@serenesurface-- I've used valerian alone, as well as valerian and hops for sleep problems. In my experience, they work better together than alone. Valerian is great for creating drowsiness and makes me fall asleep. Hops is relaxing and seems to improve sleep quality. So when I use them together, I fall asleep on time and I stay asleep.
It's also convenient to use them together because they are available together in capsule form or in tea bags. So it's not like you have to measure them and mix them yourself.