This tree was already mature when we bought the property more than 20 years ago so I estimate that it's more than 30 years old.
The tree itself is not much to look at for most of the year, until the winter. This probably explains why I've not given it the attention it needs over the years. I don't like using chemicals and sprays if I can help it but this year I decided to spray all my fruit trees with copper as some were showing signs of disease including this orange.
Several years ago when I decided to landscape this area I had to hack into its roots quite severely to put the steps in, which caused it to suffer a bit, but I think it's bounced back now.
Izumi uses the oranges quite a bit in salads as shown in my post about Florence Fennel
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Update October 2018.
Last year the orange tree didn't produce many flowers and hardly any fruit. So, I decided it was time to give it some attention and look after it properly. So I gave it a generous feed of granular citrus food which I spread around the drip line in the Autumn and another spray of copper over the winter which I haven't done for a few years. I did the same thing to a few other citrus and fruiting trees in the garden while I was about it.
The results have been very encouraging! The tree is now covered in flowers and looking much healthier than it was, which bodes well for next seasons crop of oranges. As a bonus the orange tree in recent weeks has played host to regular visits from the NZ native Tui, who come to feed on the nectar.
Come to think of it, I’ve seen more Tuis in the garden this year than I can remember for a while. I must be doing something right.