In Chinese culture, we believe every foods has either Ying or Yang attribute. Ying mean heat and Yang mean cool.  Notice the symbol of the Ying and Yang is equal; one NEVER over power the other.  90% of most foods have Ying attribute and 10% are Yang; so you can see the imbalance.  Most greens are Yang and chrysanthemum tea are know for thousand of years in China as Yang.