NZ prisons might be better than US's but that's not saying much.
It's just gardens in general which are illegal (without a license, obviously) https://www.reddit.com/r/newzealand/comments/2nem47/can_you_...
If limes (or anything else, like grass, or strawberries, or potatoes, or mint, ...) happen to grow on your property it's fine and you can collect them, but if you tend to them or there's evidence you planted them it's gardening, and the penalties can be steep.
And police don't look kindly on non-native tasty edibles[0] which "just happen" to grow on the properties of unlicensed owners, as often as not the owner is assumed at fault and fined (though of course the harshest penalties like prison require positive evidence of guilt).
[0] and NZ has very few native or pre-european plant edibles at all, let alone tasty ones: https://teara.govt.nz/en/1966/plants-edible-native
It's just gardens in general which are illegal
[1] http://knowyourmeme.com/memes/new-zealand-gardening-law-hoax [2] http://www.huffingtonpost.co.uk/entry/new-zealand-gardening-...
Whereas I'm reasonably convinced you're a joyless shitpail[0] who manages to "well, actually"[1] a joke.
I know NZ can be resource limited for a couple of reasons, but I'm trying to imagine why growing things would present enough danger to warrant the law being involved.
I have no idea why, but limes are extortionately expensive in New Zealand, even for imported goods.
They're currently NZ$35 per kg (over US$10 per lb).
It's standard to get a slice of lemon in your Corona (which are also extortionately expensive in NZ)