Strictly speaking the terms shrub and bush are interchangeable. But being raised by an Englishman who liked gardening the term shrub for me has come to mean a small growing tree that has in some way been shaped and formed to have a manicured look about it. Whereas, a bush would, as the term suggests, be an unkempt shrub growing in a natural wild state and unfettered by mans intervention. Man interferes with the growth of bushes as a mechanism of control mainly for the following reasons: shade control, aesthetics, productivity, and encroachment. These things are very necessary, as who in their right mind would want a tree to block the morning sun from bathing their conservatory with warmth.