As a matter fact, it comes from two different species – Phellodron chinense Schneld. (Chuan Huang Bai) and Phelloendron amurense Rupr. (Guan Huang Bai). The former mainly grows in Sichuan, Hubei, Guizhou, Yunnan, Jiangxi, Zhejiang and other provinces in China. And the latter is produced mainly from the Northeast and North China, such as provinces of Heilongjiang, Liaoning, Jilin, and Hebei.

WHAT'S FRIED PHELLODENDRI CORTEX USED FOR? 
TCM wise, this herb is bitter and cold in nature. It goes to two channels like kidney and urinary bladder. Its major functions include clearing heat, drying dampness, purging pathogenic fire, putting out steaming heat, detoxicating, and curing furuncles. Besides, the salted one is good at nourishing Yin to decrease internal heat. And main uses and indications are dysentery due to dampness-heat, jaundice, abnormal vaginal discharge, heat stranguria, athlete's foot, atrophy and flaccidity, hectic fever, consumptive fever, night sweat, Nocturnal Emission, sores, Eczema, and itching. Common dosage is from 3 to 12 grams.

Phellodendron

FORMS OF FRIED AMUR CORK TREE BARK 
It's important to be clear here that it refers to more than one type due to different fried initiators involved. To cater to different therapeutical needs, more often than not it needs to tweak the nature of the herb to the benefit of specific patient. So does the Phellodendron Amurense bark. And it also comes in three common variations – the salt-fried, the wine-fried and the charred. And their main differences are as follows.

1) The unprocessed
The unprocessed is bitter, dry, cold, and heavy in nature. Then it has better functions in clearing heat-fire and dispelling dampness.

2) The salt-fried
The salt-fried mitigates the innate bitter, dry nature. At the same time it enhances the effects of nourishing yin for lowering fire and clearing asthenic fever.

3) The wine-fried
The wine-fried reduces the inherent bitter, cold property. The purposes of such practice are twofold – prevent from injuring the Spleen Yang and induce the pharmaceutical effect upward and then clear upper-Jiao heat by virtue of the rising tendency of wine.

4) The charred
The charred is mainly used for eliminating dampness-heat. And because it is somewhat astringent, it is often employed to treat blood in the stool and metrorrhagia.