Kentucky bluegrass goes dormant by allowing its leaves to die but keeping the crown (the origin of new roots and shoots) alive. It needs only minuscule amounts of water to survive. Also, Kentucky bluegrass can generate new roots and shoots from its rhizomes (a feature lacking in most other common lawn grasses).
Healthy dormant Kentucky bluegrass (low traffic) vs. Dormant Kentucky bluegrass under high traffic. Try to keep your lawn like the one on the left!
Southern Wisconsin has had a prolonged period of very hot and dry conditions. Many parts of the state have seen little or no rain in at least 30 days. Kentucky bluegrass is the dominant species of grass growing on Wisconsin’s lawns. Fortunately, it is extremely tolerant of these conditions and can survive periods up to and even beyond 60 days without water. Kentucky bluegrass survives by allowing its leaves to die, but keeping its “crown” alive. The crown is the tiny part of the plant where the grass blades meet the roots. It is so small, that it requires only a minute quantity of water to survive. However, at some point, it too will die. Fine fescue and perennial ryegrass are fairly common components of lawn seed mixtures. While fine fescue can survive the drought as well or better than Kentucky bluegrass, perennial ryegrasses are probably near death. The good news is that our winters usually kill perennial ryegrass, so most lawns don’t have large populations of it.
How much longer can my lawn survive?
First, to lengthen the time your lawn can survive without water, don’t apply any fertilizers, herbicides, or other chemicals to your lawn. Other than the types of grass in your lawn and how you manage it, many variables affect how long your lawn can survive without water. Grasses that receive foot or vehicular traffic are much less tolerant of dry conditions. Lawns grown on compacted soils will require more attention than those on healthy soils. Similarly, high clay or sand content soils cannot support drought stressed lawns as long as loamy or silty soils. If your lawn falls into any of these categories, I recommend watering it soon, following the guidelines below.
How much and when to water?
Healthy green grass uses about one inch of water each week. However, when your turf is brown, it uses much less. In fact, you only need to apply about one quarter of an inch per week (or about a half inch every other week) to keep the crowns hydrated, and ensure that your grass will green up when the rain begins. It is not a good idea to apply much more than this amount, as the turf will start to send out new green leaves which will require lots of water to maintain their greenness. Water at night or early morning, when peak demand it lowest, and evaporative losses are least likely.
Is there a way to check to see if my lawn is still alive?
Unfortunately, it is quite difficult to tell if the crown is still alive simply by looking at it. However, some clues that your plant is doing fine is any semblance of white tissue around the crown (you’ll have to peel back most of the leaf sheaths and pick off some roots. Another good sign that the grass is alive is green tissue like that shown in the leaf blades in the picture below. Also, it is a good sign if the roots are firmly attached to the crown and difficult to detach by pulling.
Now that nobody is thinking about snow mold, the 2012 UW Snow Mold Reports have been posted online at the Turfgrass Diagnostic Lab’s website in the ‘News’ section on the righthand side (http://www.tdl.wisc.edu/). Reports and pictures from 2 sites in Wisconsin, 1 site in Michigan’s UP, and 2 sites in Minnesota have all been posted. Unfortunately, the mild winter led to acceptable snow mold results being obtained only from the Wawonowin site. The reports will also be permanently housed on the TDL’s ‘Research’ page.
Special thanks to Brian Horgan and Andy Hollman for their help with the Minnesota sites, and also to the following superintendents for hosting both our snow mold trials and other winter research:
- Antigo Bass Lake – Dave Van Auken
- The Legacy at Craguns – Matt McKinnon
- Les Bolstad GC- Brent Belanger
- Odana Hills GC- Jeff Jushka
- Sentryworld GC – Gary Tanko
- Wawonowin CC – Andy Hakkarinen
Please call or email with any questions, concerns, or comments you may have regarding these reports.
