Metrosideros excelsa Common name - New Zealand christmas tree, pohutukawa. Family - Myrtaceae. Synonym - Metrosideros tomentosa A. Rich.

Answer

Score

1.01

Is the species highly domesticated? (If answer is 'no' then go to question 2.01)

n

0

1.02

Has the species become naturalized where grown?

1.03

Does the species have weedy races?

2.01

Species suited to tropical or subtropical climate(s) (0-low; 1-intermediate; 2-high) – If island is primarily wet habitat, then substitute “wet tropical” for “tropical or subtropical”

1

2.02

Quality of climate match data (0-low; 1-intermediate; 2-high) see appendix 2

1

2.03

Broad climate suitability (environmental versatility)

n

0

2.04

Native or naturalized in regions with tropical or subtropical climates

n

0

2.05

Does the species have a history of repeated introductions outside its natural range? y=-2

y

3.01

Naturalized beyond native range y = 1*multiplier (see Append 2), n= question 2.05

y

1

3.02

Garden/amenity/disturbance weed y = 1*multiplier (see Append 2)

n

0

3.03

Agricultural/forestry/horticultural weed y = 2*multiplier (see Append 2)

n

0

3.04

Environmental weed y = 2*multiplier (see Append 2)

y

2

3.05

Congeneric weed y = 1*multiplier (see Append 2)

n

0

4.01

Produces spines, thorns or burrs

n

0

4.02

Allelopathic

n

0

4.03

Parasitic

n

0

4.04

Unpalatable to grazing animals

n

-1

4.05

Toxic to animals

n

0

4.06

Host for recognized pests and pathogens

n

0

4.07

Causes allergies or is otherwise toxic to humans

n

0

4.08

Creates a fire hazard in natural ecosystems

n

0

4.09

Is a shade tolerant plant at some stage of its life cycle

n

0

4.1

Tolerates a wide range of soil conditions (or limestone conditions if not a volcanic island)

y

1

4.11

Climbing or smothering growth habit

4.12

Forms dense thickets

y

1

5.01

Aquatic

n

0

5.02

Grass

n

0

5.03

Nitrogen fixing woody plant

n

0

5.04

Geophyte (herbaceous with underground storage organs -- bulbs, corms, or tubers)

n

0

6.01

Evidence of substantial reproductive failure in native habitat

n

0

6.02

Produces viable seed.

y

1

6.03

Hybridizes naturally

y

1

6.04

Self-compatible or apomictic

y

1

6.05

Requires specialist pollinators

n

0

6.06

Reproduction by vegetative fragmentation

n

-1

6.07

Minimum generative time (years) 1 year = 1, 2 or 3 years = 0, 4+ years = -1

7.01

Propagules likely to be dispersed unintentionally (plants growing in heavily trafficked areas)

n

-1

7.02

Propagules dispersed intentionally by people

y

1

7.03

Propagules likely to disperse as a produce contaminant

n

-1

7.04

Propagules adapted to wind dispersal

y

1

7.05

Propagules water dispersed

n

-1

7.06

Propagules bird dispersed

n

-1

7.07

Propagules dispersed by other animals (externally)

n

-1

7.08

Propagules survive passage through the gut

n

-1

8.01

Prolific seed production (>1000/m2)

y

1

8.02

Evidence that a persistent propagule bank is formed (>1 yr)

n

-1

8.03

Well controlled by herbicides

8.04

Tolerates, or benefits from, mutilation, cultivation, or fire

y

1

8.05

Effective natural enemies present locally (e.g. introduced biocontrol agents)

Total score:

5

Notes

Reference

1.01

No evidence.

1.02

1.03

2.01

Native: AUSTRALASIA. New Zealand: New Zealand - North Island.

http://www.ars-grin.gov/cgi-bin/npgs/html/tax_search.pl

2.02

plant has naturalized north of New Zealand - range uncertain

2.03

(1)USDA zones 10-11 (2)"Hardiness: USDA Zone 10a: to -1.1° C (30° F), USDA Zone 10b: to 1.7° C (35° F), USDA Zone 11: above 4.5° C (40° F).

