Going Natural on PA Golf Courses

By Pete Landschoot, Ph.D., Professor of Turfgrass Science, Penn State University

The trend of establishing infrequently mowed grass stands, often referred to as naturalized grass stands or native areas, on Pennsylvania golf courses has been steadily growing over the last two decades. Some reasons for this relate to aesthetics and design, whereas others center on reducing labor and conserving resources. At certain times of the growing season, the 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 (Figure 1).

FIGURE 1: Non-mowed fine fescue on the Ailsa Course at Turnberry; a classic links course built in sandy soils on the southwest coast of Scotland.

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 and the U.S., it is no wonder that more areas are going “natural” on golf course properties.

On the flip side, naturalized grass stands can be a headache for golf course managers. These areas often become infested with weeds, insects, and burrowing animals. Because of the nutrient-rich mineral soils throughout much of Pennsylvania, perennial grasses grow rapidly and stands can become extremely dense. Hence, 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 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 for finding or striking golf balls. Although creeping red fescue is present in some fine fescue 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. 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 (Figure 2).

FIGURE 2: Stand of ‘Marco Polo’ sheep fescue in a partially shaded wooded area.

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 is a common component of seed mixtures for naturalized grass stands (typically between 20 and 40% by weight).

Mixing other grass species with fine fescues in naturalized grass stands is generally discouraged; however, one species native to North America, little bluestem, has performed quite well in our trials when mixed with fine fescue at low seeding rates.

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 non-mowed stands. However, it is persistent, heat and drought tolerant, and competitive with invasive weeds. This species also produces aesthetically pleasing seedheads when viewed from a distance (Figure 3).

FIGURE 3: Non-mowed stand of tall fescue on a golf course in Western Pennsylvania.

Although there are different ways of establishing fine fescues, we have had the most success 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 our research trials show that 4 lb./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. Non-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 (Figure 4).

FIGURE 4: The 10th hole at the Club at Nevillewood in Pittsburgh, demonstrating ideal placement of naturized stands of fine fescues near tees and behind fairway bunkers, well away from primary landing areas.

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 or houses, 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 number and timing of mowing varies depending on the experience of the manager and the effect desired, but early-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 (Figure 5).

FIGURE 5: Lodging of fine fescue naturalized area following heavy rains in July.

Mowing of tall grass plants requires specialized mowers and attachments, as well as equipment for removal of stem and leaf debris. Mowing equipment used on golf courses in Pennsylvania include adjustable height rotary mower decks attached to Ventrac or Steiner 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 pickup, collect, and dump leaf and stem material, such as the Wiedenmann Super 500, are the most efficient means of removing debris from naturalized grass areas. On steep slopes, collection of leaf and stem debris may have to be done 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 a non-mowed grass stand, and keeping all invaders out is unrealistic. In fact, some golf course managers let nature take its course in these areas and don’t devote a lot of effort to controlling weeds. Many other managers attempt to control some of the most invasive and objectionable weed species in non-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 judgement of the manager. Some weeds, such as milkweed, butterfly weed, aster, and Queen Anne’s lace are desirable when present in small populations, as they enhance the appearance of the stand, attract pollinators and butterflies, but don’t 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 it. (Figure 6)

FIGURE 6: Plants like milkweed and aster can add diversity and color to naturalized grass stands.

Many annual grass and broadleaf weeds can be controlled or suppressed with preemergence herbicides. If no spring seeding will take place, products containing pendimethalin, dithiopyr, prodiamine, and other preemergence active ingredients can be used for control of crabgrass, goosegrass, and foxtail. Isoxaben (Gallery 75 DF) can be used for controlling some annual broadleaf weeds.

Control of perennial grasses, sedges, and broadleaf weeds can be challenging in non-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 are fluazifopP-butyl (Fusilade II Turf & Ornamental Herbicide and Ornamec 170) and sethoxydim (Segment II and Sethoxydim SPC). Both herbicides are safe to use on fine fescues at labelspecified rates but differ somewhat in the species of weed grasses controlled. Caution should be used when applying 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 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. Selection of fine fescue seed mixtures and seeding at the correct time of year are paramount in successful establishment. Non-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 herbicides labels for safety to fine fescues and efficacy on target weeds.

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