Trees out-compete turfgrasses for light, water and nutrients. However, the response of different cultivars to shade varies widely.

Trees are not going away from golf courses any time soon. They provide shade for players; make land use more efficient by separating fairways; increase golf course difficulty; enhance aesthetic value by screening roads, cars and buildings; protect errant shots from hitting pedestrians or cars; and provide a natural wildlife sanctuary and habitat for birds (Lilly, 1999).

Regardless of the shade source, turfgrass growth and development are inhibited when plant light interception is suboptimal. An estimated 25 percent of turfgrass growth is impacted by light restrictions (Beard, 1997).

Bermudagrass (Cynodon spp.) decline in shade can be attributed to excessive shoot production. Beard and Beard (2005) define shade as, "a turfed or ground surface overshadowed by plant foliage such as a tree canopy or by an opaque structure; typically the interception of sunlight occurs."

Photo 1

When light is blocked, bermudagrass stoloniferous growth slows and vertical growth is initiated in search of sunlight. Due to this morphological change, bermudagrass depletes carbohydrate reserves and severely reduces its recuperative ability from daily mowing, traffic and divots. Cultural practices to enhance turfgrass performance in shade include raising mowing heights (Bunnell and McCarty, 2004), applying plant growth regulators (Bunnell and McCarty, 2004), and reducing nitrogen rates (Bell and Danneberger, 1999).

Bermudagrasses are the most popular warm-season turfgrass in warmer climate zones in the country (Shearman, 2006). In order to assist turfgrass managers when selecting bermudagrass for establishment or for renovation when shade is a limiting growth factor, a study was initiated at Clemson University to determine how 64 percent continuous shade impacted 42 bermudagrass cultivars' growth and development.

Materials and methods

This two-year greenhouse study was conducted from June 15, 2005 to Aug. 15, 2005, and repeated in 2006 at Clemson University. The study included two treatments, a control (full sun) and 64 percent continuous shade, applied daily using a neutral density, polyfiber black shade cloth.

Table 1 Turfgrass quality of 42 bermudagrass cultivars after four and eight weeks of full-sun (control) and 64 percent continuous shade at the Clemson University greenhouse complex. NTEP turf quality (1 to 9).

Shade cloths were placed on a polyvinyl chloride (PVC) structure 6 feet in length and 5 feet in diameter with 1-inch diameter PVC pipes. Shade tents were placed 1 foot above the turfgrass surface to reduce sunlight encroachment in early morning and late afternoon.

Plugs were collected from the 2002 Bermudagrass National Turfgrass Evaluation Program (NTEP) (Table 3) field research plots located at Clemson University and transplanted into cone-tainers with 85 percent sand and 15 percent peat as growth media. Cone-tainer dimensions were 10 inches in height and 2 inches in diameter. Following potting, plugs were established one month prior to treatment initiation. Fertilizers were provided at 1 pound nitrogen (N) per 1,000 square feet biweekly using a complete fertilizer (16N-1.7P-6.6K). Cone-tainers were mowed 0.5 inches four times weekly with clipping removal.

Data collection was identical in year one and year two. Turfgrass quality ratings were recorded weekly based on color, density, texture and uniformity of the bermudagrass surface. Quality was visually evaluated from 1 to 9 — 1 = brown, dead turf; 6 = minimal acceptable turf; 9 = ideal green, healthy turf.