Posted: 18/08/2017 at 10:48
I definitely would advise against that, they will grow on quicker if you buy smaller ones and pinch out the tops.
a lot of people make the mistake of thinking buying big will give an instant hedge, it won't, because they will be tall and thin, you need to aim for short and bushy, then let them grow up, they will soon reach 6' if you plant them right.
Someone on here did the very same thing, he wasn't happy with them as they looked sparse, we recommend that he cut them down by half, he did, and has a beautiful hedge now, and that was only about two or three years ago.
if you wait until winter you can get bare root ones, about 3tall, they are much cheaper and will grow on well, making roots through the winter then shoot up in the Spring.
Pick out the tops whenever you walk past them, all helps to thicken from the bottom.