Exactly when the Chinese market gardens started up at Chinaman's Hill isn't known -- but they were in full operation by at least the mid 1880s. They became a cause of concern for letter writers to the NZ Herald when questions were raised as the the purity of the Western Springs water supply:

"I think the general public will be surprised to learn that -- barring a very low estimate from the number of loads that pass through Newton -- ten tons daily, or over three thousand tons yearly, of stable manure, besides a great quantity of urine, is deposited in the Chinese gardens, within a quarter of a mile of and in the direct line of drainage to the springs from which our water is pumped ..."


("Aqua Pura", NZ Herald 26 February 1887)


Thomas Wong Doo, the patriarch of the successful Wong Doo family, is said to have joined older brothers on the market gardens at Chinaman's Hill, sometime during the 1880s. (Information from his obituary, NZ Herald, 21 November 1858) Kaaren Hiyama identified some more names:

"Tranliteration and the reversal of Chinese name order makes connections difficult. In the 1890s valuation rolls show a Fong Chaw living in one of Thomas Faulder's houses on the southern side of Surrey Crescent opposite Billington's block, and possibly working that land. Thomas Billington's property, between Stanmore and Old Mill Roads and Francis Street, was leased from 1884 to four Fong brothers and in 1890 a Quong Fong Ming, gardener, is listed as the occupier of the house and land belonging to Billington ... Memories of elderly local people of the market gardeners hawking their produce in horse and cart are the only remaining evidence of large-scale cultivation which continued for decades, supplementing home-grown vegetables." (pp. 28-29)

http://timespanner.blogspot.com/2009/09/chinamans-hill-grey-lynn.html