Trees are often the most prominent feature in yard and can block sunlight received by large areas beneath them which can create an unsuitable environment for many plants. Barren areas of dirt or mulch around trees make for unsatisfying landscaping; while certain plants need direct sunlight to thrive, there are others that can do well living under trees.
Ground cover is a term used to describe small plants that spread quickly over the surface of ground, creating a thick lush look. Ground cover plants tend to be hardy, and can often survive in places that lack much direct sunlight. Examples of ground cover plants are English ivy, snow on the mountain, pachysandra,and ajuga. An advantage of using ground cover plants beneath a tree is that since they tend to remain relatively small, their root systems will not compete with large trees that have deeper roots. Another advantage is that you only have to plant a few different clumps of ground cover and it will spread around bare ground on its own over the course of several years. Ground cover plants also tend to be fairly low maintenance. One problem with using ground cover plants is that they can be tenacious and invasive, which means they can potentially invade other plant beds if they are allowed to spread too much.
Many woody shrub plants can do well underneath the branches of trees, which can create a fuller look than using shorter ground cover plants. Shrubs that do well in partial sunlight or shade include yews, boxwoods, hydrangeas, rhododendrons and azaleas. Shrubs will likely have somewhat deeper roots than short ground cover plants, which may disturb trees that are not as tough. Shrubs take some effort to maintain as new growth needs to be trimmed back to keep them from growing too large, and regular watering may be necessary for certain kinds of shrubs. Shrubs like yews and boxwood can be shaped through trimming which can make for a very tidy look.
Other Plants and Considerations
Certain types of flowers do well in shade and can be planted in beds under trees. Flowers that can do well in partial or full shade include impatiens, lily-of-the-valley, hosta and phlox. Ferns also tend to grow well in shade and can be found scattering the floors of many forests that have thick canopies. Whatever plants you choose to use under trees in your yard, it is most important to think about the health of the tree first. Don't plant large shrubs or bushes under trees that might be disturbed, and take care to avoid harming the tree's roots when you are planting. It is best to plant small young plants under trees to allow their roots to spread naturally without disturbing the tree.