Essentially we’re querying leaves getting knocked off on the backswing or downswing of your stroke here, for we’ve all played enough golf from terrible spots to know that after impact, when the ball has gone, the club can plough on through all sorts of undergrowth and foliage following our quest to extricate ourselves.
And we’re not talking about practice swings here, either, where the most ardent Rules police would have you locked up for knocking off even the tiniest of leaves. The reality is, it’s not quite like that as Rule 8.1a prohibits only doing anything that improves the conditions affecting the stroke.
Those conditions are clarified in the Definitions section of the Rules as follows: “The lie of the player’s ball at rest, the area of intended stance, the area of intended swing, the line of play and the relief area where the player will drop or place a ball.”
If the leaves you knock off on a practice swing improve the conditions affecting the stroke – i.e., improve the area of intended swing in this instance, making it easier for you to play unimpeded - you will be penalised two strokes in stroke play or loss of hole in match play. If they don’t, you won’t.
Obviously this may need a judgment call at times but hold fire before you dive in to tell your opponent you’re claiming the hole because you saw a small leaf fall to the ground on a practice swing as that will depend on whether or not the conditions affecting the stroke were improved.
But we digress as we’re talking about leaves getting knocked off during the actual stroke here rather than on a practice swing. To find the answer, we need to move on to Rule 8.1b, which talks about actions that are allowed without penalty in preparing for or making a stroke… even if doing so improves the conditions affecting the stroke.
The full Rules of Golf lists 11 scenarios here, and seventh on that list is “make a stroke or a backswing for a stroke that is then made”. In other words, there is no penalty for knocking leaves off on either backswing or downswing if you go on to make the stroke.
If you abort the stroke on clipping leaves or a branch and knocking something off, we would be back into the realms of that practice swing scenario here and would need to make a call as to whether or not those actions have improved the conditions affecting the stroke you go on to make at the next attempt. There is a chance that the answer will be yes if you were swinging down the line that the stroke requires, so the moral of the tale is, if you feel your club knock something off a bush or tree on your backswing or downswing, keep going and make the stroke!