Combine dates, cherries, and citron, if desired, in a large mixing bowl; add 1 cup flour, stirring to coat well. Add walnuts, stirring well; set aside.
Combine soda and water, stirring well; set aside.
Cream butter in a large mixing bowl; gradually add sugar, beating well. Add eggs, one at a time, beating well after each addition.
Sift together remaining flour, baking powder, and salt in a medium mixing bowl. Add to creamed mixture; stir well. Add dissolved soda and vanilla, stirring well. Stir in reserved fruit mixture.
Drop dough by heaping teaspoonfuls 2 inches apart onto greased cookie sheets. Bake at 275° for 30 minutes or until lightly browned. Remove from cookie sheets, and cool on wire racks. Store in airtight containers.