April Wrap-Up! Poa Seedheads, Temperature Swings, and CDGA Topdressing Research
As April draws to a close, spring is making its presence known across the turf. Poa annua is actively growing and producing seedheads — one of the most visible indicators of spring progression on golf courses. Creeping bentgrass is slowly picking up growth, and additional varieties in the CDGA trial plots are now displaying vibrant green hues. Notably, growth around aerification sites confirms that cool-season turf is beginning to respond favorably but slowly to rising soil temperatures. Warm-season grasses at Bob Berry Sunshine Course in Lemont are also beginning to react: Zoysiagrass is showing subtle signs of green-up, while Bermudagrass remains largely dormant, still requiring sustained warmth to break full dormancy.
The final week of April brought sharp and unpredictable swings in air temperature, with daytime highs peaking above 80°F and dropping into the 50s just days later — characteristic of early spring in the Midwest. Soil temperatures mirrored this fluctuation, hovering in the mid-50s to low 60s throughout the week. However, they have now reached the critical 60°F threshold that supports more uniform turfgrass growth and microbial activity in the root zone.Alongside turf development comes increased pest activity; annual bluegrass weevil (ABW) adults have been observed across Chicago-area golf courses, marking the start of their spring emergence. Finally, the arrival of dandelions in full bloom is another classic spring visual indication, adding bursts of yellow across roughs, while also reminding superintendents of the need for continued weed monitoring and management.
Annual Bluegrass (Poa Annua) Seedheads
Poa annua seedheads have begun to emerge across the golf course turf. However, the peak seedhead production can be observed in the next week or so. This cool-season annual grass is known for producing prolific seedheads in the spring, which can disrupt playing surfaces and mowing quality. Their appearance also serves as a biological marker for timing key golf course management practices, such as plant growth regulator applications aimed at suppressing seedhead formation and maintaining smoother greens. Growing Degree Day (GDD) tracking is a valuable tool for predicting the emergence of Poa annua seedheads, helping golf course superintendents time applications of plant growth regulators (PGRs) for optimal suppression.
GDD Tracker 4.0 — Turf Pest Management Tracking and Alerts
Evaluating Newer Alternative Topdressing Materials (Angular Sands) for Their Effects on the Playability of Putting Greens
A new CDGA bluecoat turfgrass research study is being conducted on Green 1 (‘Pure Distinction’ creeping bentgrass) at Bob Berry Sunshine Course in Lemont, IL.
Frequent sand topdressing is a common cultural management practice in routine golf course maintenance. Regular sand topdressing helps to ensure a smooth green surface, and this enhances playability. Regular sand topdressing also prevents excessive thatch and organic matter accumulation. Traditionally, subangular sand is used for topdressing sand. More recently, superintendents have begun using angular sands with a coarser particle size (similar to bunker sand) for regular topdressing to improve surface characteristics of putting greens. Also, biochar, an organic matter alternative, is being used in topdressing sand as well as root zone mixes. Scientific research is needed to validate the effects of newer alternative topdressing materials.
Objective
- Evaluate creeping bentgrass growth and surface playability characteristics of a putting green surface given subangular versus angular topdressing sand.
- Evaluate turf health with and without biochar in topdressing sand.
Materials and Methods
- The study is being conducted using a randomized complete block design with 4 replications of five treatments.
- Individual plots were large and measured 10 ft x 10 ft.
- Two types of calcareous sand materials were used.
- Angular Sand: Diamond Bunker Sand, Thelen Materials, Antioch, IL
- Subangular Sand: 2340 High CU Topdressing Sand, Waupaca Sand & Solutions, Waupaca, WI
- Sand was uniformly applied on individual plots using a Scotts Turf Builder 22-inch W Drop Push Spreader (Scotts Miracle-Gro, Marysville, OH).
- Biochar was uniformly spread by hand before topdressing sand was applied.
Data Collection
- Visual Turf Quality: 1 to 9 scale, 9 = best and 6 = minimum acceptable quality
- Normalized Difference Vegetation Index: GreenSeeker handheld sensor (Trimble Inc., Westminster, CO).
- Ball Roll (ft): USGA stimpmeter
- Surface Firmness (in.): TruFirm (Spectrum Technologies, Aurora, IL).
- Shear Strength (Nm): Shear strength tester, (Turf-Tech International, FL).
- Root Length (in.): Maximum root length using 0.5-inch diameter soil sampler
- Thatch Depth (in.): Thatch depth using 0.5-inch diameter soil sampler
- Matt Layer Depth (in.): Measured a 0.5-inch diameter soil sample
- Root Feeding Nematodes (nematodes per 100 g soil): Modified sucrose flotation technique with centrifugation
Visual Quality — 2024
- No differences except on Aug 7.
- Aug 7, Angular sand + biochar had a higher visual quality than subangular sand and untreated.
- Compared to untreated, all sand topdressing treatments appeared visually greener on Oct 16.
Surface Firmness — 2024
Surface firmness is measured as TruFirm depth (in inches). A greater TruFirm depth indicates a softer surface (less firmness), while a smaller TruFirm depth indicates a firmer surface.
- All sand topdressing treatments were significantly firmer than the untreated on Aug 22, Sep 5, and Oct 16.
- Area Under Progress curve — Surface Firmness (AUPC): Subangular Sand provided a firmer surface compared to angular sand and untreated in 2024.
- Overall, the least firm surface was observed on Aug 22 due to high average soil moisture content
Thatch Depth
- Thatch depth was reduced in all sand topdressing treatments versus the untreated.
More information about the topdressing sand study is available on the CDGA Turfgrass Program website under the ‘Ongoing Research’ section.
Final Photo
Quercus macrocarpa, the bur oak or burr oak, is a species of oak tree native to eastern North America. It is in the white oak section, Quercus sect. Quercus, and is also called mossycup oak, mossycup white oak, blue oak, or scrub oak. The acorns are the largest of any North American oak (thus the species name macrocarpa, from Ancient Greek μακρός makrós “large” and καρπός karpós “fruit”), and are important food for wildlife. See Wikipedia
