Tree roots can be so thirsty they create the ground beneath and near their canopy inhospitable for several plants. 1 way to conserve moisture is using groundcovers. When landscaping around trees, look for flowering perennials that adapt well to dry soil and partial to full shade. Avoiding annuals is wise, since planting them year after year disturbs tree roots. Companion plantings also may depend on whether some of the trees chemically inhibit other plant development.
Protection of Tree Roots
When planting under or near trees, you need to lessen the magnitude of planting holes and the number of times that you plant to avoid damaging tree roots using shovels or other sharp tools. Most tree roots are in the initial 6 to 24 inches of soil and extend past the conclusion of a pit canopy, or drip line. Woody permanent origins, which you may often see above ground, anchor the tree. In contrast, trees receive much of their moisture and nutrients from short term, hair-like, feeder roots that are close to the soil’s surface and can easily be disturbed by repeated planting of annuals. As a result, it is better to plant perennials near trees. Selecting perennials in pots using diameters no bigger than about 4 ins keeps planting holes small. Eventually, perennial and tree roots effortlessly intermingle.
1 serious landscaping mistake that flower gardeners occasionally make is to produce raised planting areas around trees. It is possible to stunt a tree and finally kill it by placing extra soil on top of the ground through which its origins spread. A raised bed of only 4 inches of soil over part of a tree’s root zone badly decreases water and oxygen to roots. If you want to produce a ring of flowering plants around, and a few feet beyond, the drip line of a tree, a better choice is to mass one or two low-maintenance flowering perennials. Possible choices include heath aster (Symphyotrichum ericoides) and creeping phlox (Phlox subulata), which grow well in U.S. Department of Agriculture plant hardiness zones 9 and 10. They bear some shade, but require at least six hours of sunlight each day.
Whereas turf grasses often compete with trees for moisture and may slow the growth of young trees, flowering groundcovers that are drought and shade tolerant are beneficial under and around trees, since they preserve moisture. Two good choices for part-to-full shade are California Dutchman’s pipevine (Aristolochia californica) and Heuchera species, which are generally called coral bells or alumroot. Both work well in part-to-full shade. California Dutchman’s pipevine thrives in U.S. Department of Agriculture plant hardiness zones 8 to 10, blossoms in winter, climbs tree trunks without doing injury and attracts Pipevine swallowtail butterfly caterpillars. Heucheras grow well in zones 4 to 9. Although a lot of species like moist ground, three that bear dry soil are Lillian’s Pink coral bells (H. “Lillian’s Pink”), Rosada coral bells (H. ‘Rosada’) and island alumroot (H. maxima).
Some trees, like the California black walnut (Juglans hindsii), produce toxic chemicals that not only keep weeds under control but also cause many plants to wither. Black walnut species are especially poisonous due to the juglone in their roots and leaves. Bugleweed (Ajuga reptans), creeping phlox, heath aster, heucheras, and sweet woodruff (Gallium odoratum) are good perennials for landscaping near black walnut trees.