Shade Issues & Opportunities

In the lawn care and grounds maintenance industries, most properties are blessed with some shady areas. There are few sites that have no shade, perhaps with the exception of new construction. Yet, even these sites have shade, as the buildings, homes, awnings and covered walkways cast shadows. Inevitably, lawn care operators and landscape maintenance contractors must deal with shade as a given in the landscape.

Shade affects turf and ornamentals. The effects of shade are complex, with a lot of interrelationships between turf, ornamentals and non-plant materials in the landscape. Shade affects the function of the site. Heavy levels of shade prohibit the growing of turf, which limits traffic in an area. No other plant is as traffic tolerant as turf.

If you’re dealing with a shady area and you decide to replace turf with groundcover, expect a change in function, as well. And clients used to walking or letting children play in the shady area may also need to change their expectations for that area as well.

SHADY ISSUES. Each type of shade will impact the landscape differently. These are the different types:

• Light shade – mostly open conditions with eight to 10 hours of full sun. Light shade is likely to occur in landscapes containing only small trees.
• Dappled shade – light to moderate shade produced by a pergola; a small-leaved shade tree such as a honeylocust; or an open canopy tree, like an Amur Corktree or a Kentucky coffeetree.
• Half shade – morning sun/afternoon shade – four to five hours of each. Some plants will grow well placed in morning sun, but not so well in afternoon sun, like Barrenwort or Bishop’s Weed.
• Mostly shady – six to eight hours of dappled or full shade.
• Full shade – no significant periods of sunlight during the day.

With problematic shade, let a site inventory/analysis help classify the landscape. This task is best performed on-site by gathering information, taking notes and gaining a "sense of place" in the landscape space.

Inventory is first. Determine the level of shade and identify the area's problem spots and assets. Using a light meter can help determine the intensity of sunlight in the area. You can purchase or borrow one from a lighting contractor or use the light meter in a camera.

Next, use a piece of tracing paper and lay it over a base map of the area. Base maps are easily obtained from commercial clients, but they can be a bit more difficult to obtain for residential properties. This exercise allows accurate note taking and documentation of potential concerns or opportunities for features. You may want to photograph the area for future reference and comparison. If you implement a change that turns out well, you may want to use the "before" and "after" photos to sell a job to another customer.

Analysis comes later, with an evaluation of each specific condition's importance. The soils, neighboring views and existing buildings may be only slight concerns, but the level of shade and prevailing winds may be major contentions.

After you have identified the level of shade, write "heavy shade" or "light shade" in appropriate portions of the landscape renovation plan. If you are using a light meter, write the number of footcandles of light in the circle with the description. This will be a valuable reference when you are considering changes to the area.

RIGHT PLANT, RIGHT PLACE. This catch phrase of recent years is appropriate when considering shaded landscapes. Placing well-adapted plants into shady spaces is critical to the landscape’s success.

Determine the specific needs of each plant in the space and match it to a suitable location. For example, a landscape on the north side of a house with an oak tree located 25 feet from the foundation and several grey dogwoods or redbuds growing in the understory will have four to six previously identified types of shade. Certainly, heavy shade will be present under the oak, while dappled or half-shaded conditions may exist on the edge of the dripline, depending on the exact location of the understory trees. As you introduce other plants into the landscape, keep the different levels of shade in mind.

Poorly sited plants will struggle. Placed in more shade than originally intended, plants may develop leggy, stretched out stems. This tissue is generally floppy and abnormal in appearance. Moss, mildew and slugs are more likely. The long-term, end results are dead plants and unhappy clients.

COMPETITION. Turf and ornamentals fail in landscapes because of excessive shade and plant competition. Both factors impact the survival of plants growing underneath the canopy. Recent research studies show that between 85 and 90 percent of a tree’s roots are in the upper 18 inches of the soil surface, which is the exact location of a new ornamental’s roots that are trying to establish themselves, as well as the entire root systems of most turfgrasses.

In addition to normal competition from trees and large shrubs, walnut trees produce anti-competitive compounds in their roots, which actually act as a herbicide toward many plants that try to grow nearby, or in the same location. Be aware of this when you choose plants for a shady landscape.

