Growing Healthy Grass Under Shaded Conditions Is Often A Challenge For Homeowners

Growing lawns under shaded conditions By Steven Rackliffe, Extension Instructor Turfgrass Science, Department of Plant Science

Growing healthy grass under shaded photosynthesis, which leads to a conditions is often a challenge for reduction in carbohydrate production. homeowners. Shade occurs, to some When carbohydrate production drops, degree, in almost all lawns. Shade turf quality is negatively affected in a problems for turf may be reduced by number of ways, including, reductions improving the growing environment, in tiller production, rhizome selecting the proper variety of grass, or development, and root growth. Other altering turfgrass management practices. symptoms that shaded turf may It is important to have an understanding exhibit include succulent growth, finer as to how shade affects turfgrass growth leaf texture, reduced shoot growth before discussing the corrective and density, upright growth habit, measures that may improve the overall increased leaf length, and an overall health and quality of the turf under deterioration in plant vigor. As a shaded conditions. consequence, the turf “thins out” and becomes more susceptible to the The Shade Environment stresses of drought, disease, heat, Most turfgrasses require four to five cold and wear. hours of full sun, or a full day of filtered sunlight. In the majority of cases, shade Tree growth, age, and species will problems are the result of either dense affect the different light wavelengths tree canopies or locations on the north that shade turf. For example, a birch side of homes. Time of year also will have tree or a locust may allow light to filter an effect on shade as the angle of the through the foliage while large sun changes throughout the year. densely canopied trees such as Turfgrass growth is affected by the maples and oaks will absorb more of intensity, duration, and quality of light. the light wavelengths needed for Shade interferes with light wavelengths turfgrass growth. Newly planted trees that are necessary for carbohydrate create very little permanent shade. production through the process of When selecting landscape plants be photosynthesis. The light wavelengths aware of tree or shrub characteristics necessary for carbohydrate production at maturity and how they may effect are mainly orange, red, and blue light. turfgrass growth. A few questions that Light that filters through a tree canopy to should be answered before purchasing the turf below is usually low in these or planting should be: how tall will the wavelengths. The result is lower tree/trees be at maturity, how dense

1 will the tree canopy become, and what which, could lead to a reduction in are the rooting characteristics of the disease. It has been reported that trees or shrubs that are being selected? morning sunlight is more beneficial Shallow rooted trees should be avoided in than afternoon. One of the thoughts areas where turf grasses are a priority. behind this theory is that the grass Tree roots compete for nutrients and dries out in the morning sun and is water and may cause the turf to suffer less susceptible to disease. However, from nutrient deficiencies or drought more research is needed before this stress. Shallow roots can also damage recommendation can be made. Before lawn mowers. making the decision to selectively remove trees, one might try to prune Many times, in shaded environments trees and remove underbrush. Very turfgrass vigor is not only affected by often selective tree removal and shade, but by lack of air movement. Air pruning provides positive results. If flow can be impeded by obstructions pruning alone does not improve the such as houses, sheds, or more turfgrass quality then selective tree commonly underbrush and low branches. removal may be necessary. The Lack of light and air flow can result in an decision to remove trees is not an increase in the relative humidity, prolong easy one. What it comes down to in leaf and soil wetness after rainfall or many cases is that a choice has to be irrigation, and extend dew retention. made between a tree and grass. These conditions can lead to turfgrass disease and/or moss infestations. In fact, Grass Specie Selection much of the turfgrass thinning in shaded Another way that may help to increase conditions is the result of a combination turfgrass performance in shaded of low light intensity, high relative environments would be to plant humidity (disease), and root competition. turfgrasses that are better adapted to Improving the Growing Environment low light intensities. Table 1 illustrates The growing environment can be turfgrass performance under shaded improved by selectively removing trees conditions. or pruning branches (minimum 8-10 feet above ground level). This will reduce shade and improve air movement at the turf canopy. The result is increased light penetration and lower relative humidity

2 Irrigation: In areas of dense shade TABLE I monitor soil moisture levels prior to Shade Tolerance of Common watering your lawn. A reduction in soil and leaf wetness will promote Cool Season Grasses Utilized in healthier turf by decreasing turfgrass Home Lawns succulence and the chance for disease Poor infection. If water is necessary, water Excellent Good/Medium deeply and infrequently. When Creeping redTurf Type Tall Kentucky utilizing an underground sprinkler fescue * Fescue bluegrass system, the irrigation system should Chewings “Select” Annual be designed in such a way that allows fescue* Kentucky ryegrass areas of the lawn (in the shade) to be Hard fescue* bluegrass Perennial turned off or “run times” reduced. Rough cultivars ryegrass bluegrass** Mowing: Increase the mowing height in shaded areas by 0.5”- * grasses that perform best in dry shaded 1.0”. The increased leaf surface conditions ** grasses that perform best in wet shaded area will increase the ability of conditions the plant to absorb more light. A higher mowing height will also Management Practices for Growing result in a deeper root system, which will improve the availability Turf in Shade of water and nutrients to the Modifications of fertilization, irrigation, plant. and mowing practice will improve turfgrass quality. Soil pH: Soil tests should be taken periodically to determine soil pH. Fertilization: nitrogen rates should be If soil pH is below the reduced to at least ½ the rate that is recommended level, turf quality being utilized for turf grown in full sun. will be reduced. If the area is wet, High nitrogen fertilization increases poorly drained, and acidic, moss succulence which may result in increased and algae problems can develop. disease and traffic injury. Nitrogen also Extended leaf and debris cover encourages top growth of the plant at the expense of root growth.

3 from the fall can also increase soil the alteration of management acidity. practices, proper grass selection tree removal, and pruning has Leaf removal: In the fall remove failed, a decision must be made leaves frequently from turf under to choose between grass and tree canopies. A thick layer of leaves trees. If it is decided to keep the over weakened turf will further trees, alternatives to grasses aggravate the poor growing such as pachysandra, myrtle, or conditions. Increased incidences of another shade tolerant ground disease, lower pH, or, complete cover should be considered. death to the plant due to lack of light and oxygen are often the result.

The information in this material is for educational purposes. The recommendations contained are based on the best available knowledge at the time of printing. Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended. The Cooperative Extension system does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available.

All agrichemicals/pesticides listed are registered for suggested uses in accordance with federal and Connecticut state laws and regulations as of the date of printing. If the information does not agree with current labeling, follow the label instructions. The label is the law.

Warning! Agrichemicals/pesticides are dangerous. Read and follow all instructions and safety precautions on labels. Carefully handle and store Trafficagrichemicals/pesticides: If possible inlimit originally the labeledamount containers out of reach of children, pets and livestock. Dispose of empty containers immediately in a safe manner and place. Contact the Connecticut Department of Environmental Protection for currentof regulations. wear and The activity user of this in information shaded assumes areas. all risks for personal injury or property damage. Heavy traffic can further damage already weakened turf.

It is important to realize that under extremely shady conditions, most grasses simply will not perform. If