(1)http://florawww.eeb.uconn.edu/acc_num/200500008.html (2)http://davesgarden.com/pf/go/2243/index.html

2.04

"naturalized in South Africa & Victoria, Australia"

http://www.ars-grin.gov/cgi-bin/npgs/html/tax_search.pl

2.05

"they have naturalised in the Wellington area and in the north of the South Island. Pōhutukawa have been introduced to other countries with mild-to-warm climates, including south-eastern Australia; as well, they have naturalised on Norfolk Island. In coastal California, they are a popular street and lawn tree; San Francisco's Friends of the Urban Forest estimates that it is the third-most-commonly planted street tree in San Francisco over the last two decades.[citation needed] In parts of South Africa, the Pōhutukawa grows so well that it has become a nuisance, and is coming to be regarded as an invasive species."

http://en.wikipedia.org/wiki/Pohutukawa

3.01

"naturalized in South Africa & Victoria, Australia"

http://www.ars-grin.gov/cgi-bin/npgs/html/tax_search.pl

3.02

No evidence

3.03

No evidence

3.04

(1)Listed on the 'Declared weeds and invader plants: Category 3 plants' in Africa. [Declared Weeds & Alien Invader Plants are divided into three categories: Category 1 Plants. This is the strictest category. These plants may not occur on any land or inland water surface other than in a biological control reserve. Except for the purposes of establishing a biological control reserve, one may not plant, maintain, multiply or propagate such plants, import or sell or acquire propagating material of such plants except with the written exception of the executive officer.
Category 2 Plants. These are plants with a commercial application and may may only be grown in demarcated areas (or biological control reserves). See the Government Gazette listed below for details relating to demarcated areas. Other provisions of category 1 apply.
Category 3 Plants. The regulations regarding these plants are the same as for category 1, except that plants already in existence at the time of the commencement of these regulations are exempt, unless they occur within 30 metres of a 1:50 year flood line of river, stream etc.]
(2)"Although common in cultivation and even considered an invasive alien in parts of South Africa, the native populations of Pōhutukawa are in serious decline, primarily due to an alien species, the Australian brushtail possum." (3)"Pohutukawa (Metrosideros excelsa) has been planted as an ornamental in the Western Cape province of South Africa for many years and large mature trees can be seen in the gardens of Cape Town and other towns of the province where it is known locally as the New Zealand bottlebrush. In recent years the pohutukawa along with many other introduced invasive plants has begun to invade sections of the nearby fynbos, a delicate ecosystem of 71,000 square kilometres, renowned for its huge range of native plant species. The fine seed of the pohutukawa, which is produced in vast quantities, is spread by wind and some areas in the fynbos provide ideal conditions for germination and growth of the plant. The dense masses of seedlings that are developing and becoming established indicate the likelihood that impenetrable stands of trees that suppress native flora will develop. While no official programme to control the pohutukawa has been initiated as yet, concerned locals have already begun to remove the plants."

(1)http://www.plantzafrica.com/miscell/aliens4.htm (2)http://florawww.eeb.uconn.edu/acc_num/200500008.html (3)http://www.rnzih.org.nz/pages/NativeWeeds.htm

3.05

No evidence

4.01

No evidence

4.02

No evidence

4.03

No evidence

4.04

"Herbivory: Goats have been recognised as “the single most destructive herbivore” introduced to the islands of the world (King 1985). By eating young trees in a forest they prevent the replacement of adult trees that form the forest canopy.
Reduction in native biodiversity: Atkinson (1960) reported on the devastating effect that browsing goats had inflicted upon the vegetation of Cuvier Island. The forest was originally dominated by the New Zealand pohutukawa Metrosideros excelsa Gaertn. However the regeneration of this and other tree species has been completely stopped and on the seaward slopes there was little of this original woody vegetation left (Sykes 1969).
A 36-year study of forest recovery since the eradication of goats showed that more than two-thirds of the tree and shrub species present had been reduced by goats, some to very low numbers. At least six other plant species on the island had probably been eliminated by goats (Atkinson, in prep.). In addition, early collections indicate that at least six plant species became extinct on the island as a result of the goats."

http://www.issg.org/database/species/impact_info.asp?si=40&fr=1&sts=

4.05

No evidence

4.06

This site lists 34 fungi species to be associated with M. excelsa. [No evidence or recognized pests or pathogens].

http://nt.ars-grin.gov/fungaldatabases/new_allView.cfm?whichone=
FungusHost&thisName=Metrosideros%20excelsa
&organismtype=Host&fromallCount=yes

4.07

No evidence

4.08

Probably not (1) An evergreen tree - that usually grows solitary. (2) Metrosideros excelsa is on the list of 'Some fire retardant plants for the Blue Mountains'.

