Harry, if you look up the word "native", you'll find it is synonomous with
the work "indigenous". In the fields of zoology and botony this
means "originating". Thus, corn (maize) in not native to Africa, even
though it's been there hundreds of years. Corn in "native" to the Americas.
Ceonothus is "native" to California, proteas are "native" to South Africa,
even though they are both grown around the world. This is generally
understood when writing about things agricultural.