Young plants grow faster than older plants. In a very fertile environment with good moisture and plenty of room, young plants grow at around 30cm per year and the older ones at around 10cm with 2mm on the girth.
Pohutukawa can grow to 20m high with a 35m crown.
In the natural coastal environment you see trees that are literally hundreds of years old. It is also common to see large species cultivated in some home gardens, which would be 100 years old.