(1)http://www.smgrowers.com/products/plants/plantdisplay.asp?plant_id=1058 (2)http://www.bluemountains.org.au/BushLiving/LivingNearTheBush/fire.html

4.09

(1)Exposure - full sun. (2)"It cannot grow in the shade." (3)Sun Exposure: Full Sun

(1)http://www.smgrowers.com/products/plants/plantdisplay.asp?plant_id=1058 (3)http://davesgarden.com/pf/go/2243/index.html

4.1

(1)"Metrosideros excelsa is for the most part a coastal tree … It is very tolerant of coastal exposure, and also apparently of very acid conditions, as it is able to tolerate the acid soils and acid rains around the thermal lakes and springs of Rotorua." (2)"These trees will survive well in salt and sandy environments and can even grow with their roots in salt water, hence their Maori name Pohutukawa meaning 'sprinkled with spray." (3)"The plant prefers light (sandy), medium (loamy) and heavy (clay) soils and requires well-drained soil. The plant prefers acid, neutral and basic (alkaline) soils."

(1)http://www.ars-grin.gov/cgi-bin/npgs/html/tax_search.pl (2)http://www.abc.net.au/gardening/stories/s788278.htm (3)http://www.ibiblio.org/pfaf/cgi-bin/arr_html?Metrosideros+excelsa&CAN=COMIND

4.11

(1)"These trees behave like many of the tropical figs of northern Australia and elsewhere, growing as stranglers (stranglers are trees which germinate in the tops of other trees, sending aerial roots down to the ground where they take root and eventually envelop and "strangle" their host tree). " (2)"This reveals the fact that many in this genus are epiphytic and are similar to our Strangler Figs of northern rainforests, sometimes starting life as a seedling high up in another tree’s canopy and sending down aerial roots which after many years strangle the host tree."

(1)http://www.horticulture.unimelb.edu.au/potm/metroexc/plant.htm (2)http://www.global-garden.com.au/backissuez/0112feature1.htm

4.12

(1)" ...The fine seed of the pohutukawa, which is produced in vast quantities, is spread by wind and some areas in the fynbos provide ideal conditions for germination and growth of the plant. The dense masses of seedlings that are developing and becoming established indicate the likelihood that impenetrable stands of trees that suppress native flora will develop. While no official programme to control the pohutukawa has been initiated as yet, concerned locals have already begun to remove the plants." (2)"Project Crimson Trust works with mainland pohutukawa (Metrosideros excelsa) the large prolific coastal tree we all love. As the Trust does not advocate planting pohutukawa outside of its natural growing area (north of a line drawn from Gisborne to New Plymouth), it is therefore impossible for us to recommend taking the species to another country. A very good example to support this is the south-western tip of South Africa where pohutukawa has been listed as a serious alien invader due to stands of impenetrable pohutukawa growing there."

(1)http://www.rnzih.org.nz/pages/NativeWeeds.htm (2)https://www.projectcrimson.org.nz/faq/

5.01

A tree 20 to 30 ft tall.

http://www.smgrowers.com/products/plants/plantdisplay.asp?plant_id=1058

5.02

5.03

5.04

6.01

(1)"One of New Zealands most stunning and well known trees that is grown throughout the world. . Pohutukawa grow well in all soils and is surprisingly hardy but is a little frost tender while young.The plants generally flower at Christmas time, hence the common name "N.Z. Christmas Tree." (2)"Metrosideros excelsa Sol. ex Gaertn. (pohutukawa) is a distinctive, multistemmed tree of rocky coastlines endemic to New Zealand. Individual trees reach a height of 25 m and flower profusely for a peak time of ~ 2 wk in summer (November - January). "

American Journal of Botany 87 (9) : 1265-1271 July, 2000

6.02

Propagation from seed.

http://www.ibiblio.org/pfaf/cgi-bin/arr_html?Metrosideros+excelsa&CAN=COMIND

6.03

"Allen (1961; p 325) summarizes previous occurrences of natural hybrids between nothern rata and pohutukawa, isting "Rangitoto Island, Titirangi, Whau Creek (at New Lynn, Auckland) and Lake Taupo". Two Northland collections "which are very likely to be result of this cross" (B.H. Macmilland, pers com.) are CHR 159045 from Tameterau, Whangarei (E. K. Reynolds, 1965) and CHR 228748 from Tutukaka (W.R. Sykes 1972). One further specimen is known (CHR 321438) from Great Barrier Island (J.K.B.). This was found 400 m north of Motairehe Stream, north of Port Fitzroy. ..."

