the garden plant market.
* New Zealand has more naturalised exotic plants (just over 2,000)
than native species (around 2,000). Some are useful for primary
production. Many co-exist at low levels and have minimal economic,
ecological or health impacts. A small percentage have become
significant weeds. Invasive species that naturalised a number of
years ago, such as gorse, are generally well recognised as weeds.
It may take a number of years to determine whether plants that
have naturalised more recently will be invasive or not.
* There are also around 27,500 further plant species that have been
introduced to New Zealand, but which have not yet naturalised (ie
produced viable offspring unassisted in the wild). A small
proportion of these will naturalise in the future. Most will have
minimal impacts, but an estimated 10-20 per cent of plants that
naturalise will become serious weeds.
* Auckland has the dubious distinction of being the weediest city in
the world.
Agapanthus
Agapanthus praecox subspecies orientalis and praecox, also cultivars and
hybrids of these 2 subspecies.
* This includes all large agapanthus types.
* Found to invade a range of habitat types, including roadside
drains, low scrub, regenerating bush, forest margins, pasture,
coastal and beachfront vegetation, sand dunes, coastal cliffs,
rocky inland cliffs, exposed coastal areas, pastoral streams,
gardens (very common, both planted and naturalised).
* Forms dense monocultures that exclude all other species: one cliff
infestation at Piha was found to cover an area of over 1,000m2.
* Seeds were found to blow an average of 17.3m.
* Some of the new dwarf agapanthus cultivars do not readily set seed
and can be safely planted. ARC is liaising with growers to
establish which of the dwarf cultivars are safe and which are not.
* Those looking for non-invasive alternatives to agapanthus could
try clivia (similar foliage to agapanthus and a range of
attractive, large, colourful flowers), native rengarenga (widely
available with foliage similar to agapanthus and sprays of small
white flowers in summer), native coastal grasses such as pingao or
spinifex (great for stabilising coastal dunes and helping conserve
endangered native pingao), native toetoe grasses and gahnia (good
erosion control for sunny and shady sandy inland sites) or one of
the many varieties of native flax (hardy for dry sites in full sun
and helps stabilise sandy or unstable sites).
Ivy
Hedera helix subspecies helix - English ivy
* English Ivy was found invading all age classes of native forest,
pine forests, roadsides, forest margins and gardens. Bird-spread
seedlings are becoming common in many local reserves. Ivy
infestations in regional parks tended to originate from past house
sites.
* Infestations up to 160m2 were recorded. Ivy cover reached 100 per
cent in many places, completely excluding all other species. In
some cases, mature trees had collapsed under the weight of ivy vines.
* Another common ivy type, Canary Island ivy, Hedera helix
subspecies canariensis, was not found to be invasive. Although a
large mature Canary Island ivy vine with masses of flowers and
buds was found in the suburb of Morningside, Auckland, there has
only been one record of a naturalised Canary Island ivy in New
Zealand.
Phoenix palm
Phoenix canariensis
* Seeds are mostly spread by water, but also by birds. One
naturalised palm was found growing over 1km from the nearest
possible source.
* Phoenix palm was found invading a range of habitats, including
coastal (phoenix is salt tolerant) and dense bush. A couple of
naturalised palms were growing well in dense kikuyu grass. Small
phoenix palm seedlings are virtually indistinguishable from native
nikau seedlings, meaning that the full extent to which phoenix
palms are spreading into forest areas may not be realised for some
time.
* Landcare Research has classified phoenix palm as a ‘sleeper weed’
- a plant that spreads slowly and goes unnoticed until it becomes
widespread.
* Phoenix palm is already recognised as being invasive in parts of
Australia and America that have similar climates to New Zealand.
It is invasive in creek lands in Melbourne, very common in New
South Wales and has naturalised in northern Victoria and some
areas of Western Australia. The California Invasive Plant Council
has advised that phoenix palm will be included on their next
invasive plants list, due out before the end of 2004.
* The robust, sharp spines can cause severe injuries. 21 children
were admitted to Starship with phoenix injuries between 1992 and
1997. Over the same period, 8.4 per cent of all foreign body
injuries were identified as phoenix palm incidents.
* New Zealand has only one species of native palm; nikau palm
(Rhopalostylis sapida), which is found nowhere else in the world.