If you want to reduce the number of rows because you want to limit the number of characters then you may take a look at http://contactform7.com/max-min-length-options-and-character-count/
is this possible to target and override through CSS?
You may use CSS to control the style/looks of the textarea in terms of width, height, etc. But limiting the actual number of lines of entry in the textarea can generally be done via JavaScript.
