Kingdom:   Plantae
(Unranked):        Angiosperms
(Unranked):        Eudicots
(Unranked):        Core eudicots
Order:    Saxifragales
Family:    Haloragaceae
Genus:        Haloragis
Species:       Haloragis erecta
Binomial name: Haloragis erecta subsp. erecta
Synonyms: Cercodia erecta, Haloragis colensoi
Common name: Shrubby haloragi, Erect Seaberry,  Fireweed, Toatoa (a name also given to celery pine, Phyllocladus glaucous), Fireweed. 

Haloragis erecta subsp. erecta is a plant herb species that is endemic to New Zealand: Kermadec, North, South, Stewart and Chatham Islands. It is found up to an altitude of 500m and grows on the edges or forest clearings, on cliffs, banks, roadsides, unkempt gardens and wasteland within urban areas.
It has coarsely toothed opposite leaves up to 3 cm long and they have teeth up to 4 mm long.
Stems are square and reddish in colour. The red or pink flowers are insignificant and appear throughout the year. Haloragis erecta is often confused as a weed.
It is easily grown from seeds or cuttings. Seeds from the plant were taken to England as early as 1778 and were grown in KewGardens. 
A subspecies is Haloragis erecta subsp. cartilanginea (Surville Cliffs haloragis) is endemic to a 120 ha exposure of serpentinised peridotite rocks at the Surville Cliffs, North Cape. It has small round leaves and is sold as a cascading pot plant.  

For more details visit:  http://www.nzpcn.org.nz/flora_details.aspx?ID=1966  

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Haloragis erecta ssp. erecta growing roadside north of Hawera, South Taranaki
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The underside of a young leaf.
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Young stems
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A mature 4-angled stem
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Haloragis Erecta Rubra ‘Wellington Bronze’ which also known as ‘Erect Seaberry’ is a cultivar sold in nurseries. It has saw-toothed leaves which are various shades of bronze and purple. It develops spikes of insignificant greenish-yellow flowers.
Photographed at Te Kainga Marire Gardens, Spencer Place, New Plymouth.
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The underside of a new leaf,
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Thanks to Wikipedia for text and information http://creativecommons.org/licenses/by-sa/3.0/