An excerpt from an article "Questions you've always wanted to ask about polo" by Alex Webbe - Click for full article 

Question 1. Why do the players wear white pants?

Like many polo traditions, this one can be traced back to India, where the game was played by nobility and later introduced to British army officers stationed there in the nineteenth century.  Competing in the intense heat, players preferred clothing that was light in weight and color.

We all know that jodhpurs, the tailored riding britches still worn by some players, took their name from the Indian state of Jodhpur, but how many also realize that Brooks Brothers developed the button-down collar specifically for polo players (who wanted to keep their collar tabs from flapping in their faces)?  Polo, it seems, has always been fashionable.

Question 2. What happened to the horses’ manes and tails?

Free flowing manes and tails are a danger in polo because they can become entangled with players’ mallets or with the reins as the rider tries to control his horse.  Manes, therefore, are shaved and the ponies’ tails are wrapped or braided to prevent the hazard.  Wrapping or braiding long ago supplanted the crueler practice of docking (amputating) the horse’s tail near the base so all that remained was a short stump.

Question 3. Can you use the same horse for an entire game?

No.  Polo ponies run the equivalent of one to two miles during a seven-and-a-half-minute chukker, so they must be rested frequently.  At the high-goal level, players ideally will have a fresh horse every period although many will “double” on their best ponies.  Even at this level, it’s rare but not unheard of for a pony to be played three chukkers in the same game—it happened in the famed International Matches between England and the United States.

Question 4. What is a score called and why do the teams change directions whenever there is one?

Points scored in polo are called goals, which is much more straightforward than trying to explain why polo teams don’t change field directions by periods or halves like other sports.  One theory is that the practice of changing after every point (sorry, goal) scored originated in the days when many polo fields ran east-west (they’re usually situated north-south now) and neither team wanted to play for extended periods of time with the sun and/or wind in their faces.  It’s a plausible explanation, especially when you consider that in late nineteenth-century periods of play changed every time a goal was scored.  We know the practice dates to at least 1873, when England’s Hurlingham Polo Association drew up its polo rules.

Question 5. What are all the people doing out on the field at halftime?

It’s customary at polo matches to invite the public onto the field at halftime to tread in the divots kicked up by the horses.  The custom has a practical as well as a public-relations value: the field is repaired for the teams by the time they begin the second half of play.  It’s not clear who was the first enterprising club manager to realize he had an abundant and cheap grounds-keeping crew at his disposal, but old-timers will tell you the job used to be done by hired help.  In the 1920s, for example, laborers at the polo clubs tapped in the divots after every period with a tool resembling an oversized croquet mallet.  Between games, wives of the polo grooms, many of whom were immigrants, could be found on hands and knees cutting dandelions and other weeds from the field.

Question 6. What do they call the opening play in polo?

In hockey, it’s a face-off, in basketball it’s the tip-in, but in polo it’s known as the throw-in.  The umpire tosses the ball in between the two teams as they line up parallel to one another.  In earlier days, the custom was to place the ball in the middle of the field and have two opposing players charge it from opposite directions.  This practice was eventually discontinued, probably because of incidents like the one that occurred in 1888 at Myopia Polo Club in Massachusetts.  Living up to the club’s name, the riders charged myopically at the ball and collided head-on, knocking one of them out cold.

Question 7. Why are there no left-handed players?

Lefties were officially banned from polo in the mid-1930s for safety reasons, but the restriction was relaxed after World War II when polo players of any persuasion were a scarce lot.  The USPA reinstated the lefty ban again in 1974 and it’s stuck: there are no more left-handed polo players.  To understand why, consider this:  you’re driving merrily down the road when all of a sudden, coming straight at you, is a crazed Englishman driving on the left side of the road.  The panic you’d feel in that situation is just what a right-handed polo player feels when he and a lefty approach the ball from opposite directions.

Are women allowed to play polo with men?

Since both sexes are rated on the same handicap scale, men and women can and do play together.  The highest rated woman player in the world is rated at 3 goals (America’s Sunny Hale).  Sixty-odd years ago, the U. S. Women’s Polo Association had a 10-goal woman player.