Growing grass in the shade is problem for which there are no easy answers. Grass is a full-sun plant and when planted in shaded areas (defined as a site that receives less than 4 to 5 hours of direct sunlight daily) it performs poorly. The filtering effect of trees significantly reduces the amount and quality of light grasses receive. This has an adverse effect on photosynthesis, the process that produces energy needed for the grasses to grow. What we see from this effect are grasses that are thin, weak, and have a lower tolerance to disease, drought and wear stress.
There are a few management practices that may help reduce the problems associated with growing grass in shade. Some of these practices are explained below:
- Select shade tolerant grasses when possible. Cool-season grasses like fine fescues (chewings, red, sheep, and hard fescues) have excellent shade tolerance but are not tolerant of high temperatures. Traditional tall fescues can tolerate high temperatures but are less tolerant of shade. Warm-season grasses have even less to offer in shade tolerance. Bermudagrass has extremely poor shade tolerance while Zoysia cultivars (i.e., El Toro, Cavalier) can tolerate light shade but tend to die out in a few years.
- Raise your mowing height. Turf growing in shade needs a large leaf surface to intercept as much available light as possible. Raise your mower blade to 3 inches or higher. Also, mowing more frequently is beneficial since shaded grasses have a tendency to grow long and narrow. Cutting excessively long grass will affect root growth and thus nutrient and water absorption by the plants. Remove clippings to prevent further reduction of light to the turf.
- Reduce fertilizer applications. Lawn grass in shade requires only half to two-thirds as much nitrogen as grasses in full sun. Over-fertilizing can increase disease incidence and deplete grass carbohydrates resulting in a thin turf. Maintain proper soil pH, potassium, and phosphorous levels by soil testing.
- Reduce water usage. Grasses in shady areas require less water than grasses in full sun. Water on an “as-needed” basis (i.e., when leaves begin to roll up, when impressions from foot traffic remain on the grass). When you do water, avoid shallow watering which encourages shallow roots.
- Evaluate and modify existing trees. Trees that have open canopies and deep roots are more conducive to turf than those with dense foliage and shallow roots. Some tree species that cause fewer problems are sycamores, oaks, and elms. Undesirable trees include willow, popular, and some maples. Selectively pruning branches, especially low branches, can aid in light penetration. Ideally, the lowest branches of trees should be 6 feet above the soil surface. Topping trees is not a recommend practice. If grass is a must, consider removing one or more trees that are contributing to the heaviest shade.
Submitted by Kelly Jackson, Agent for Horticulture, Christian Co. Cooperative Extension Service