"a plant or plant part or an extract or mixture of these used to prevent, alleviate, or cure disease—called also herbal, herbal medicine"
http://www.merriam-webster.com/medical/herbal remedy

In UK, in general speech and conversation, and also commercially, this term is the most commonly used out of all the expressions which describe the herbs and plants used in herbal medicine.
Examples of usage are as follows:

"Herbal remedy: A medication prepared from plants, including most of the world's traditional remedies for disease. Most people think of herbal remedies as products sold over the counter as "supplements", such as saw palmetto extract or goldenseal ointment. However, many over- the-counter and prescription drugs are based on ingredients originally derived from plants, including aspirin and digoxin. Lab tests have shown that some herbal remedies are indeed effective against illness..."
http://www.medterms.com/script/main/art.asp?articlekey=11464


"Thousands of years ago, there were no doctors. Our ancestors fell sick and many died. As time went by, they discovered that their surroundings provided ways and means to recover from sickness. Herbal Remedies & natural medicine became popular. Whether it was .... Some scientist and doctors now agree that herbal remedies can be useful in many treatments."
http://www.herbalremedy.org/