How Shade Affects Lawn Grasses
Lawn grasses need light, air, water and nutrients — just as all plants do. Trees, shrubs and buildings that shade parts of your lawn can keep grasses from getting these essentials, impacting your lawn above and below ground. Leaves on trees and shrubs can prevent light and water from reaching grass below, while roots from the same plants take water, nutrients and oxygen away from grass roots. Shade can also cause soil to retain too much moisture and compound drainage problems that exist.
In shade, grasses stretch to reach sunlight and grow thin and weak, much like houseplants that grow tall and spindly as they lean toward window light. Grass grows weaker, loses its attractive color, and becomes more susceptible to additional stresses, including insect pests and lawn disease.1,2 Roots on shaded grass grow shallow, and growth slows.
The effect of large trees even stretches beyond areas that lie in shade. Tree roots can cover an area up to seven times the shaded area beneath the tree's branches. Even on very large trees, more than 50 percent of those roots stay in the top six inches of soil — primed to compete with grass roots.
Lawn Grasses and Shade Tolerance
If you're an outdoor person, you already understand that noontime sun is stronger than gentle morning rays. Sun and shade patterns change throughout the day and through the seasons, as trees and shrubs leaf out in spring and drop leaves in fall. Take time to assess your shade patterns closely, so you understand what grass is up against. Then you can select grasses best suited to the challenge.
Your first decision in choosing seed involves warm- and cool-season types. This is determined primarily by where you live. Warm-season lawn grasses thrive in more southern and western zones, while cool-season grasses flourish in more northern areas. Zoysia grass is one of the best warm-season grasses for shady conditions. Bahiagrass and Centipede grass have moderate shade tolerance, but Bermudagrass doesn't do well without full sun.
Cool-season grasses generally tolerate more shade than warm-season types, but they vary, too. Fine fescues have the greatest shade tolerance among common cool-season grasses, while tall fescues do well in moderate shade.1,2 Perennial ryegrass and Kentucky bluegrass need more sun, but some varieties tolerate light shade well.
Adjustments to Help Shaded Grasses
- Let more light in. Even shade-tolerant lawn grasses perform better when given more sun. Whenever possible, trim trees and shrubs to open their canopies. This increases sunlight and improves air circulation, which can benefit your trees and shrubs as well as grasses. For new plantings, consider plants that are naturally open and less dense.
- Restore soil balance. In shade, soil conditions get unbalanced quickly. Low soil pH and poor drainage set the stage for tenacious weeds and undesirable lawn mosses to move in. Soil testing and soil amendments, such as Pennington® Fast Acting™ Lime, can help restore pH to optimal balance and increase the availability of grass nutrients. Dethatching or aerating compacted soil at the proper time can help alleviate drainage problems.
- Increase mowing height. Mowing higher than normal gives grass more blade surface to capture and process available sun. Higher mowing also encourages deeper roots, which can improve grass resilience and health. Always follow best mowing practices and never remove more than one-third of the blade in any one mowing, or you'll add to grass stress.
- Adjust fertilizer and irrigation schedules. Shaded grass grows more slowly than grass in sun. While fertilizer can spur growth, stressed grasses can't handle the same amounts as healthy, sun-fueled lawns. Similarly, slow-growing grass generally needs less water. However, competing trees roots can limit available water and nutrients. Monitor your lawn closely and adjust your care to meet the special needs of shaded spots. A turf professional or your local extension agent can help with information and advice.
- Limit lawn traffic. Weak, stressed grass is prone to damage from foot traffic, pets and kids at play. Relocating play areas and limiting foot traffic helps. When damage occurs, repair bare spots with a premium product designed specifically for tough shade areas, such as Pennington® One Step Complete Dense Shade™.
Alternatives for Shady Areas
When your shade is simply too dense for attractive grass to grow, even with adjustments to care, you still have plenty of options to beautify your yard. Low-growing, spreading plants, called ground covers, come in many different colors and textures to fill sun-challenged areas with foliage and even blooms.
Vigorous, ground-hugging periwinkle offers glossy green leaves and star-shaped blue flowers. Native Pennsylvania sedge provides a meadow-like, grassy look. Low-growing native wintergreen adds berries to the mix, while shade-preferring perennials and annuals, such as hostas, painted ferns or colorful coleus, help brighten shady spots while filling in.
Shade areas also offer great opportunities for peaceful resting spots to escape summer heat. Shady trees that trouble lawn grasses provide welcome relief for people and pets, and make perfect backdrops for benches or Adirondack chairs surrounded by shade-loving flowers. Add the soothing sound of a bubbling fountain or birdbath and problem lawn areas become spots you seek out.
Whatever your lawn goals and challenges, you can turn to Pennington and the full line of Pennington® grass seed and lawn and garden products for help. Pennington is committed to growing the finest grass seed possible and providing you with premium products, timely email tips and expert advice on your way to lush, healthy lawns and gardens.Pennington, Smart Seed and One Step Complete are trademarks of Pennington Seed, Inc.
Fast Acting is a trademark of Encap, LLC.Sources:
1. Harper, J.C., “Growing Turf Under Shaded Conditions," PennState Center for Turfgrass Science.
2. Patton, A., “Growing Turfgrass in Shade," University of Arkansas Cooperative Extension Service.
3. Iowa State University Forest Extension, “Roots in Depth," Iowa State University, January 2012.