Naturalized Grass Stands for Golf Courses

Some reasons for this relate to aesthetics and golf course design, whereas others center on reducing labor and resources. At certain times of the growing season, brown wispy seedheads of non-mowed grasses impart a natural look to the course, reminiscent of the classic links courses in coastal areas of the British Isles. Naturalized grass stands can also serve as hazards, offering challenges for golfers and penalties for errant shots.

From the manager's point of view, naturalized grass stands serve the practical purpose of reducing costs associated with water, fertilizer, fungicides, and mowing. With budget reductions and labor shortages plaguing golf course operations across Pennsylvania, it is not surprising that more areas are being converted to naturalized grass stands on golf course properties.

Naturalized grass stands can also be a maintenance challenge for golf course managers. These areas often become infested with weeds, insects, and burrowing animals. Because of the nutrient-rich soils throughout much of Pennsylvania, perennial grasses grow rapidly, and stands become extremely dense. Hence, occasional mowing, thinning, and removal of stem and leaf debris may be needed to keep naturalized grass stands in good condition. Mowing and thinning operations often require specialized equipment, adding capital expenses to the budgets of some golf course operations.

The next few paragraphs provide a brief overview of the species, placement, mowing regimes, and weed problems of naturalized grass stands on Pennsylvania golf courses.

Species Selection and Establishment

In the Northeast and Mid-Atlantic regions of the U.S., the fine fescues and tall fescue are the most persistent and aesthetically acceptable grass species for naturalized areas on golf courses. Of the fine fescues, hard, sheep, and Chewings are most popular in mixtures used for establishing naturalized stands. Although creeping red fescue performs well in most regions of Pennsylvania, and is an excellent grass for weed suppression, it tends to become very dense and not conducive to finding or striking golf balls. Although creeping red fescue seed is present in some fine fescue seed mixtures, it is usually less than 40% by weight. By itself, creeping red fescue is best placed in areas furthest from active play.

Hard and sheep fescues are relatively heat, drought, and shade-tolerant when grown in non-mowed stands. The foliage of hard fescue is typically dark green, whereas sheep fescue foliage has a blue-green hue. Hard and sheep fescues are somewhat slower to establish than Chewings and creeping red fescue. However, they can make vigorous, and sometimes excessive, growth in fertile soils. Although hard fescue performs well in Southeastern Pennsylvania, trials in central Pennsylvania have shown occasional thinning and decline of some hard fescue cultivars in early spring following late fall mowing and cold winter temperatures.

Chewings fescue cultivars have lighter green foliage than hard fescue and produce attractive light brown seedheads. This species grows well in most areas of Pennsylvania and, like creeping red fescue, can become quite dense in fertile soils. Chewings fescue is a common component of seed mixtures used for naturalized grass stands; typically, between 20 and 40% of the seed mixture based on seed weight.

Generally, there is little advantage in mixing other grass species with fine fescues in naturalized grass stands; however, one species native to North America, little bluestem, has performed quite well in trials conducted at Penn State when mixed with fine fescue at low seeding rates (10 to 20 pounds of little bluestem seed per acre). This species grows taller than fine fescues and produces an attractive red color in late summer and fall.

Tall fescue is less popular as a species for naturalized grass stands due to its coarse texture and the fact that golfers find it difficult to play from when dominant in infrequently mowed stands. However, this species is persistent, heat- and drought-tolerant, and competitive with invasive weeds. Tall fescue also produces aesthetically pleasing seedheads when viewed from a distance.

Although there are different ways of establishing fine fescues, research at Penn State's University Park campus and Longwood Gardens in Kennett Square, Pennsylvania has demonstrated successful establishment when the entire site is treated with glyphosate, core aerated, and sliced prior to slit or broadcast seeding. Establishment from seed is generally more successful when performed in late summer versus spring, as there is less competition from weeds and the grass has two cool growing seasons to become established before being subjected to summer heat and drought stress. Seeding rates of fine fescues vary, but research trials in University Park show that 4 pounds per 1000 sq ft provides a vigorous stand that is competitive with weeds. Starter fertilizer will help speed establishment, but once grass covers the soil surface, fertilization should be curtailed. Some golf course renovation projects have used fine fescue sod as a means of establishing naturalized grass areas. Although more expensive than seeding, this method offers the advantage of establishing fine fescue quickly with little to no weed competition.

Location

Location is a key consideration in using naturalized grass stands on golf courses. Infrequently mowed grasses located near irrigation heads will often lodge due to water accumulation on seedheads and become unsightly. Areas with tall grasses too close to fairways and greens are subject to lost balls and difficulty in striking the ball accurately, thus slowing play. Fine fescues are not particularly wear tolerant and should be kept away from areas with high cart and foot traffic. To avoid these issues, naturalized grass stands are usually kept away from irrigation heads and in out-of-play areas behind bunkers and primary rough.

Other areas that are a good fit for naturalized grass stands include steep banks that are difficult to mow, low-traffic areas around tees, near wooded areas, buffer strips along ditches and stream banks, soil mounds serving as barriers between the golf course and roads, and in large swaths of open land not in play. Features such as stone walls and split-rail fences can be enhanced by careful placement of non-mowed fine fescues.

Areas of the course with poorly drained soil and/or that remain wet for long periods can be good candidates for naturalized areas, but may require species that are better adapted to these conditions than fine fescues. Areas intended to attract birds and other wildlife may be better left to more diverse plantings, including some shrubs and small trees that provide cover and food.

