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 Dōbutsu no Mori e+ and earlier, flowers cannot breed or wilt. All sorts of colors can be bought from Tom Nook without the need to hybridize. The Blue Cosmos is exclusive to Dōbutsu no Mori, Dōbutsu no Mori +, Animal Crossing and Dōbutsu no Mori e+ and was not available anymore in Animal Crossing: Wild World and later. Also, they cannot be picked up in Dōbutsu no Mori, Dōbutsu no Mori + or Animal Crossing unlike in later games, so they cannot be sold or worn. In Dōbutsu no Mori e+, flowers can be picked, but it will result in the flower being destroyed and the player will be holding the flower in their hands after being picked, then if the inventory is opened up and attempting to grab it from the player will result in the flower disappearing from their hands and cannot be placed in the inventory.
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. Each day, there is a 80% chance for each non-watered flower to wilt at 6a.m., 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. Watering flowers that have not wilted yet prevents the flower from wilting the next day. To prevent any flowers from wilting, players should water every single flower in their town. Unless the player save and quit while it's raining or snowing, which hydrates all the flowers in the town, preventing wilting the next day at 6am, if it has been raining or snowing during the day and the player save and quit while it's on an hour when it's not raining or snowing, the flowers will still wilt the next day at 6am (unless the player has watered all the flowers). Players must make sure they save and quit when it's still raining or snowing in that hour. If players are trying to water every flower in the town, chances are that there are flowers that they will miss each day (unless they save and quit while it's raining or snowing), which can result in those flowers wilting the next day at 6am. To prevent this from happening, the best method is to water the flowers while walking up to the edge (or river) in the north and then move across a square (or three), then walking down while watering the flowers until the player reaches the edge at the cliff (or river) in the south, then moving across a square (or three) again and walking up while watering again and so on. Which is in a snake-like pattern to ensure that every flower is watered. The best way to water more flowers in Animal Crossing: New Leaf while walking up and down is with the golden can, it also saves the player time and effort since it can water nine squares in front the player, also players can move three squares when reaching the edge at the north or south instead of one. This wilting process applies to all flowers except the golden rose, dandelion and dandelion puffs.
In Animal Crossing: New Leaf, flowers grows in groups of four, unlike in previous games where they grow in groups of three. 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.
 Flowers in Dōbutsu no Mori e+ and earlier
 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. However the Blue Cosmos cannot be obtained by any means, even through breeding in Wild World or later, due to the fact that it only exists in Dōbutsu no Mori e+ and earlier.
 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