The Australian Desert Lime - Citrus glauca, is native to outback Queensland, New South Wales and South Australia. It produces small citrus fruit that turn bright yellow and have a tart flavour. The fruit can be eaten whole rind and all.
The tree is fairly small with thin leaves that are a bluish green colour.
The fruit and tree are actually quite attractive, I found this specimen growing at the Waite Arboretum, Adelaide.
The tree have some pretty nasty spikes on it, especially on the lower branches. This is apparently an adaptation against being eaten by Kangaroos and the spikes largely disappear on the higher branches.
The desert lime has been brought into cultivation in a small scale and I have seen plants for sale at local hardware stores.