Grass

&nbsp Grass is what covers your town (in the areas not govered by buildings, pavement, and dirt). In early December, snow falls and replaces all of your town's grass. On December 25th, the snow melts, and the grass comes back.

Grass throughout the Animal Crossing series
Animal Crossing: Population Growing:

In this game, all of the town not occupied by pavement or buildings was filled up with grass. There were only a few spots occupied by dirt, and those were designed in figure 8-like shapes.

Animal Crossing: Wild World:

In this game, more of the land was occupied by dirt rather than grass, giving player's towns a more "desert" like feel.

Animal Crossing: City Folk:

In the latest installment of the series, the player starts out with an almost complete town of grass. However, as the player progresses, the grass starts to disappear. This process is called Grass Deterioration. The player's town goes from looking like a Population Growing town to a town that looks more like a Wild World town.

Grass designs
There are six different designs for snow/grass in the Animal Crossing series. The patterns change when grass turns to snow and vice-versa. The patterns are as shown:

Pattern 1:

Grass: Square pattern

Snow: Circle/octagon pattern

Pattern 2:

Grass: Triangle pattern

Snow: Square pattern

Pattern 3:

Grass: Circle pattern

Snow: Star pattern (the snow equivalent of the triangle grass pattern)