For most golfers in the United States, holing a putt requires you to do three things: accurately judge how hard you need to hit the ball, gauge how much the ball will curve as it rolls, and make a stroke that gets the ball rolling on your intended line with the ideal speed. But golfers in Florida and other hot-weather climates often need to factor in a fourth element: grain. If you watch this week’s Cognizant Classic at the Palm Beaches or any of the other Florida Swing events on television, you’re going to hear a lot about it.

Grain refers to the direction in which the grass on the putting surface grows. It is not uniform, so at venues like the Championship Course at PGA National Resort & Spa, site of this week’s Cognizant Classic at the Palm Beaches, you will see dark areas and silver-toned regions on the greens.

The grain can have a subtle but meaningful effect on how balls roll, and as Daniel Berger, a native Floridian, said on Wednesday, it has to be dealt with.

“I think just being a Florida guy, subconsciously, you pick up on things that probably the average person wouldn't pick up on,” he said. “The coloring of the greens, does it look shiny, does it look dark, what side of the cup is burned out. Those are things that just growing up as a teenager you get used to, but they make a huge difference.”

Bentgrass greens tend to grow evenly and produce a uniform putting surface. Uphill putts take away speed and downhill putts roll quicker on bentgrass, but even on smooth Bermuda greens, the grain can add or reduce speed, which in turn can magnify or reduce the effect of breaks.

“If you have a left-to-right putt, but with right-to-left grain, it's clearly not going to break as much,” Berger said. “It's a bit of a skill to decide how much break you're going to play based on how the grain is going, but I think it's an advantage. It's a reason why I've probably played well here (in Florida) in the past, because other guys aren't quite as used to it.”

When a player is standing behind a ball and facing the hole, dark regions on the green indicate that the grass is growing towards the golfer, so they are putting into the grain and the putt will be slowed. If the putting surface is shiny, the grass is growing away from the player and the same putt will be faster.

“I think you just pick up on the nuances,” Berger said. “When you look at a 20-footer and you see it's shiny, you know that it's downgrain, you know it's going to be quicker. Obviously, the other side of it would be you see it's dark, it's not as shiny, it's going to be slower, but interestingly, early on in my career, I never really thought about it that much. I just kind of putted. And then, as I've gotten older, I've started to play more grain and I think it's been helpful for me. It definitely is a factor. It's a major factor.”

This article originally appeared on Golfweek: What is grain in golf and why does it make putting hard?