Cough with hot phlegm according to Chinese Medicine

The two Chinese Medicinal herbs most likely to help treat cough with hot phlegm

Why might Blackberry Lily Rhizome (She Gan) help with cough with hot phlegm?

Because it is a herb specifically indicated to treat cough with hot phlegm as can be seen on Blackberry Lily Rhizome's page.

Blackberry Lily Rhizomes is a Cold herb that tastes Bitter. It targets the Lung.

Its main actions are: Clears Heat. Detoxifies Fire poison especially for sore throat. Resolves Phlegm and lowers Lung Qi

Read more about Blackberry Lily Rhizomes here

Why might Catechu (Er Cha) help with cough with hot phlegm?

Because it is a herb specifically indicated to treat cough with hot phlegm as can be seen on Catechu's page.

Catechu is a Neutral herb that tastes Bitter and Pungent. It targets the Heart and the Lung.

Its main actions are: Clear Phlegm. Clears Heat and drains Dampness. Applied externally for stopping bleeding.

Read more about Catechu here