Well, by 'streams full of stars' the poet is referring to the stars that are reflected in the streams. The poem leisure talks about all the cares that we have in life and which don't let us find the time to appreciate the beauty of nature all around us. It is not a very symbolic poem and can be interpreted on the surface, since it does not have a deeper underlying meaning. So while describing the beauties of nature when the poet says ' stream full of stars', he means the reflection of stars in a stream on a starry night, which is a breathtaking sight.
