While tree roots certainly can be frustrating to gardeners, they are hardly insurmountable impediments to a lush and flowering landscape. In fact, beds below a sheltering tree can be some of the best areas for partial-sun plants. There are also several perennials with pretty hearty root systems that don't have any trouble muscling into root-infested territory.
One of the reasons annuals can work well among tree roots is that their own root systems tend to be shallow. By adding soil and compost over bothersome roots, flowers such as petunias can thrive--if they are planted in the proper soil type and fed and watered regularly. Enriching the soil with organic matter and working it down to a depth of 8 to 10 inches, even among tree roots, can help petunias "catch." However, a more important factor than tree roots may be shade. Petunias only work well under trees if they get plenty of sunshine.
Another annual often found near tree roots is impatiens. Building up the soil over the trees roots gives impatiens sufficient room for their relatively shallow roots. And grow they will. Impatiens, who love dappled sunlight, add huge splashes of color beneath trees. Considered shade plants, impatiens still require sunlight for full blossom growth. They are easy to grow, but need plenty of water and food.
Lily of the Valley
You probably will inhale the sweet smell of the perennial lily of the valley before you see its tiny white blossom. Once established in shaded, well-drained soil, lilies of the valley are prolific growers. Their strong and spreading root systems have no trouble twisting and turning around small and large roots. Thinning them in the spring keeps them from overtaking a garden.
The common daylily comes in a variety of colors and sizes and thrives in many soil types and conditions. Once established, it grows with little to no care, even proving hearty in drought-prone areas. Its long, fibrous root systems compete well against other strong root systems. Daylilies are often found growing wild among a variety of trees and bushes.
Chinese Lantern Plant
Another perennial that has no trouble thriving in a variety of gardens is the bright orange, fall-blooming Chinese lantern plant. Once established, the plant, which is also known as a jack o'lantern, spreads horizontally in a garden. Left to their own devices, they not only grow well among roots, but they can also quickly take over a garden.