Probably a hybrid between C. sepium subsp. roseata and C. silvatica subsp. disjuncta (both present in reserve network). The leaves are too broad, the flower too large and too pale for C. sepium subsp. roseata (see http://naturewatch.org.nz/observations/2483936, http://naturewatch.org.nz/observations/2470612 and http://naturewatch.org.nz/observations/2643497 for subsp. roseata)
In mown berm to road
The two photos are of the three large patches found close to here.
Occasional amongst coastal grassland
Common on coastal sand
Common liane amongst dryland shrubland
Occasional on dryland banks