In the height of New Zealand's summer season I spent 2 weeks working with Alpine Honey Co so I could learn and see the entire process of manuka honey production. Thousands of tons of Manuka honey is exported all over the world each year, with just over 1,500 tons coming into the UK and onto our super market shelves.
The kiwis are incredible marketers and with the manuka plant gracing every mountainous area across the north island and various parts of the south island the plant grows wildly just like our heather in Scotland. It has a very distinctive strong taste and texture, unlike most other honeys, being quite dense, and you only need to lift off a hive roof slightly to smell it.
The North Island only produce Manuka Honey so a vast amount which is exported will come only from there with a big percentage going straight to Asia for the use of "natural medicine". Manuka is extracted exactly the same as other honeys, but the purer it is - the higher price you will get for it, so it is usually extracted completely separately to other honeys. Manuka is harvested throughout the mid summer months in New Zealand which is January - February time.
Mixing Manuka honey with another type of honey would not be something the kiwis would do, due to as soon as it is mixed with something else, it brings the manuka pollen count down, the UMF of the Manuka down and the price down substantially.
How the UMF is graded is - the higher the UMF the better and more it will be worth. It is a bit of "luck of the drawer" in how high it is, but the Kiwi's theory is "the longer it sits in a container, the higher the UMF goes up, as it sets better over time a bit like ageing wine.
There is a similar plant of the same family called the Kanuka which is said to be a variation of Manuka, looks very similar, tastes very similar but does not have the UMF label that maunka has.
Overall the Manuka Honey is a billion dollar industry for the New Zealanders - and I think they would be a lot worse off without it. I personally haven't seen any scientific proof that it is that much better for you than your regular honey, but I do have proof that the kiwi's sure do know how to market a product and sell it successfully.