From Nookipedia, the Animal Crossing wiki
Flowers in the Animal Crossing series are small clusters of brightly colored flowers that live throughout all four seasons. They can be bought from Tom Nook's Store or Leif's Garden Shop, are grown by villagers, and grow randomly around the town. In Animal Crossing, flowers cannot breed or wilt. All sorts of colors can be bought from Tom Nook without the need to hybridize. Also, they cannot be picked up like in later games, so they cannot be sold or worn.
In later games, flowers, unless they are wilted, can be picked up as with any item. They can also be displayed in the player's house or, since Animal Crossing: City Folk, be worn on the player's hair. A flower worn this way will take the place of a hat. The rose, however, it is held between the teeth and will take the place of an accessory or helmet.
Flowers can be destroyed in some ways. If the player runs on a bunch many times, the flowers will be destroyed. If the player attempts to pick up a wilted flower, the player plucks it instead, removing it. The player can also use a shovel to dig where the flower is, destroying it.
There are four common types of flowers: roses, cosmos, tulips, and pansies. Various combinations of flowers can be bred to form new colors, such as the yellow and red pansies, which create an orange pansy. Flowers wilt periodically, turning a brown color. They can be revived by being watered with a watering can on the same day that they wilt, and will return to normal the following day. This wilting process applies to all flowers but the golden rose, which is created after watering a wilted black rose with a golden watering can.
In Animal Crossing: New Leaf, flowers grows in groups of four, unlike in previous games where they grow in groups of threes. New flowers, such as lilies and violets, are also present in this game. The ability to wear flowers in the hair of a player, which was introduced in City Folk, also reappears, again taking the place of a hat. Hybridization remains a feature for flowers.
 Special flowers
Hybrids can be obtained from Wild World onwards. In Animal Crossing, hybrids can be bought from Tom Nook's, but cannot be bred.
 How to Hybridize
If two different specimen of the same species are planted next to each other, on the next morning, there is a chance they will interact and create a new flower in one of the spaces next to either of the parents. For example, red tulips and white tulips can produce pink tulips. There are a few guidelines to follow to do this.
Even if the hybridization conditions are met, there is no guarantee it will occur. Only three to five new flowers appear in a town in a day, and most hybridization pairings can produce a non-hybrid child, so it may take a while for any particular hybridization to occur. There are a few things may increase the chance of hybridization.
Once a hybrid is produced, it can reproduce quickly by crossing it with any other flower. Not all flowers can create hybrids, however.
 Hybridization chart