First, a funny story.
A guy I know was obsessed with hitting the ball "in to out." This guy would eventually develop a very good golf swing, but at the time this story takes place, he was shooting in the 90s and was just getting started on learning about the golf swing. At this point, though, the guy absolutely loved seeing his divots point to the right, because that was proof positive that the path was "in to out."
So I play nine holes with this guy, and my brother-in-law is along (I was actually subbing for his regular partner in a league). The first hole is a short par four with water, and I bunt a 5I into the fairway. My brother-in-law steps up with his 4I or something, takes his waggles, and then hits the ground 18 inches behind the ball, taking a big divot, and flat out missing the ball (how the divot missed the ball too I don't know).
The guy immediately says - in all seriousness - "Aha! I can tell you are a very good player because your divot is in to out!" :-) We still chuckle over that to this day...
Anyway, I'd like to thank Dr_Fu_Manchu for suggesting I write about divots: what they mean, what they can tell us, how big or small they should be, etc. It's a big topic, so I doubt I'll cover all of the topics here, but I think we might get to the bulk of them in the resulting discussion. So here goes...
Your divot - the actual piece of dislodged grass - should almost always fly to the left. The clubface closes (even if it's staying relatively square to the arc and closing slowly) and the path of the clubhead goes left, so most divots end up going to the left. Unlike the ball flight laws, divots tend to fly in the direction of the path of the clubhead at the end of the swing. ;-)
But if you want to talk about the hole in the dirt - frankly, I don't know what that's called, so I'll call it the "trench" unless I come up with something better in a few minutes - then that will rarely point to the right except in the rarest of cases (i.e. hooks). There are a few reasons for this, some involving the physics of how a golf club interacts with dirt and grass and your natural swing shape, but let's consider a stock push-draw with a 6-iron. If the player hits down on his six iron 6 degrees, his path will be roughly three or four degrees to the right (and his clubface, if he hits a good shot, will be about 1-2 degrees right of target). The ball is gone, the divot is taken, and the clubhead continues moving in three dimensions - down, out, and forward - to low point about four inches in front of the ball. Then it exits, with the clubhead moving again in three dimensions - forward (duh), up, and in.
In the end, we get a section of a circle - an arc, with roughly equal halves on each side of the low point. Because the total divot length is about six to eight inches, and because the angles will go from about 3 degrees to the right to three degrees to the left, the divot will "point" pretty straight. Have a look at the image to the right - that divot is "pretty straight" and that's with a sudden change in angle, not the smooth arc and rough edges you'd get from a normal fairway divot.
Review my "A-B-C-D-Plane" video for more on this, by the way, but consider the fact that you can hit a dead push as well - clubface and path both 3 degrees right, for example - and have a divot pointing relatively "straight" and also left of where the ball went.
Now, people who cut the ball, their divots most definitely point to the left because, if they're hitting down on the ball enough, they have to shift their baseline far enough left to counter the fact that the clubhead is still traveling down, out, and forward.
Long story short: drawers tend to have relatively straight divots, and faders tend to have divots pointing a fair amount to the left.
If you're a fan of looking at all of your divots, stop. Look at them generally, but unless you notice a pattern that persists, it's pointless. An individual divot can look "toe deep" or "heel deep" because the ground was different levels of softness or not quite level or a few other reasons. Don't obsess over individual divots.
If you see a pattern that's heel deep or toe deep, though, consider having your lie angles adjusted.
Lie Angles and Their Effects on Shot Direction (Click to show)
A brief aside.
You'll often hear it said that a "heel deep" divot (from having lie angles too upright) cause the ball to go left because "the heel catches the ground and it shuts the clubface down." You hear the opposite for a toe-deep divot: the toe digs into the ground first, opens the face, and causes the ball to go to the right.
That's not the case at all. If your lie angles are too upright, the clubface POINTS TO THE LEFT and if your lie angle is too flat, your clubface POINTS TO THE RIGHT. You don't take a divot until after the ball is gone - so how could the club "digging in" affect anything? Consider a sidehill lie: when the ball is above your feet, the clubface is pointing more to the left. It's the same thing if you have heel deep divots because your clubs are too upright.
The club digging in has nothing to do with the shot direction unless you hit the ball fat all the time.
Though I value tools like Trackman, oftentimes the people who promote Trackman the heaviest get a bit too wound up in them. They'll say that you can't properly diagnose a golfer based on ball flight and video alone. My response to that? You rarely fix a slice by telling the golfer to increase his angle of attack. That's another D-Plane thing, if you're interested...
Anyway, I'll explain what a good divot depth is by explaining the extremes. On one side, you've got the "pickers" of the golf ball. I used to be a picker. I also used to lose the flying wedge and have a shaft very close to vertical at impact. Picking the ball consistently is difficult, particularly with shorter clubs. On the other end you've got the really big diggers. These people have a lot of shaft lean at impact, because the club is still traveling down quite a bit before it gets out of the ground. As you can imagine, it's easier to take bigger divots with your wedge than your 4I, but I've seen some big divots taken with every club. Including my high school teammate Franco taking them with his driver. :-P
The proper divot depth varies by the conditions (wet, firm), the lie (uphill, downhill), the type of shot you want to play, and so on. Let's assume average conditions for all of them and a relatively stock shot. In this case, with a 6-iron, the divot should get through the fairway grass and expose dirt. It'll be the "one piece" type of divot that's on the edge of falling apart (again, given relatively average conditions - and they may vary in your area, because Bermuda divots tend to fall apart more easily in my experience - I'm talking about moist but not wet poa/bent/bluegrass divots). With a wedge the divot will want to stay together a bit more with more dirt, and with a long iron will be mostly grass with the bottom of the club just reaching the dirt. Why? Again, you have more shaft lean with wedges than you do with long irons. With a fairway metal or hybrid? Scuff marks will suffice.
If you play the ball back, you'll tend to take bigger divots than a guy who plays the ball forward. Duh. Right?
Flip and Divot
Can you flip and still take a divot? Though the real answer is "no" it really depends on you defining "flip" the same way I do as well as one other thing. You can flip (i.e. let's say a "flip" occurs if the shaft has passed the left arm prior to impact) yet still drive the clubhead down into the ground if your shoulder alignments and tilts are out of whack. You can also flip and still take a divot with the ball position well back. Think about it.
So no, a divot doesn't mean that you didn't flip.
I'll wrap things up there. I've got a video from Playing Lessons with the Pros that I need to put together. :-)
As always, please, discuss. If I'm wrong, show me how I am. If you have questions or something to add, write it up. Share this with your friends, too. The more discussion we get, the better the end result and the more we all learn.