Under-planting maple trees in the landscape can create a lush and finished look to a garden. Under-planting can also increase the planting acreage making use of otherwise dull or lost space. As most maple species are large trees, under-planting species should be chosen for complementary characteristics such a shade tolerance, preference for moist and acidic soil as well as to complement and contrast the appearance of the tree.
Choose a palette of perennial plants hardy in your area so that there will be minimal disruption to the soil under the maple tree once the initial plantings have been established. Forgo tender perennials and annuals that require constant lifting from the soil and transplanting.
Select a mix of plants that complement and contrast with one another harmoniously considering color, height, spread, texture, leaf shape, hue and growth habit such as mounding or trailing. Choose what you like using these elements to create interest.
Clear the surface of the soil of any weeds, fallen branches, cuttings, leaves or other debris. Lay down 6-inches of compost and well aged manure or good quality garden soil around the root zone of the tree. Keep the soil a few inches form the trunk and spread out in a formal circle or more informal shape with sweeping natural curves, according to your preference.
Lay out the plants while in the pot to create your composition. Put tall plants near to the trunk and repeat the placement of the same plant in three or more areas to make a random repeat that will create a unified look and visual interest. When happy with the placement and composition, pick up your trowel and spade to plant.
Dig holes to accommodate the root ball of each plant in its chosen location. Dig through the topdressing of compost and manure into the soil below, mixing the two soils together. Space the holes far enough apart to allow plenty of room for each plant to spread out to it mature size. Place the holes randomly or in a rhythm but not in straight rows. Make it look as though it is a natural occurrence.
Place each plant in the hole and firm the soil around the roots. Water in the plants lightly as you work so that none of them feel drought stress. Work your way around the tree, planting each plant and firming the soil around the roots.
Water the entire area in well until the top 6 inches of soil are drenched and collapse around the roots of the plant like a wet blanket. Monitor the soil moisture regularly, particularly in the few weeks after planting to prevent drought from occurring.