I have river birch with a dead circle of grass at the tips of the branches. As the tree grows this circle gets bigger. Why is this happening?
The Gardener’s Answer
Hello, Judy: It is often times difficult to get grass to thrive under any tree. While once there was healthy strand of grass, this can all change when you add a tree to the landscape. The grass may suffer due to competition in terms of light and moisture. As the tree grows so do the roots as well as the canopy. The grass will be shaded out by the foliage and the roots will always win when it comes down to who is going to get the water. So, you have a couple of options: first you can limb up the tree by removing some of the lower branches; this allow for better light filtration. You could also try planting more of a shade-loving grass such as creeping red fescue. If you are not married to having grass under the birch you could always under plant with shade-loving perennials such as ferns, hostas, and coral bells, just to name a few. Keeping the grass watered is essential in order for it to thrive. This is especially true during hot and dry summers. As the canopy expands so does the drip line. So when it rains the water is landing on the foliage of the tree and then rolls off the tips of the branches, eventually landing on the grass. The grass inside the drip line/canopy does not ever get that rainfall so it is up to you to make sure it receives enough moisture.