IS MY TREE KILLING MY GRASS?
Why’s my grass declining underneath my trees? We run into this question frequently and there isn't always one answer. So below, we are going to discuss some of the "primary factors" that could be contributing to the decline of your turf underneath your trees!
1) DENSE SHADE
If you have a large, mature tree or if you have multiple trees in a smaller area, it may be an option to raise or thin the canopy of your trees. Be careful not to sacrifice the health of the tree for the grass however. It would be a good idea to consult a certified arborist for their recommendations on the matter. Also, for those problematic areas underneath the trees, be sure that you are mowing the grass a little taller. The taller the grass, the more photosynthetic capacity the grass will have. The more photosynthesis occurs, the better the root growth and overall health of the grass will be. The shorter you mow it, the worse the grass will perform.
2) WRONG TURF TYPE
Bermuda, zoysia and buffalo grass do not do well in the shade. If you would like to have grass underneath your trees, be sure that you are seeding with fescue, bluegrass, or possibly some rye grass. Cool season grass requires fewer hours of sunlight to thrive, typically about 3 hours per day, where warm season grass will require about double that.
3) DROUGHT CONDITIONS
Every plant requires moisture. We don't always think about watering our turf during the winter, but in the dry winters that we have been experiencing the last several years, we are seeing a LOT of turf decline as a result of root desiccation. If possible, even during the winter months, if the soil isn't frozen, try to water deeply once every week or two. During the spring and summer, we want to apply approximately 1-1.5 inches a week. This will be one of the most important habits regarding turf health underneath trees.
4) TREE ROOTS ELIMINATING AVAILABLE SOIL
This is a problem especially underneath maples, sycamores, and ornamental pears. Tree roots
will not necessarily outperform grass roots, but if there are not ideal growing conditions for your grass underneath your trees, the tree roots will continue to inhabit that area (which is a good thing). As the tree roots get bigger however, the less soil there is available for the turf. In these situations, we recommend applying a mulch bed underneath your trees to resolve this issue. It is less maintenance for you, mulch is so much better for the tree, and you don't have to worry about reseeding every year! You can also place shade tolerant annual or perennials in the mulch bed as well!
5) Compaction from traffic or mowers?
We see this often, but it is seldom thought of as a cause of the problems. If there is an area underneath the tree that is declining, but it gets plenty of sun, it's watered well, good growing conditions, etc...it may be a compaction issue. The more foot traffic or the bigger the mower we use, the more likely compaction occurs underneath our trees. If there is a lot of foot traffic in the area, consider installing a walking path or a mulch bed. When mowing, be sure not to water the lawn a day or two prior to mowing so the soil has an opportunity to dry out. Saturated soil compacts way easier than dry soil. The weight of the mower compacts the soil, leaving the growing conditions underneath the tree less than ideal for the turf and the trees.
6) Trimming grass too short?
This is another common problem. Typically, the grass underneath mature or dense trees will not receive as much sunlight as the turf outside of the shade zone. So, as mentioned above, if we
or mow the grass too short, we lose photosynthetic capacity. Since it's in the shade, we want the grass to be taller. The bigger the blade, the more opportunity the grass will have to collect the sunlight it needs to produce the food that the plant requires to thrive in a shorter amount of time. So, if your mowing or if your weed eating, this is really important to remember.
7) Declining soil health/low organic matter?
Lastly, probably the most overlooked, is the health of the soil. When we have an area underneath a tree that has not had any kind of vegetation underneath it, then that thin area gets blasted by direct sunlight through the winter months, the health of the soil will begin to decline. Soil needs organic matter. While root cycling from the tree does provide some organic matter, often times
it's not enough to maintain ideal soil health for growing grass. So if your desire is to have grass underneath your tree, you may consider introducing and incorporating some good compost underneath the tree to provide a healthier seed bed for your new grass. Again, mulch is a great option for this as well and much more beneficial for the tree if you are willing to sacrifice additional turf space for tree health.
There are many reasons why the turf underneath and next to your trees may be struggling, so if these don't answer your questions, reach out to us and we will see how we can assist you. It'd be our pleasure to help in any way that we can!
