Lawn and Shade Problems and Corrective Measures

This bulletin is to give people who have, or suspect they have, a shade problem on their lawn, a method to determine the extent of the problem and suggest courses of action to correct the problem.

Problems

Typical problems associated with a shade environment compared to grass grown in full sun are:

Symptoms

Common symptoms of shade grown turfs are:

Defining Shade

The traditional practice of defining shade as light, medium or heavy, without attaching a value, is almost useless. Therefore, the following values are used for purposes of discussion.

Full Sun--100% of the daily available sunlight. This is the optimum for good turf development.

Light Shade--Less than 100% but more than 75% of the daily available sunlight reaching a particular area. This range of sunlight should not present a problem for lawn maintenance.

Medium Shade--Less than 75% but more than 25% of the daily available sunlight reaching a particular area. This range is good to fair with the ability to maintain a satisfactory lawn becoming increasingly more difficult as the total available light diminishes to 25%.

Heavy Shade--Less than 25% of the daily available sunlight reaching a particular area. It is very difficult to establish and maintain a lawn at this light level. Choose a more shade-tolerant ground cover.

Average Light Intensity

The average light intensity of a given area can be determined by taking a light meter reading at 9:00 a.m., noon, and 3:00 p.m. When the leaves are on the trees, take a reading in the shaded area and one in full sunlight. Total the readings of each area separately. Divide the sunny area total into the shaded area total to determine the percentage of sunlight in the shaded area. If the average is below 25%, consider reducing the shade or growing a more shade-tolerant plant.

Example:
Sun Shade
9:00 a.m. 4000 900
Noon 8000 1400
3:00 p.m. 7000 200
19000 3500

3500+19000=18.4%

If the decision to reduce the shade is made, another reading should be taken after the work is completed to be sure enough light is available for good grass growth.

A light meter calibrated in foot candles is needed to take the light measurements. If one is not available a photographic light meter, hand held or built into a camera, can be used with the following formula:

20(f)2

Foot candles= TS

F-f stop (aperture opening)

T=exposure time in seconds or fraction of a second (shutter speed)

S=film speed (ASA)

Place a piece of white paper, 8 x 11 inches or larger, on the ground and take a reading by pointing the meter or camera toward the paper. The meter or camera should be nine to 12 inches away from the paper. When taking the readings, the same meter or camera should be used at the same spot and the same distance away from the paper. The readings are recorded and converted by using the formula.

Example:

S(ASA)=100

f (aperture opening)=8

T(shutter speed)=1/60



Footcandles= 20(8)2 =  20(8x8) =  20x64  = 1280  = 1280

             -----     -----      -----   -----   -----  = 766

           1/60x100   1/60x100  1/60x100  100/60   5/3


The formula yields the following results if the ASA. is set at 32 and the exposure time

(read at f stop 5.6) is:
Exposure Time in Seconds
Foot candles
1 19.6
1/2 39.2
1/4 78.4
1/8 156.8
1/15 294.4
1/30 588.8
1/60 1177.6
1/125 2450
1/250 4900
1/500 9800
The accuracy is +/- 20% using the above formula, depending upon the cone of light accepted by the meter. However, provided the same meter is used to take all the readings, it is accurate enough in determining the percentage of light reaching the shaded site.

Reducing the Shade

It may be possible to establish and maintain a respectable lawn in a shaded wooded site by removing some trees. Trees should be spaced far enough apart for good air flow and light penetration. Forty to sixty feet apart is suggested.

Low branches on trees should be removed to a height of 10 feet or more. This will allow more early morning and late afternoon light to enter the area. Thinning the tops of dense trees will allow more light to penetrate the tops. Thinning is the selective removal of some small and large branches.

Cultural Practices

Lawn Establishment--Lawn establishment in a shaded site is more likely to be successful if seeded in early fall (mid-August through September). The area then has the maximum length of time with the leaves off the trees. This should allow good root and tiller development. It is extremely important to continually remove the fallen leaves. Sodding can be done at this time if the sod contains the correct species of grasses. Most sods are predominantly Kentucky bluegrass which is not well adapted to shade.

Once the lawn is established, mow the grass to a height of two to 3 inches. The longer leaf blade will have a larger surface to gather sunlight. This will result in a stronger plant.

Fertilizing--Fescues, the dominant grasses in shade grass mixes, are not tolerant to high levels of nitrogen fertilizer. Therefore, apply fertilizer only once or twice a year. Limit each application to one pound of actual nitrogen per 1,000 square feet. The first number of a fertilizer grade on the bag is the percent nitrogen by weight. For example, a 10-pound bag of 10-6-4 contains one pound of nitrogen.

If a once-a-year fertilizing program is chosen, apply the proper amount of fertilizer in late April or November. With the two application programs, the fertilizer should be applied in late April and early September or early September and November.

It is important to maintain the proper pH of the soil. Have it tested every two to three years. The pH is maintained by applying limestone, and the amount of limestone required is determined by the soil's present pH and its texture.

Watering--Water only when it is necessary during prolonged dry periods. Apply one-half to one inch of water, not more than once a week. Place a few cans in the sprinkler pattern to measure the water depth. To reduce disease problems, water in the early part of the day so the grass will dry before nightfall.

Traffic--Limit the amount of traffic and play activity in the shaded site. This will reduce the damage to the thin-bladed grasses that are slow to recover.

Compacted Soil--Loosen compacted soils by aerating or, if the grass needs replanting, till the area to make a good seed bed.

Bold--Remove leaves every few days as they are shed by the trees in the fall. A thick carpet of leaves will smother the weakened grass plants.

Diseases--If fungi become a problem, apply the correct fungicide at the proper time and rate.

Shade-Tolerant Grasses

The fine-leafed fescues and the newer turf-type tall fescues are the preferred grasses for dry, shaded sites. Arid, Mustang, Rebel II and Titan are turf-type tall fescues. In the fine-leafed fescues try SR3000, Reliant and Spartan which are hard fescues or Jamestown and Victory which are chewings type fescues. A few varieties of Kentucky bluegrass have shown improved shade tolerance. These include Adelphi, A-34 Bensun, Baron and Liberty. Where the shaded site remains wet most of the year the rough bluegrass, Poa trivialis L. will do better.

Alternate Ground Covers

Sites that do not have at least 25% of the available sunlight should be planted to another ground cover more tolerant of shade. A few are English ivy, Hedera helix; Japanese spurge, Pachysandra terminalis; or myrtle, Vinca minor. By planting an alternate ground cover in the heavily-shaded site, the homeowner can avoid the annual frustration of replanting grass seed only to see it die by midsummer.

Prepared by:
Edmond L. Marrotte, Consumer Horticulturist, University of Connecticut

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 products referenced or imply approval of the product to the exclusion of others which also may be available.All agrochemicals/pesticides listed are registered for suggested uses in accordance with federal and Connecticut state laws and regulation 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! Agrochemicals/pesticides are dangerous. Read and follow all instructions and safety precautions on labels. Carefully handle and store agrochemicals/pesticides in originally labeled containers out of the 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 current regulations. The user of this information assumes all risks for personal injury or property damage.Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Kirklyn M. Kerr, Director,Cooperative Extension system, University of Connecticut, Storrs. The Connecticut Cooperative Extension System is an equal opportunity employer

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