Pupils at Bishop Perowne C of E College planted trees as part of Cllr Karen Lewing's and Bob Whitelaw, the chair of the Arboretum Residents Association, Branch Out Campaign.
The campaign, which received funding from the Tree Council, aims to provide new woodland and fruit trees in Lansdowne Park.
Cllr Lewing said: "I was motivated to plant more trees in the park when I saw small children playing and a mum with sunburn and realized that the play area had no shade.
"I also wanted the park to have more interest – I know how important our green spaces are to local residents."