Rough lemon tree

A very ancient species of lemon, native to the Himalayas.
Its cold hardiness is exceptional for a true lemon (non-hybrid).

The fruit is a deep yellow that turns orange when fully ripe.
It is medium-sized and irregularly shaped, with rough skin, and is harvested throughout the winter.
Its juice is particularly tart.

The tree is very vigorous and productive, thorny, and rather bushy.

References:
https://idtools.org/tools/1076/index.cfm?packageID=1179&entityID=8783