USGA Update - May 2013

Why Are Our Greens So Bumpy?

By David A. Oatis, director, Northeast Region
May 15, 2013


Cool, dry weather has been the norm throughout most of the Northeast Region, but the recent series of storms brought much needed rainfall. Temperatures, however, remain cool, and much of the region is 1-2 weeks behind normal. Grasses all react a little differently during the periods of seasonal transition. Kentucky bluegrass is slow to green up in the spring, whereas perennial ryegrass maintains good color all winter and begins growing much sooner in the spring. When multiple grasses are present, the variation in their growth rates makes for uneven playing surfaces. This is especially apparent on putting greens in the Northeast Region right now. Greens are bumpy, and they won’t get smooth until the temperatures warm up.

Most golfers think of putting greens in a “singular” sense, but each putting green is comprised of millions of individual plants. In the northeast, most greens are populated by two species: annual bluegrass (Poa annua) and creeping bentgrass, but there are many biotypes of each. In general, bentgrass initiates growth first in the spring, but it grows very slowly. Once temperatures warm a little, annual bluegrass kicks into high gear, and its growth rate outpaces creeping bentgrass. To further complicate matter, the different biotypes can vary significantly. This is the stage many courses are entering right now. In short, the different grasses all are growing at different rates, and this makes putting greens bumpy! Add annual bluegrass seed heads to a surface and the recipe is perfect for questions and complaints.

Bentgrass at many courses remains off color, and it is very susceptible to mechanical injury during periods of cool weather each spring. The lack of growth, poor color and susceptibility to mechanical injury often is attributed to a disease. This phenomenon occurs nearly every spring to some extent, but it is much worse when the period of temperature fluctuation is longer. Two or three days or more of warm temperatures are usually sufficient to get bentgrass growing, but when cold nighttime temperatures occur, the bentgrass shuts down again.

So, the grasses are growing at different rates right now, and nothing that can be done to combat it. The best course of action now is to avoid maintenance practices that constantly injure the bentgrass. Aeration, verticutting and topdressing treatments are fine, but repeated treatments of each will cause injury to bentgrass. Even rolling and repeated mowing can cause injury to the bentgrass right now, so if your bentgrass populations are thinning or showing signs of injury, back off on them.

Once temperatures warm sufficiently, bentgrass will begin growing more vigorously, and it will tolerate stressful maintenance practices. However, the yearly decline of annual bluegrass will follow close behind. Once annual bluegrass produces its seed, plants begin to turn yellow and root systems shrink back, so we will begin talking about problems with annual bluegrass then. Since cool weather is predicted to last for a few more days at least, that will probably not happen for a few more weeks.

For now, golfers in the Northeast will have to suffer with bumpy greens. When will they smooth out? Right after the temperatures stay consistently warm! When will that occur? I’ll leave that answer for your favorite weather man!