Q.Do I Have To Clean Up All The Spent Oriental Lilly Petals From Garden Floor ?
I have over 50 plants is various parts of a huge garden approximately 700sq feet
Certified GKH Gardening Expert
Not at all! This would be a good litter to leave around to help enrich your soil as it breaks down and won't harm anything unless they are falling from disease. In this case, they will need to be removed to avoid re-spreading disease.
However, most people clean spent blooms by cutting them before they fall off. This is, simply, to maintain a cleaner appearance.
These article will explain how MOST gardeners choose to care for them:
https://www.gardeningknowhow.com/ornamental/bulbs/lily/deadheading-lily-plants.htm