Check out the two pictures below. The one one the left shows a strip of perennial ryegrass infested with dandelions, but the surrounding tall fescue is dandelion free. The p. rye and t. fescue were planted at the same time and have been managed identically for the past five years. The picture on the right is of a stand of Kentucky bluegrass (left side of picture) next to a stand of tall fescue (on the right). While the effect is less dramatic, it’s clear that the left side has dandelions while the right side does not. I’ve also noticed this effect in my tall fescue lawn – my neighbors have dandelions and I don’t. But I do have plenty of clover, which also has infested the tall fescue in the pictures below.
Yesterday, I asked Paul Koch (TDL Manager) how the soil temperatures may influence timing for control of our early season patch diseases. Here’s what he said (from vacation, nonetheless):
“Though soil temps are in many cases indicating that initial fungicide applications for important diseases such as summer patch, take all patch, and fairy ring should be applied soon I would recommend holding off unless there is recent history of significant infection at the site. The primary reason for this is the time required for both the plant to begin growing (and exude chemical signals to the fungi) and for the fungus to respond and begin growing and responding to the signals. The fungi have certainly begun responding, but now that temperatures have moderated any growth or infection by the fungi has likely dropped considerably. If a fungicide application has already been made, be prepared to make additional applications in the coming months.”
How amazing is it to see the soil temperatures go from frozen on March 7th to over 50 degrees on March 16? We sustained temperatures above 50 for 10 days, and have now dropped below 50 degrees at two inches. Crabgrass germinates when soil temperatures are around 60 degrees. The soil temperatures from the Noer are taken under a dense Kentucky bluegrass lawn, but in areas where crabgrass is normally problematic (bare soil, near concrete, etc.), the temperatures were probably 2-5 degrees warmer – enough to start the germination process.
So how will this up and down roller coaster of soil temperatures affect crabgrass pressure in Wisconsin? I wish I knew. Crabgrass may have germinated in some areas, but may not have in others. An herbicide with both pre- and post-emergent activity will be the safest bet in these uncharted waters.
Well, I took a guess on my last post that the GDDs were going to be off this year. For Southern WI, at least, I’d like to retract that. The picture below shows the Forsythia right outside my office in full bloom, with soil temps around 55 F and the GDD model says we are in prime time for crabgrass prevention – so all is well there. The 15 day forecast shows highs in the 70s all this week, and then dropping to the 60s and 50s for next week. These temperatures will not put a damper on the current green-up and bloom. That puts us into April, where cold temperatures are not likely to linger very long if they even show up. I’m not sure what’s going on in Northern WI, but it looks like Southern WI will have an entire month longer growing season this year.
It’s not even St. Patty’s day and the growing degree day models are starting to light up all over Southern Wisconsin. Because the season has been so unseasonably warm, many have been asking about the accuracy of the models. I don’t know for sure, but I’ll take a guess and say that I think they are going to be off this year in many places.
Growing degree days are a simple way to estimate the progression of the season, similar to but much easier than tracking soil temperatures. Growing degree days don’t start accumulating until the average temperatures get above freezing (sometimes above 50F). Normally this coincides with when the snow and frost leave. However, due to the quick onset of really warm temperatures, many places may still have had frost in the ground when the growing degree days were skyrocketing. In these situations, the models will be ahead of reality, in situations where the frost was out before the warm streak, the models may be pretty accurate. Either way, I recommend erring on the upper end of the target ranges this year. Also, for the Primo/Proxy users, I recommend going with split applications this year. Check out the USGA research article on our Primo/Proxy GDD page by Randy Kane and Lee Miller for application ideas.
One way to check how the models correlate to soil temperatures is to measure soil moisture and pay attention to the crabgrass pre-emergent GDD model. The optimum timing for applying crabgrass pre-emergent herbicide is when soil temperatures are 50-55 F. The optimum growing degree days for pre-emergent application is 250-500 GDD. So if soil temperatures (two inch) are 50-55 degrees F when the model is between 250 and 500 GDD, I’d say things are on track. However if soil temperatures are still delayed significantly when we hit 350 GDD, then you can bet that the GDD models for the rest of the year will be off.