In large part because British wanted oriental goods and Chinese didn't want anything from Europe. Demanded silver for goods. Soon flow of silver going into China. British wanted it back. In 1839 Chinese said no more and confiscated stocks.
Second conflict ca.
10 years later. Cannabaceae- Hemp Family. Includes marijuana and hops. Many common names - reflects long intimate association. There are 1-3 species, depending upon which taxonomist you believe.