The symbolic ceremony was a forerunner to a larger Matariki Tu Rakau commemorative community tree planting project next month.
The project will involve the planting of 350,000 trees throughout New Zealand.
The Signal Hill planting was part of the commemoration of the 100th anniversary of World War One.
Otago Southland District RSA president Jenepher Glover-Shepherd said the young trees would be "living memorials" to past and present servicemen and women, and would complement existing and more traditional memorials.
The tree planting by the two ministers was "breaking ground" for a significant Matariki Tu Rakau event next month when 850 trees will be planted on Signal Hill.
During late August there will also be plantings at Waikouaiti and in the reserve near Goodwood.
The plantings are being carried out close to Matariki as it is the optimal time for planting.
The programme is to run for three years and may also take place in Northland.