Animal Crossing: Wild World/Flower breeding
Flower breeding is the act of pairing flowers of the same species together in order to create new colour flowers from them. This can happen any day after you put two flowers together, and can happen whether you intended it to or not.
Normally, your town will produce 3-5 flowers in the wild. These wild flowers can either be new flowers that grow in your town or 'child' flowers that grow from existing flowers in your town.
 How to breed
When creating hybrids you need 2 flowers of the same species. This means you cannot cross a tulip with a rose or a pansy with a cosmos. Some mixtures of colours do not produce child flowers at all so you have to be sure that the flowers you are cross breeding have the potential to create hybrids.
 Hybrid pairing table
When cross breeding flowers there is always the possibility that the child flower will be the same colour as one (or both) of the parents. Cross breeding can take time to produce new interesting coloured flowers.
Using this table you can successfully cross all applicable flowers to maximize you hybrid crop.
Gold roses are not bred this way. You obtain Gold roses by watering a withering black rose with the golden watering can.
Blue and Gold Roses are very rare but can be sold for 2,500 bells at Nook's.
 Flower arrangement
To ensure that flowers will cross breed you must arrange them so that they are ‘touching’. For the flowers to be touching each other this means they have to be positioned alongside each other, up and down or diagonally. The empty spaces around the two flowers are the spots where child flowers will potentially grow. Planting diagonally appears to produce more opportunity for hybrids to grow. It is important to have free spaces around the flowers or hybrids will not be produced.
Be sure to check around your neighbours houses. Hybrids can happen at any time and any place within your town so you may find them growing round other houses too. Black and gold flowers are extremely rare.