Citrus halimii
Citrus halimii B.C.Stone

Citrus halimii, known as mountain citron, is a citrus species with sour fruit. It was first described in 1973 by B.C. Stone and is native to regions including Borneo, Malaya, and Thailand. Initially classified among the papedas, it is now recognized as a wild species closely related to kumquats, and not to the true citron.
Description
Citrus halimii is a member of the Rutaceae family and the Citrus genus. It is characterized by its sour fruit and is found in the BR, Borneo, Malaya, and Thailand. Originally grouped with the papedas, further research has shown it to be a wild citrus species with a close relationship to kumquats. It is distinct from the true citron and was first documented in 1973.
Distribution
BR · Borneo · Malaya · Thailand
