If you break a block under sunflower, peony, lilac or rose bush (double tall flower) it will drop 2 of that flower.
And if somebody wants to try and can't make it with that heres a step-by-step how-to:

1. place a double tall flower (peony, lilac, sunflower or rose bush)
2. break the block under the flower
3. you have duped the flower