Today I planted two 'Ruby' Loropetalum- 3 gallon size and gold mound spirea's. The loropetalum is in front of a tea olive. Since the 'Ruby' is a dwarf and small right now, what would you suggest as an annual or perrennial that can be planted in-between the loropetalum and tea olive to give a filled in look until the loropetalum gets more mature?