Flowers of mulberry are minute and are borne in a catkin-like cluster. All the fruitlets developed from a flower cluster combined into a multiple fruit. The fruits ripen to white, pink, red or purple. The plants are cultivated for their edible fruits and for ornamental purpose. Mulberry leaves are also the only known food source for silkworms.

In the aspects of traditional chinese medicine, mulberry fruits belong to "Tonic herbs for Yin Deficiency" category. They could "nourish the kidneys and liver or moisten the lungs and stomach".

What makes mulberry fruits so special to be the only food source of silkworms?

References : https://www.britannica.com/plant/mulberry-plant
https://www.meandqi.com/herb-database/mulberry-fruits