May Begins: Growth Potential, Yellow Patch Again?, Wild Violet, Seed For Fall Divot Recovery

May began and it couldn’t have happened soon enough. A frost is in the air until about May. Not unexpected. However, a slow start can be especially frustrating if you are a grower because there’s going to be a turfgrass area or two in need of recovery from the previous year. Creeping bentgrass just wasn’t doing much (growth) in the upper Midwest. Here is some of what I have been hearing lately — it wasn’t just us dealing with lethargic turf.

Figure 1. Weather conditions from mid-April onward resulted in a cool down (avg soil temperatures fell below 55 degrees) that slowed turfgrass growth. In May a warmer forecast is in store. Bob Berry Sunshine Course, Lemont, IL

To the north in Canada: “Yes it has been a slow start in my area as well. We had a freak weekend of summer back in early April and ever since it’s been below seasonal temperatures and this week is cold and wet! Not the best start for the golf season.” To the south in Atlanta, Georgia: “Just because turf is green does not mean that it is growing, warm season grasses like we have on all playing surfaces at Rivermont needs heat to grow. How much growth is possible is relative to the amount of heat and that is what is referred to as growth potential.” Sounds familiar doesn’t it? In May, we will now cross minimum thresholds necessary for turfgrass growth. Do you hear that sound? Yes, bentgrass is growing again. For the good of the game!

Growth Potential Values for Warm Season and Cool Season Turf

One way of looking at turfgrass growth is by calculating the obvious. Both warm season or C4 (bermudgrass and zoysiagrass) and cool season or C3 (bentgrasses, bluegrasses, fescues, ryegrasses) turfgrasses are going to have a minimum as well as an optimum temperature for growth.

Figure 1. A simple graph showing optimal temperatures for growth of cool and warm season turfgrass. Copyright 2014, PACE Turfgrass Research Institute, www.paceturf.or

Below Cool Season Turfgrass Growth Potential. Below the minimum temperature needed you won’t see much growth for either cool- or warm-season turfgrass = what Chicago just experienced in April.

Above Cool Season Turfgrass Growth Potential. Above optimal temperatures (midsummer) you may see a reduction in growth for cool-season turfgrass = like July in Wichita, Kansas (where I grew up).

Figure 2. Percent warm season and cool season turfgrass growth potential (GP) in selected U.S. locations. Months with 50% or more warm season turf growth potential are highlighted in red, while months with 50% or more cool season turf growth potential are highlighted in blue. Growth potentials are based on 30-year normal average monthly air temperatures obtained from the National Oceanic and Atmospheric Administration (NOAA). Copyright 2005, PACE Turfgrass Research Institute, www.paceturf.org

Yellow Patch of Creeping Bentgrass, Rhizoctonia cerealis

In Chicago, we had seen this disease appear about a month earlier. It was triggered by rainy, foggy, wet weather that occurred the last week of March. In other words a cool-temperature fungal disease, active at 50–65 degrees, that once again appeared in creeping bentgrass surfaces. Generally not a problematic disease because: 1) This Rhizoctonia causes limited damage and, 2) the window of its spring occurrence is brief/transient.

Take home message. The end of April was cold. Yellow patch was a result.

Image 1. Symptoms of yellow patch in a creeping bentgrass/Poa annua golf green. Brian Mores, Inverness Golf Club, Apr 30, 2023

Image 2. Closeup of yellow patch in a creeping bentgrass/Poa annua golf green. Note: Though noticable, the actual damage (usually localized to “smoke rings” ) caused by this Rhizoctonia fungal disease is minimal. Brian Mores, Inverness Golf Club, Apr 30, 2023

Weed of the Week — Wild Violet, Viola species

The right plant in the wrong place? More information on this common Midwestern broadleaf weed comes from Purdue University by Turf Tips / Dr. Aaron Patton et al. Click here.

Friend or Foe? “Collectively, turf managers refer to the Midwest species common blue violet (Viola sororia), wooly blue violet (Viola papilionacea), and confederate violet (Viola sororia f. priceana) all as wild violet. Additionally, yellow violet (Viola pubescens) is also found in Indiana. Wild violets are a persistent, perennial, and difficult-to-control broadleaf plant. It is regarded as a desirable perennial plant by some as well as a weed by others.”

