Answer: It is very difficult to establish any planting to compete successfully with mature maple roots for light, water and nutrients. Hosta would have been my suggestion because it is well able to tolerate shade and is relatively undemanding in terms of nutrients. Hosta is usually able to compete once it has become established.
You might try again, carefully digging individual holes with ample space for the hosta roots, then watering them generously for the entire season after planting so as to encourage them to become very well rooted and healthy. The following season you could probably back off on the watering somewhat, and by the third year you woudl only need to water during dry spells. Using a layer of organic mulch several inches thick would also help with keeping the soil evenly moist. It also continures feeding the soil slowly as it breaks down over time. Finally, when you water, wait a few hours and then dig down to see how far your watering actually went, it can be surprising. Make sure you are watering deep enough to encourage deep rooting and not just dampening the shallow surface.
Keep in mind too that hostas tend to sit the first year then grow bigger the next, then really take off in about the third year. Some varieties are slower growing than others, too, so that could make a difference. Often the less expensive medium sized plain green types or the very common variegated form are faster growers and more vigorous than the more elaborate (and more expensive) plants.
If you truly feel you gave the hosta a fighting chance, then you might want to reconsider your plans and look at other options such as a gravel treatment combined with a large planter tub filled with colorful annuals or some other out of ground solution to covering and decorating the area. Good luck with your shade area.
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