No they will be fertile. However, they will most likely need pollination - tui, bellbird, waxeye etc will usually do this but it depends on their density in your area, other nectar sources AND the clone you have. The original stock was cutting grown from the sole wild plant and that material had larger flowers with the stamens set well away from the stigma - it rarely sets seed - but seedlings raised from the seed that was have over several generations produced smaller flowers with the stamens and stigma set more closely together - they readily set seed, whether visited by birds or not. If you get no seed set, trying hand pollinating the flowers, or be patient and wait a few more years, in time it will flower more heavily and birds will find it.