What will grow well among tree roots ...
We built a simi-circular brick planter that stands alone in the front yard. It was planted with miniature roses, Sweet alyssum (the alyssum smells so sweet!) and various other small plants that did wonderfully well.
After a few years they began to decline in spite of good care, plenty of water, compost, etc. In digging around them I found a mass of tree roots from the Cedar elm tree we planted about 15 feet away. There is no way to keep the tree roots out. Besides I love the tree. It grows tall rather than spreading so does not cast too much shade.
The roses were removed, and I tried a few other things there such as Shubby pink skullcap and Blue plumbago. The skullcap looked good for awhile, but needs full all day hot sun to do its best and this spot does not provide it, but the plumbago, which stays in continual bloom all summer, has spread itself and taken over the spot. Black foot daisies are planted along the edges and spill over.
I am so impressed that the plumbago is able to grow and bloom so well with minimal water among the tree roots that I wanted to tell you all about it.
What have y'all found that will grow among thick tree roots?