The best ground cover to use under a Japanese maple is one that is both attractive and beneficial for the tree. Creeping phlox, liriope, and Ajuga are all great choices as they thrive in partial shade and provide color throughout the seasons. These plants also require little maintenance and help keep weeds away from your tree’s roots. Another option would be mulch or wood chips which can help retain moisture in soil while preventing weed growth. Whichever you choose, make sure it won’t compete with your tree for nutrients by avoiding deep-rooted plants such as grasses or shrubs near its base.