I've got two blueberries (Polaris and Chippewa) in 4' x 4' raised beds and they're doing great. Right now, they're surrounded by a lot of pine needles, which I know is good for them but . . . they're in a prominent place and I'd like to make the ground around them more aesthetically pleasing (and healthy for them). Any suggestions for a compatible ground cover? I've read lingonberries or strawberries, but I wonder what might be best for an enclosed space. Thanks very much!