When you observe and evaluate a golf green that you’re going to play, it's vital to study the break and the grain of the course. On extremely grainy greens reading a putt can be twice as hard. The grain on the grass can reduce the length of a 3 foot putt up to four or five inches. Remember, the break is the amount a putt moves from right to left, or left to right, on a green. The grass of the course can affect the ball’s break. The grain of grass refers to when grass grows in a particular direction. This is why observing the grain and taking it's direction into account is so important.
When playing greens with a lot of grain remember that the grain of the grass will follow the sun. If you are uncertain as to which way a putt will break on grainy greens look into the sky and wherever the sun is know that the putt will be influenced in that direction.
The slope, topographical features such as water and mountains, the grain of the grass, and (perhaps most important) how hard you hit the ball, will dictate the break.
Look for the natural slope of the terrain:
Once you know the lowest point, look at each green in detail. If you’re on an older course, because of drainage the greens probably slope from back to front. Greens nowadays have more humps and undulations than ever and are surrounded by more bunkers. And the sand tells a tale: Most courses are designed so that water runs past a bunker and not into it. Take that insight into account when you line up a putt.
Putts downgrain (in the same direction the grass is growing) will go faster than putts into the grain (in the opposite direction from the grass growth). The grain of a course will have an effect on where you have to aim a putt.
Examine the cup to find out which way the grass is growing. You may see a ragged half and a smooth, or sharp, half on the lip of the cup — that shows the direction in which the grass is growing. The ragged look is caused by the grass’s tendency to grow and fray. If you can’t tell either way, go to the fringe (the edge of the green). The grass on the fringe is longer, so you can usually see the direction of the grain right away.
Generally speaking, an architect will try to use the thinnest possible blade when dealing with grasses, and, given the climate, he/she will try to get that grass to grow straight up to eliminate grain.
