Cedar trees, scrub oak trees, tall ragweed, goldenrod, tall native grasses, deadfalls, brushpiles....all of it can be utilized. The best natural ground blind hunts I've ever had have been impromptu deals on public land where I knew deer were passing through and I simply found some cover near their travel route. For instance in situations where I'm in tall native grasses or ragweed or goldenrod or some combination I'll get downwind of the trail maybe ten yards and stomp down a 4 foot diameter circle to sit in...then I stomp down a shoulder width lane toward where I expect deer to come from and at about a 45 degree angle to that lane I stomp down another lane to shoot through....works great....deer walk past the first lane and by the time they make it to the second lane I'm ready to shoot and they're at a perfect quartering away angle. DEAD DEER!!!!
Really as long as you sit still, have some cover and play the wind you'll be amazed how easy it is to get close to deer. The big key is getting in position for the shot and drawing without getting caught on ground level at close range. I like to let the deer walk past me before I try to shoot....I set myself up so that my bow is naturally pointed toward my shooting lane so I have to move as little as possible.
FUN!!!!!!