Depending upon whether the area where the hedges have been planted is the Common Property of the Strata Plan or part of the Lot/s (Unit) such as 'garden space”, the following By-Laws apply under the provisions of the (NSW) Strata Schemes Management Act 1996:
4. Damage to lawns, etc on common property
An owner or occupier must not damage any lawn, garden, tree, shrub, plant or flower on the common property. You must not use any part of common property as your own garden.
17. Appearance of the lot
Unless an owner or occupier has the written permission of the owners corporation, they must not keep anything within their lot that is not in keeping with the appearance of the rest of the building. This does not apply to the hanging of any washing, towelling, bedding, clothing, or other articles mentioned in By-law 10.
Hope this assists.