I assume this is the US Eng meaning of yard- what I'd call a garden? In my version of English, a yard is a bare, enclosed place used for storing stuff- probably with few plants, if any, and probably not somewhere you'd want to invite people to come and sit.
Yes, "piha" can be both a yard and a garden, but we also call a garden "puutarha". "Puutarha", I think, is more garden-y, while "piha" can also be more bare. Gardening is "puutarhanhoito": literally taking care of garden.