Answer: Dry shade is always a challenge, especially when it is under maple trees with their dense canopy and greedy roots. Even with a top dressing of compost, the soil will continue to be dry and nutrient poor due to the tree roots. The roots will grow upward through the top dressing, so it gives only a limited window for your groundcover to become established.
You will need to dig a planting hole clear of the fine feeder roots for each new plant and also keep them watered while they become established. Mulching in between them with an organic mulch until they fill in will help a little bit with the moisture issue, and also help feed the soil as it breaks down over time.
You might be able to grow the old standby evergreen groundcovers of English ivy or Vinca minor there; in my experience Epimedium is among the most tolerant of dry shade conditions. The drawback is that it is not an evergreen. Hosta is also deciduous. Hosta really grows better in a rich soil that is evenly moist yet well drained. It looks good combined with epimedium, so perhaps you could experiment a bit and see which one seems to grow better, then increase the proportion of that plant.
Another option is to use up some of the space under the trees for a seating area with perhaps a small table, chairs, a fountain and some large planters filled with colorful annuals. This provides visual interest without relying on plants in the ground.
You might also want to consult with your local county extension and/or professional nursery staff to see if they have suggestions. Best of luck with your project!
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