The adhesive force of wetting liquids specially water is responsible for capillary action, the capillary action is not possible for Mercury.

Capillary action is bad if you want to keep two liquids separate. Capillary action is difficult to control in terms of flow rate.

The narrower the bore of the tube ,the greater is the capillary action.

For example :A sponge retains water (on being dipped in water)is due to capillary action.

Capillary action will pull water up the stem to the flower and into the petals.

The adhesive intermolecular forces between the substance rising (the one experiencing capillary action) and the container (typically a capillary).