I have a line of about eleven very tall, mature hemlocks along my driveway in New York. There is a ten foot "hole" where one is missing right in the middle which I would like to plug, preferably with something other than hemlock, a friendly, fast-growiing buddy to them. Also, is it possible to plant under them? They are well established and cared for, about three feet apart but their branches are high now, beginning about 6 feet from the ground. I need to screen under them, have only about 3 feet in front but decent sun.Thanks