Sentence:  Ontario 's foliage is most vivid from about Sept. 23 to Oct. 10 , with both Muskoka ( 100 miles north of Toronto ) and Haliburton ( 125 miles northwest of Toronto ) holding color cavalcades <WSD>starting</WSD> Sept. 23 . 
Meaning of the word marked with <WSD> tags:  take the first step or steps in carrying out an action