How the Grass Changes.....

Picture

Seasons....

There are four seasons in Animal Crossing: winter, spring, summer, and autumn. Every season your grass will change to another color. The following image is of all four grass seasons/colors. On this sample picture above, you see 'square grass'.

Solutions to excessive grass loss.....

Some players find that after several weeks of play, there is very little grass left. In the winter, complete erosion of the grassy areas
(which is necessary to have snow cover) can prevent players from obtaining Snowman furniture. One drastic solution is to time travel forward using the Wii system clock, loading one day at a time. Simply jumping forward a few months has no effect on the grass. Your grass should be fully grown back from a complete desert in six months, although if the situation wasn't too bad, it'll take less time than that.
Picture
Another method is to place pattern paths to all the most visited places in town, and using them exclusively while the grass is in a state of recovery. Note that the patterns themselves do not have an effect on the grass in any way. They are merely a tool to help players develop paths only where they are desired. Early regrowth is fragile; walking over it even once will cause it to visibly disappear. For this reason, players who use this method may have to refrain from shaking trees or digging up fossils and gyroids until the grass reaches a certain stage of recovery. Grass grows faster under trees and flowers and, for a town that has not yet eroded to the point of desertification, planting trees and flowers in problem areas may be enough to reverse or halt the damage. However, the act of walking to the flowers to water them will erode the grass you walk across to reach the flowers. Placing the flowers along the pattern paths themselves is an option while the town is in the early stages of recovery. Natural dirt spots will eventually grow back, too.

Whether you're trying to prevent future desertification or are in the process of regrowing your grass, there are are a few things that should be avoided. Unnecessary reloading of the game makes your grass more vulnerable to new wear. Not reloading is not a complete solution, however, as the grass becomes susceptible to the wear again after 6 a.m.. When there are multiple players of the same game file, it may be difficult to avoid reloading. In those cases, pattern paths may be additionally beneficial, as they encourage different people to take the same routes through the town. You should only walk or run where you want a path to form.

Grass wear is actually affected by the current season. During winter (especially December), the grass will be at its worst, wearing away quickly. During spring and summer (especially June), the grass will wear down roughly half as fast.

Note that the grass in your town is arranged in invisible, pattern-sized blocks. When a block of grass is growing back from total dirt, you'll be able to see a small circle of grass, dead center in that block. More bits of grass will appear within the block as time goes on, or the grass will shrink away if it's walked on.