The school and the environment centre worked together to develop the garden, while the council provided the land, the plants and piles of mulch.
Balmacewen principal Andrew Hunter said 11 teachers spent time during the school holidays planting the reserve.
"We looked at this as a project we could adopt," Mr Hunter said.
The school used the reserve as part of its teaching programme, with pupils having monitored a stream as part of projects they had done, as well as learning about different plant species.
Environment Centre co-ordinator Hendrik Koch said 250 plants had been bought from the council's biodiversity fund.
The environment centre has managed the reserve land beside the Kaikorai Stream since 1996, to demonstrate sustainable gardening practices and grow plants using organic methods.
It received $5000 in the latest council biodiversity funding round, in which 11 people or organisations received a total of $34,000.