OPPORTUNITIES. The landscape manager or lawn care operator needs to look at a problematic shade area as a potential sales opportunity. A little positive mental attitude will go a long way in turning a problem into income for your business. Here are four basic redesigns for shady landscapes:

Replace existing ornamentals with shade-adapted ornamentals. Existing plants are likely to be growing, although not that well. Lilacs and chrysanthemums will grow in the shade, but they won’t flower. Likewise, burning bush will produce green foliage that doesn’t turn bright red, as it would in full sun. Look to match the hours of available sunlight in an area with plant needs.
Replace existing turf with shade-adapted turf. Existing turfgrasses are also likely to be struggling in low light. In general, turfgrass isn’t a viable plant choice in areas that receive less than three or four hours of sun each day. Consider replacing Bermudagrass or Kentucky bluegrass with a fine fescue, tall fescue or supina bluegrass.
Replace existing turf with shade-adapted ornamentals. Forget about turf if the area receives less than three to four hours of sun daily. Spray the existing struggling turf with a nonselective herbicide, wait a week or so, and then plant adapted perennials and groundcovers.
Turn an existing failed mixed landscape into one with no, or few, plants, by installing hardscape elements. In heavy shade, consider using mostly mulch and stones as groundcover and an alternative to turf. A series of paving stones, flagstones or cobblestones running through the landscape facilitates traffic flow and creates a sense of motion, which can be very appealing.

Another opportunity to serve the client is through tree pruning. Whether you subcontract this work out to a colleague or provide this yourself, certified arborists can improve the potential for better plant growth with judicious pruning. The key is to open the canopy and allow more light to penetrate through the tree. In general, light pruning is the rule. Never remove more than 10 to 20 percent of the leaf surface within a given year.

Pruning is most successful when it is done to enhance the growth of existing, shade-adapted plants. Attempts at pruning to allow plants that require more light to thrive generally fail because the tree canopy grows back in a few years, and the new plants starve for sunlight. Tree pruning is more effective when only one tree is present in the landscape, rather than several existing specimens.

Once the canopy has been opened up, then shade-adapted turfgrasses can be introduced into the landscape. Select a seed mixture that combines several shade-tolerant cultivars of each species. In a shady environment, the best results are achieved with this approach. St. Augustinegrass and bahiagrass may function well in warm-season regions, while cool-season turfgrasses can be used in northern areas.

In moist shade, select a mix that is 20 percent rough bluegrass; 10 percent supina bluegrass; 40 percent fine fescue; 10 percent perennial ryegrass; and 20 percent shade-adapted Kentucky bluegrass cultivars. Cultivars of Kentucky bluegrass that perform well in shady conditions include America, Chateau, Explorer, Glade, Nuglade, Princeton 105 and SR 2000.

On dry shade sites, a mixture of 50 percent fine fescue, 40 percent shade-adapted Kentucky bluegrass cultivars and 10 percent perennial ryegrass should be sown. Supina and rough bluegrass should not be used because these species perform well only in a moist environment.

MAINTAINING SHADED TURFS. Plant growth regulators (PGRs) can significantly improve the quality of turf growing in the shade. They work by slowing vertical leaf elongation, which channels more food into the stolons, crown and roots of the plant, and leaves more food available for root growth. When plants treated with PGRs are compared to untreated plants, the treated plants are thicker and denser, with more roots. Untreated plants tend to be thinner, paler and scant in comparison.

Use product mixtures of slow-release nitrogen fertilizer and PGRs to encourage root growth and to strengthen crowns.

Apply 1 to 2 pounds of nitrogen per 1,000 square feet per year in shaded areas. Slower- growing plants are unable to use high levels of nitrogen for desirable results. Shaded turfgrasses that receive heavy fertilization will become weakened. Apply fertilizer at the same times of the year as sunny areas, just apply less.

Another maintenance practice to pay attention to in shaded areas is mowing. If possible, mow the shaded turf areas a at a higher height than the sunny turf ones. Shaded plants need all the leaf surface area they can get for photosynthesis and to send carbohydrates and sugars to the roots and crowns. This is especially important for grass plants in the shade because they have fewer leaves than ones in the sun.

Also, try to instruct your clients to limit traffic in shaded areas. Because turf in these areas is not growing vigorously, it struggles to tolerate traffic. Installing pavers or stepping stones is helpful in shaded turf areas, just as it is in shaded mixed landscapes.

Irrigate turf in the shade a bit less than the sunny areas of the landscape. Set the irrigation controller timers for the "shady" zones to run for approximately 80 percent of the time, as the sunny zones do. The shady areas dry out slower and are more likely to retain moisture because there is less evapotranspiration. If shady turfs are irrigated the same amount of time as sunny areas, more water than necessary is applied, increasing the potential for root rot, compacted soils, moss and mildew.

Maintaining a healthy landscape in shade is a complex endeavor. Using some of the strategies I've suggested may increase your success.