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Sandy's Garden

Growing Lawns in the Shade

Shady lawn areas create extra challenges

By: Sandy Feather 2010
Penn State Extension


Q. We have a heavily wooded lot, and growing grass seems to be more difficult each year. We have a "growing" area of bare earth and increasing areas of moss. How do I get grass to grow in a wooded/shady area, and how do I effectively get rid of the moss?
  
  A. The first step is to make sure you're growing varieties of grass that tolerate shade well. Most grasses prefer full sun. Fine fescues, such as creeping red fescue, hard fescue and Chewings fescues, are well adapted to shade, particularly dry shade. Turf-type tall fescues also tolerate shade well. Rough bluegrass takes damp shade, but it is not a particularly attractive grass.
  

Bluegrasses

Although most Kentucky bluegrass varieties prefer sun, there are some that tolerate shade, such as Bristol, Eclipse, Georgetown, Glade, Midnight and Sydsport. The best shade mixtures are roughly 60 percent fine fescue and 40 percent shade-tolerant Kentucky bluegrass varieties.
 
There are other steps to help your shady lawn. It is helpful to limb up the trees a little and have the canopies thinned to allow more sunlight through. You should hire a certified arborist to prune large trees. They have the training and equipment to do the job correctly and safely.
 
Besides casting shade, established trees compete with the turfgrass for water and nutrients. This might not be a problem for you because you have moss, indicating that excessive moisture may be more of an issue. In most other cases, water deeply once or twice a week when there is no rain, applying at least an inch of water at a time. This means setting up your sprinkler to apply about a half-inch of water an hour because that is what our clay soils are able to absorb without runoff. If the area is sloped, you may have to apply the water more slowly to avoid runoff.

Lawn in shade

You should also fertilize shaded turf at a slightly higher rate than you would otherwise. Although you should start with a soil test, using a slightly higher rate of nitrogen will benefit the grass.
 
Fine fescues ordinarily require 1 to 2 pounds of nitrogen per 1,000 square feet over the growing season. To make up for the competition from the trees, 2 to 2-1/2 pounds of nitrogen per 1,000 square feet should be sufficient. This should be split into at least two applications in late spring (mid-May) and late fall (mid-November). If you prefer three, divide the nitrogen into three applications, adding one in late summer (early to mid-September). Turf-type tall fescue ordinarily takes 2 to 3 pounds of nitrogen over the growing season. To compete with trees, raise that to 3 to 31/2 pounds.

fertilizer

Rough bluegrass and Kentucky bluegrass prefer 3 to 4 pounds of nitrogen per season. Under trees, use the 4-pound rate. Use the same timing suggested above.

Calculations

To calculate how many pounds of fertilizer you need, divide 1 pound by the percentage of nitrogen in the fertilizer. For example, how many pounds of 32-3-5 fertilizer are required to apply 1 pound of nitrogen per 1,000 square feet to a 5,000-square-foot lawn? Thirty-two percent is the amount of nitrogen, 3 percent is the amount of phosphate, and 5 percent is the amount of potash. These nutrients are always listed on a fertilizer bag in the same order.

1 .32 = 3 pounds

Multiply the 3 pounds by 5 to find that it takes 15 pounds of 32-3-5 for a 5,000-square-foot lawn. Simply substitute the analysis of the turf fertilizer you normally use and the size of your lawn to calculate how much is required to apply the suggested amount of nitrogen.

Mowing is Important

It is also important to maintain a higher cutting height when mowing shaded turfgrass. There is a directly proportional relationship between the topgrowth of the grass and the depth of its root system. The shorter you cut it, the less root system it has to compete with the trees. Leaving the grass longer also shades out germinating weed seeds. (It is important to control weeds on shaded turf to eliminate their competition for water and nutrients. The fact that turf in shaded areas is often thin creates an ideal opening for weeds to creep in.)

shady lawn

Finally, keep leaves off the grass as they block out the sun and starve the roots by interfering with photosynthesis. This weakens the grass plants and makes them more susceptible to other stresses because they cannot manufacture sufficient energy reserves.

Moss

There are a number of factors that create an ideal environment for moss: moisture, shade, soil compaction (because it reduces drainage), low soil pH and low soil fertility. Excessive moisture is the most important factor. Moss will grow in full sun and alkaline soil as long as there is moisture.

Hiring an arborist to thin the crowns and limb up the trees will allow more sun to reach the ground and speed drying after it rains. Core aeration followed by a thin top dressing of compost -- one-eighth to one-quarter inch -- will help alleviate soil compaction and improve drainage. You can have the soil tested and apply lime and fertilizer to favor the growth of grass.

OR ... you might want to consider working with what you have and not struggling to grow grass in an environment that does not naturally support its growth very well. You might create lightly mulched beds under the trees -- perhaps you can encompass groups of them in a single bed and underplant them with shade-tolerant shrubs and perennial plants such as ferns, hellebores and native bleeding heart plants. And dare I suggest ... moss?

Something other than Grass

When you plant shrubs and perennials under trees, do not work up the whole area; just dig holes twice the size of the rootballs and plant the plants.

groundcover in shade

Arrange for the mulch to extend out from the trees the length of their limbs (known as the drip line). Two inches of mulch is all that is necessary. You can place it close to but not touching the bases of the tree trunks. Trees and grass have many opposing needs. Grass prefers a higher fertility level and more neutral soil pH than many native trees. Changing the soil chemistry to favor grass will spell trouble for the trees over time.

Test Soil

Penn State soil test kits are available for $12 each. If you purchase more than one kit at a time, additional kits are $9 each. Make checks payable to Penn State Cooperative Extension and indicate the number of kits you want. Send to Soil Test Kits, Penn State Cooperative Extension, 400 N. Lexington St., Pittsburgh 15208.

More

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Trees and Shrubs for Shade

 

   

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