Flower petals and spent flower heads and stems are all ideal materials for composting. Flower petals are moist, nitrogen rich organic material that have a fine texture and will break down quickly. Flower petals and other moist, nitrogen-rich materials should be added to the compost pile in equal volume with dry, brown carbon-rich materials and a little bit of water to make the composting process work most efficiently.
Layer flower petals onto the top of an established compost pile creating an even layer not to exceed 2 inches in thickness. If you have more petals than that, alternate your layers of flower petals with dried brown carbon-rich material such as leaves, wood chips, coffee grounds, dried grass or shredded newsprint.
Sprinkle water over the top of the new material with a slowly running hose or watering can. Add just enough water to make the new layers lightly moist but not soaking wet.
Leave the pile undisturbed for three to five days. On the fourth or fifth day turn the compost pile thoroughly by moving the top layers into the center of the pile and moving what was in the center to the top and sides of the pile.
Add just a few more cups of water if the pile seems dry at the top after you turn it to ensure that the top of the pile is evenly and lightly moist.
Layer over more flower petals as they become available for composting and repeat the process.