That chart lists the flower types that, when cross-pollinated, will produce the Citrus flower. Most of those flowers are rare, exotic species that are only available by purchasing exotic seeds or getting lucky with mutation.

The difficulty with trying to create a Ball Cactus by breeding or mutation is that you have to be very far along in the game, have plenty of money, and be a bit lucky. Exotic seeds are expensive and require the best soil. Mutation is expensive, also, and the random element to the results can make getting exactly what you want difficult.