If The Greensward is not the correct book, you may be thinking of one of these similar "Green" themed titles:
by Susan Wiggs: A story of survival and redemption based on real-life "Magdalene Laundries". Download The Greensward Girl epub
The story follows Silas and Pitch, the "Lady's Horsemen," as they investigate a tortured spirit in Devon. The narrative explores themes of forbidden magic, necromancy, and the evolving attraction between a human and a daemon. If The Greensward is not the correct book,
Historical Fantasy with elements of mystery and romance. the "Lady's Horsemen
The Silent Rifleman! A tale of the Texan prairies - Project Gutenberg
It is the fourth book in The Diabolus Chronicles (Pitch & Sickle series).