When teeing off I know that if you knock the ball off the tee then you can re-tee it, but what if you aren't using a tee and you do the same thing...ie. nudge the ball when addressing it on the teeing ground?

Same thing Peter, as long as the nudge does not move the ball in front of the tee markers, in which case it must be replaced behind them. You can even stop - move the ball into a better spot - whatever.The ball isn't in play until a stroke (or an attempt at a stroke) has been made from the teeing ground. Nudging, therefore, as part of addressing a ball that is not in play will not incur a penalty but once a stroke is played at the ball, it is deemed in play - even if only knocked off a tee peg. It must then be played as it lies, when even nudges (that move the ball) are counted.

And Peter, if you play again from the tee because your drive went out of bounds you are allowed to tee up again, BUT your new ball is in play so if you knock it off the tee you incur a penalty.

Niblick - Every time a ball is put into play from the teeing ground it's the same thing. No penalty if the ball is moved before the stroke.

Ouch. How did I get that wrong? I know I use these threads to test out my knowledge and will therefore be wrong from time to time, but it is mortifying when it happens!

So that includes deciding your drive is unplayable and going back to the tee to play your next shot?

Yep:11-3/3  Original Ball Out of Bounds; Ball Played Under Stroke-and-Distance Procedure Falls Off Tee at AddressQ. A player played his original ball out of bounds from the teeing ground. Under Rule 27-1, he teed up another ball. When addressing the ball, he touched it and it fell off the tee. What is the ruling?A. There is no penalty, because a teed ball is not in play until a stroke has been made at it (see Definition of "Ball in Play"). The ball may be re-teed (Rule 11-3).

I think what I may have been thinking of and allowing myself to be confused by is the situation where a player on the tee has an air shot: his ball is therefore in play and if he knocks the ball off the tee while addressing it for his 2nd shot, it is a penalty? Hope I'm right this time.

Phew!

And to my embarrassment, I have to admit to an airshot a year or so ago. Was very very careful addressing the ball the second time

Niblick - nothing to be embarraessed about. The problem with airshots are people NOT admitting them and claiming it was a practice swing ...But you can always tell. A player almost loosing his balance and looking like Goofy afterwards has not made a practice swing!

I don't know if I looked like Goofy, but the real give away was that the follow through of my practice swing doesn't include sweary words

On a related subject I have been informed that if you dislodge leaves from overhanging branches on the teeing ground with your practise swing you are considered to have "improved your lie" and hence incur a penalty - even though the ball is not actually in play.Is this true and just how stupid is it if it is?

I can see why you can't decide where to tee up, spot an overhanging branch and break it off then tee off from that point. Or if you have addressed the ball and break something with the backswing and stop the swing - I see that as well as you have, in my opinion, put the ball in play.But take the instance where you place a ball on the on one side of the tee box. You know there are branches that MIGHT interfere so take a practice swing and down comes a few leaves. You then move your ball - it's not in play remember -  a few feet over and hey presto you are good to go. in this instance you MIGHT (number of leaves etc) have incurred a penalty. Daft in my opinion.If the ball isn't in play how can you have a lie to improve?

Imagine your thought process:"ok, so i've got to tee the ball up in the teeing area-  oh sh**, there are some branches there..  I always hit a massive slice to i like to tee it up on the right of the teebox... grr, if only i could break off that branch, i could tee up exactly where i want to....  well i know i can't, but there is only a little bit of that branch overhanging, just a couple of leaves... i'll tee up over there- it'll be a squeeze but if i get the right angle i'll be alright.... ok ball is teed up i'll take a practice swi.. oh shite, i'm right in those leaves. That was a bit daft. I might have knocked the worst of them out of the way, but i'm not sure.... Ok, i'd better move the ball across a bit so i CAN get a swing at it.." i can understand the rule

I can't understand a tee with overhanging branches that would interfere with your swing in the first place!

Shouldn't happen but it does. The player will just have to tee his ball somewhere else and complain in the clubhouse afterwards.

That's remarkable and doesn't say much for the course manager where it happens.