How to Replace a separate mesh

I have made a tree with the sapling Addon. I want my leaves to be replace with the icosphere. I want to make the grapes bunch. Is there any way to replace the leaves to icosphere.
tree icosphere.blend (1.8 MB)

I tried with object Data but i have to select manually single leaves and object data. I want to replace all the leaves to icosphere. Any suggestion or help. Thanks


Have you tried using link data: ctrl-l