I grow it without amending or protection in Portland. It is sold all over the place here. There are some great examples of it edging paths in the Chinese Garden here too.

That's encouraging. Thanks for the info.

I'd agree that you will have no problem growing either Ophiopogon or Liriope in a maritime western Washington climate. They are both extremely common here and require no particular specific care other than not allowing them to dry out excessively in our dry summers. In fact, one of the largest and best growers of black mondo grass in the area is located in northern Oregon and I bring in hundreds of plants from them each spring for my nursery.