By planting certain combinations of flowers next to each other (vertically, horizontally, or diagonally), you may spawn hybrid flowers. In Animal Crossing New Leaf, it gets a bit tougher with a new color introduced to the Tulips, and a few diferent combinations in the Pansies and Roses. Lillies and Violets are new flowers introduced in this series and also have thier own set of Hybrids. Obtain Gold Roses by watering withering Black Roses with the Golden Can. Gold Roses never wither, though they can disappear if trampled. Flowers, including hybrids, can spawn their parents. For example, Orange Cosmos next to Orange Cosmos can spawn Orange Cosmos, P-Red Cosmos, or P-Yellow Cosmos. Flowers, including hybrids, can act like their parents when breeding. For example, two Red Roses can spawn Pink Roses if at least one of the Red Roses spawned from a pairing of P-Red Roses and P-White Roses. Spreading Fertilizer on flowers will increase the probability of producing hybrid flowers. Spawnings significantly increase on days following precipitation. You can also increase spawnings by watering healthy flowers.

Here is the list of required combinations:

Pink Tulips = Red Tulips + White Tulips
Orange Tulips = Red Tulips + Yellow Tulips
Black Tulips = Red Tulips + Red Tulips
Purple Tulips = Orange Tulips + Orange Tulips

Pink Cosmos = Red Cosmos + White Cosmos
Orange Cosmos = Red Cosmos + Yellow Cosmos
Black Cosmos = Orange Cosmos + Orange Cosmos

Orange Pansies = Red Pansies + Yellow Pansies
Blue Pansies = White Pansies + White Pansies
Red Pansies* = Blue Pansies + Red Pansies
Purple Pansies = Red Pansies* + Red Pansies*
(It seems that you need Red Pansies that have spawned from Blue Pansies in
order to spawn Purple Pansies.)
Orange Pansies* = Blue Pansies + Orange Pansies
Purple Pansies = Orange Pansies* + Orange Pansies*
(It also seems that you need Orange Pansies that have spawned from Blue Pansies
in order to spawn Purple Pansies.)

Pink Roses = Red Roses + White Roses
Orange Roses = Red Roses + Yellow Roses
Purple Roses = White Roses + White Roses
Black Roses = Red Roses + Red Roses
Red Roses* = Orange Roses + Purple Roses
Blue Roses = Red Roses* + Red Roses*
(It seems that you need Red Roses that have spawned from Orange Roses and
Purple Roses in order to spawn Blue Roses.)

Pink Lilies = Red Lilies + White Lilies
Orange Lilies = Red Lilies + Yellow Lilies
Black Lilies = Red Lilies + Red Lilies

Blue Violets = Purple Violets + White Violets

White Carnations = Red Carnations + Pink Carnations