Mowing

Periodic mowing can improve aesthetics of naturalized grass stands, suppress certain weed species, as well as help with thinning. To keep naturalized areas in grass and reduce encroachment of trees and shrubs, the areas must be mowed at least once per year. Many, if not most, naturalized grass stands in Pennsylvania are mowed only once per year in late fall. Golf course operations with adequate labor and equipment may mow two or three times per year. The timing and frequency of mowing vary depending on the experience of the manager and the effect desired, but early to mid-spring, after seedheads dissipate in late summer, and when the golfing season ends in fall are most popular. Mowing after lodging occurs following heavy summer rainstorms can improve the appearance of the stand and prevent smothering of tillers beneath the fallen stems.

Mowing of tall grass plants requires specialized mowers and attachments, as well as equipment for the removal of stem and leaf debris. Mowing equipment used on golf courses in Pennsylvania includes adjustable height rotary mower decks attached to tractors, flail mowers, and, in some cases, hay cutting equipment rented or borrowed from local farmers. When mowing does occur, cutting heights should be about 4-6 inches.

Collecting and removing cut stem and leaf material makes for a neat appearance of the stand and reduces smothering of new shoots emerging in spring. Units that can collect and dump leaf and stem material are the most efficient means of removing debris from naturalized grass areas. On steep slopes, the collection of leaf and stem debris may have to be performed by hand.

Weed Management Considerations

Perhaps the most challenging aspect of managing naturalized grass stands is keeping weed populations to an acceptable level. Encroachment of different plant species is part of the natural succession of an infrequently mowed grass stand, and keeping all invaders out is unrealistic. Some golf course managers let nature take its course in these areas and do not devote a lot of effort to controlling weeds. Many other managers attempt to control some of the most invasive and objectionable weed species in infrequently mowed grass stands.

Deciding which species should be controlled or suppressed, and which species can be left alone, depends on the expectations of golfers and the judgment of the manager. Some weeds, such as milkweed, butterfly weed, aster, and Queen Anne's lace, may be desirable when present in small populations, as they enhance the appearance of the stand, attract pollinators and butterflies, but do not interfere much with play. Other weeds, including Canada thistle, quackgrass, Japanese stiltgrass, nutsedge, and foxtail, are more aggressive and can spread rapidly, taking over large portions of the stand. Thus, managers need to determine which weeds are problematic and then decide what, if anything, to do about them.

Many annual grass and broadleaf weeds can be controlled or suppressed with preemergence herbicides. If no spring seeding will take place, products containing pendimethalin, prodiamine, and other preemergence active ingredients can be used for control of crabgrass, goosegrass, and foxtail. Isoxaben can be used for controlling some annual broadleaf weeds.

Control of perennial grasses, sedges, and broadleaf weeds can be challenging in infrequently mowed fine fescue stands. If only a few single-stalk weeds are present, such as horseweed or Canada thistle, they can be removed by hand or with string trimmers. However, postemergence herbicides are usually more efficient for reducing extensive weed infestations. Some postemergence herbicides will injure fine fescues, whereas others are relatively safe, so be sure to read product labels carefully for tolerant species before using in naturalized grass areas.

Two postemergence grass herbicides that are effective in controlling annual and perennial grass weeds in infrequently mowed grass stands are fluazifop-P-butyl (Fusilade II Turf & Ornamental Herbicide or Ornamec 170) and sethoxydim (Segment II or Sethoxydim SPC). Both herbicides are safe to use on fine fescues at label-specified rates, but differ somewhat in the species of weed grasses controlled. Caution should be exercised when using these herbicides near native grasses, such as little bluestem and switchgrass.

Yellow nutsedge can be controlled postemergence with one of several different herbicides that contain sulfentrazone (Dismiss, Dismiss NXT, Solitare, or Echelon 4SC), halosulfuron (Sedgehammer or Prosedge), or Imazosulfuron (Celero). Nutsedge herbicides are best applied in mid-June before tubers (nutlets) mature.

Highly invasive broadleaf weeds can be controlled by one or more combinations of broadleaf herbicide active ingredients. One of the most tenacious and common broadleaf weeds, Canada thistle, can be controlled with postemergence applications of clopyralid-containing products such as Confront or Lontrel. Canada thistle has extensive rhizomes and is a prolific seed producer; thus, it has the potential to produce new plants throughout the growing season. Follow-up herbicide applications are often needed for acceptable control of this weed species.

Summary

Naturalized grass stands can enhance the beauty of golf courses and create interest and challenges for golfers. The selection of fine fescue seed mixtures and seeding at the correct time of year are paramount in a successful establishment. Infrequently mowed grass stands should be placed in areas that do not receive irrigation or fertilizer, and where play will not be slowed. Mowing should occur at least once per year, and possibly more frequently, to suppress weeds, shrubs, and tree growth. Weed management is a significant challenge in maintaining naturalized grass areas, and managers should devise a plan for troublesome weeds and scrutinize herbicide labels for safety to fine fescues and efficacy on target weeds.

Prepared by Peter Landschoot, Professor of Turfgrass Science. The author acknowledges the following individuals and organizations for providing assistance in research studies on naturalized grass areas: Shawn Kister, Longwood Gardens; Tom Bettle and Bill Meyers, J. Valentine Turfgrass Research Center, Penn State; Matt Anasiewicz, Helena; Mark Leppert, Sunnehanna Country Club; Jeff Gregos, E.H. Griffith; and The Pennsylvania Turfgrass Council.