Maples that have roots near the surface are a special challenge. When we have long periods without rain we see plants under large shade trees suffering because the trees monopolize most of the available moisture and nutrients.
It is helpful to shred the leaves in the fall to use as a mulch to improve the soil systematically over time. As well, incorporating organic matter into each hole we dig when we are planting is a good ongoing practice.
The selection of perennial ground cover plants such as hosta, epimedium, cranesbill geranium, lily-of-the-valley, lamium, pulmonaria, sweet woodruff, ferns and lady's mantle is also a good practice.
Wildflowers such as trillium and Virginia bluebells usually enjoy sheltered sites under trees also.
Remember to water any new plants consistently the first season after they are planted, as this is essential for them to become established and thrive with the competition they will encounter from the tree roots.
Also remember to water in times of drought. A teaspoon of slow release granular fertilizer in each planting hole when new plants are introduced is also essential to provide nutrients over the first crucial three months following the installation.
Fill in the bare spots the first few years with annuals such as impatiens to provide blocks of color. Also plant plenty of tiny spring bulbs. They bloom before the deciduous trees leaf out each spring so even bulbs that need sunshine will thrive.