During a sultry Texas summer, we really appreciate a little shade in the landscape, so a large tree can be a great asset. But we also appreciate a lush, beautiful lawn — and turf and trees tolerate each other at best.
Warm-season turfgrass requires a significant amount of sunlight to maintain acceptable growth and density. For best results, a minimum of four to six hours of direct sun is needed, although a bright, dappled shade over the course of the entire day may be enough. Less sun means a progressively thinner, weaker stand of grass.
Among our southern turf species adapted to the Bryan-College Station area, St. Augustine is the most shade tolerant. If a spot is too shady for St. Augustine, it is too shady for any warm-season lawn grass. Zoysiagrass is next, followed by centipedegrass and finally by bermudagrass, which is by far the least shade tolerant.
In a landscape filled with trees, the light intensity the grass receives decreases a little each year as the trees grow larger, blocking more and more of the sun. So, it is no surprise that a shady area where grass once thrived can begin to decline over several years.
Once a lawn begins to thin out from lack of sunlight, other complications likely will arise. Soil structure will be lost as foot traffic creates compaction, reducing water infiltration, aeration and root growth. Weeds often become a problem in these spots, further stressing the remaining grass.
Turfgrass weakened by a lack of sunlight is more susceptible to some disease problems, and lawn care practices that may be fine in sunny areas can exacerbate problems in the shade. A natural response to thinning turf is to water and fertilize more to “make it grow faster and fill in better.”
Extra watering also is counterproductive, as this can increase some diseases; in fact, grass uses less water in the shade than it does in sun.
The bottom line is that while sunlight, nutrients and moisture are all needed for strong growth and good grass plant health, you can’t make up for a lack of sun by adding more of the other two.
If you have a shady spot where the grass is not thriving, here are several tips to help improve your lawn:
• Avoid compacting the soil. Reroute the pitter-patter of little feet, both people and pets, until the area fills in. Areas that are already compacted may benefit from mechanical aeration. You can rent a machine or hire a lawn care professional.
• Set your mower higher for shady spots. The leaf blades of the grass are its solar panels. More leaf area enables them to capture more light to support new growth. Plus, it makes thin areas look a little thicker than if they are mowed shorter.
• Avoid the temptation to over-fertilize. Turf growing in the shade requires less nitrogen, not more. Extra nitrogen results in the plant pushing more leaf growth at the expense of root development. But without solar rays to drive photosynthesis, there isn’t the carbohydrate production needed to build a stronger grass plant and to increase turf density.
• Avoid the temptation to over-water. As with nutrients, you can’t make up for a lack of light with extra water. In fact, heavily shaded areas use only 1/2 to 2/3 as much water. Over-watering also can result in increased disease problems.
• Sometimes selective tree trimming by removing some branches around the lower periphery of the tree canopy can help allow a little more light in from the sides. If the shade is not too dense to begin with, this may be somewhat helpful. However, pruning throughout a tree enough to make the turfgrass thrive is generally not recommended since doing enough pruning to make a big difference is detrimental to the tree’s structure and form. It is also only a temporary fix; the tree will quickly regrow, often creating a denser shade in the long run.
• If the shade is marginal and you have taken some of the above steps, planting plugs or sod strips in bare areas can help speed reestablishment of the turf as it tries to fill back in under less than ideal light levels. Otherwise the new plugs will just decline along with the existing turf.
These tips, although helpful, will not guarantee a lush lawn in heavy shade. Let’s face it, some spots are just too shady to grow grass. Shady spots can become mulched areas with outdoor seating, or planted with very shade tolerant groundcovers, perennials and shrubs. With a little planning and creative design, these areas can become a beautiful addition to the landscape.