Ogle, C.C. and Bartlett, J.K. 1980. New Plant Records from Northland, New Zealand. New Zealand Journal of Botany. 18: 141-300.

6.04

"The results of this study show that contribution of the mating system of pohutukawa to the survival of the species in the wild. Overall, the reproductive strategy of the species could be labelled "wasteful but sufficient". The species is primarily a selfer, as mass-flowering allows a substantial amount of geitonogamous selfing. There is a large overall output of selfed seeds in each tree per season, although self-incompatability of individual trees may reduce this number consideratbly. Slelection eliminates a large portion of the selfed progeny from populations and ensures highly heterozygous adult populations. Furthermore, despite high rates of selfing, the absolute number of outcrossed seeds per tree is very large and sufficient to ensure the survival of the species."

Schmidt-Adam, Gabriele; Young, Andrew G.; Murray, Brian G. Low outcrossing rates and shift in pollinators in New Zealand pohutukawa (Metrosideros excelsa; Myrtaceae) American Journal of Botany 87 (9) : 1265-1271 July, 2000

6.05

"The flowers are hermaphrodite (have both male and female organs) and are pollinated by Bees."

http://www.ibiblio.org/pfaf/cgi-bin/arr_html?Metrosideros+excelsa&CAN=COMIND

6.06

No evidence of spread by vegetative means.

6.07

A large tree - but with high growth rate

Grotkopp, Eva, Rejmanek, Marcel High seedling relative growth rate and specific leaf area are traits of invasive species: phylogenetically independent contrasts of woody angiosperms
Am. J. Bot. 2007 94: 526-532

7.01

Probably not - no evidence of the species being planted in high traffic areas.

7.02

(1)The species has ornamental value. (2)"Metrosideros excelsa (New Zealand Bottlebrush or Christmas Tree) is a popular ornamental tree and hedge plant in coastal areas of the Western Cape."

(1)http://www.smgrowers.com/products/plants/plantdisplay.asp?plant_id=1058 (2)http://www.sabonet.org.za/aliens/aliens_part4_myrtaceae.htm

7.03

Probably not - no evidence of the species being grown in or around seed crop fields.

7.04

It produces large quantities of fine, wind-blown seed.

http://www.sabonet.org.za/aliens/aliens_part4_myrtaceae.htm

7.05

It produces large quantities of fine, wind-blown seed.

http://www.sabonet.org.za/aliens/aliens_part4_myrtaceae.htm

7.06

It produces large quantities of fine, wind-blown seed.

http://www.sabonet.org.za/aliens/aliens_part4_myrtaceae.htm

7.07

No evidence of the propagules having any means of attachment.

7.08

Probably not - no evidence of ingestion of fruits.

8.01

Probably yes - "Seed is very fine but particularly hardy."

http://www.bushmansfriend.co.nz/xurl/PageID/9165/ArticleID/-13996/function/moreinfo/content.html

8.02

Probably not - "Abstract: Mature seed capsules of pohutukawa (Metrosideros excelsa) contain a mixture of filled (embryo-containing) and unfilled (embryo-lacking) seeds. Both types of seeds were characterised with respect to their dimensions, weight, viability, and their germination rate under two different storage regimes. Filled seeds have a lower length/width ratio, and are approximately 25% heavier than unfilled seeds. Treatment of seeds with 1% tetrazolium chloride at 37degreeC resulted in staining of all filled, but no unfilled seeds. There was no difference in the numbers of filled seeds occupying the top, centre, and basal portions of capsules, and filled seeds were randomly disposed on the placenta. The germination rate of filled seeds was 99% upon harvesting and still exceeded 90% after one year of storage at +1degreeC. When stored at room temperature, this rate decreased to 58% after 6 months and there was no germination after one year of storage." 

Schmidt-Adam, Gabriele; Gould, Kevin S.; Murray, Brian G. Seed biology of Metrosideros excelsa (Myrtaceae). New Zealand Journal of Botany 40 (3) : 419-425 September 2002

8.03

The species is being controlled in South Africa fynbos but no evidence regarding the use of herbicides.

http://www.rnzih.org.nz/pages/NativeWeeds.htm

8.04

(2)"It is a hardy tree and will often regenerate after major damage "

(1)http://www.global-garden.com.au/backissuez/0112feature1.htm (2)http://www.opotiki.com/data/pohutuka.htm

8.05

Don’t know.