Cultural Practices. “Proper mowing, fertilization, and irrigation can be manipulated to control some weed species but these practices have little impact on wild violet populations in lawns. Wild violet can be decreased by more frequent mowing but not by fertilization. It is unknown how irrigation, drainage, and soil compaction influence wild violet populations. As such, turf managers rely on herbicides to control wild violet.

You Want Some More? If you wish to increase wild violets in your lawn, simply reduce your lawns nitrogen fertilization and maintain moderate to high levels of shade by withholding pruning of trees.

Image 1. Wild violet in full bloom in a Kentucky bluegrass lawn, Evanston, IL. Settle, Apr 30, 2023

Image 2. Wild violet is easy to identify with its characteristic heart-shaped leaf and flowers in the spring. Flower color which can range from white to violet (its common name!). Settle, Apr 30, 2023

Divot Study Update by Shehbaz Singh, MS

In March, 2023 data collection has once again begun for tees used for divot repair research on Bob Berry Sunshine Course, Lemont, IL.

Creeping Bentgrass Trial. Divots that were made in the fall on Sep 7, 2022. Divot mixes without seed in it were unable to recover at least 50% during the 14 week (3 month) time period in the fall. Divot mixes with seed were able to reach that threshold before data collection was halted prior to winter on Dec 7, 2022.

Results 2023. On May 4, 2023, it is almost 8 months since divot creation. Divot mixes without seed remain without 50% recovery or acceptable visual quality. Recovery has begun, but at very slow rate. In contrastdivot mixes with seed in it are now showing at least 80% recovery.

Figure 1. Creeping Bentgrass Fall Divot Trial: Data collection in 2022 (3 months) versus that of 2023 (8 months), Bob Berry Sunshine Course, Lemont, IL.

Figure 2. Creeping Bentgrass Fall Divot Trial: In the spring, treatments without seed (sand) showed less than 50 % divot recovery. While treatments with creeping bentgrass or chewings fescue seed had more than 50% divot recovery on most rating dates, Bob Berry Sunshine Course, Lemont, IL.

Figure 3. Creeping Bentgrass Fall Divot Trial: In the spring, treatments without seed (compost) showed less than 50 % divot recovery. While treatments with creeping bentgrass or chewings fescue seed had more than 50% divot recovery on most rating dates, Bob Berry Sunshine Course, Lemont, IL.

Figure 4. Creeping Bentgrass Fall Divot Trial: In the spring, treatments without seed (8–1–1 mix) showed less than 50 % divot recovery. While treatments with creeping bentgrass or chewings fescue seed had more than 50% divot recovery on most rating dates, Bob Berry Sunshine Course, Lemont, IL.

Figure 5. Creeping Bentgrass Fall Divot Trial: Images taken on Dec 7, 2022 (upper) after 14 weeks/almost 3 months and images taken on May 4, 2023 (lower) after 8 months of divot recovery, Bob Berry Sunshine Course, Lemont, IL. Photos by S. Singh

Conclusion. Fall divots can take a very long time to recover because conditions for turfgrass growth are ending and will not return until sometime the following year (May in most years). If seed is used in a divot mix, it will help expedite divot recovery by turfgrass — especially during the fall season.

Final Photo

Lilac History via Wikipedia. Both S. vulgaris and S. × persica the finer, smaller “Persian lilac”, now considered a natural hybrid — were introduced into northern European gardens at the end of the 16th century, from Ottoman gardens. The Holy Roman Emperor’s ambassador, Ogier Ghiselin de Busbecq, is generally credited with supplying lilac slips to Carolus Clusius, about 1562. Well-connected botanists, such as the great herbalist John Gerard, soon had the rarity in their gardens: Gerard noted that he had lilacs growing “in very great plenty” in 1597, but lilacs were not mentioned by Shakespeare. Photo: Evanston, IL. Settle, Apr 30, 2023