Nutsedge News

Nutsedge: The Superweed


The best way to describe nutsedge is “superweed.” Unlike other broadleaf weeds, this sedge has a robust root system made of nut-like tubers called nutlets. The nutlet stores a high amount of energy for the nutsedge to use in its lifecycle. With their grass-like leaves, sedges can be difficult to distinguish within the lawn at the beginning of the growing season. In the hot, humid, sunny days of summer, however, it grows faster than most grasses and even begins to flower. It is easy to distinguish only a few days after mowing by the lighter green leaves shooting up quicker and taller than the grass surrounding it.

Because of its reliance on heat and light, nutsedge does not do well in shady areas. Nutsedge thrives particularly well in wet soil and will invade areas where it didn’t grow in the past because of the amount of moisture retained in the soil. Increased soil moisture could be from poor drainage, too much rain or irrigation, or even water run-off from a leaking hose. If any of these things can be modified, that might help. Otherwise, a fall aeration may be necessary to relieve soil compaction, which will aid in better overall drainage.


How to Treat It

In the lawn and landscape industry, nutsedge continues to be an issue we tackle head-on. Unlike annual grassy weeds like crabgrass, we have no pre-emergent herbicides that allow us to treat the sedge before it sprouts. Instead, we can only treat nutsedge post-emergently while we can see it. Because of the stored energy in the “superweed” nutlets, it is not uncommon for nutsedge to recover after we treat it and reappear after only a couple of weeks. Even hand-pulling is only partially effective unless you remove the entire root system.

It often takes several herbicide applications entirely control this tenacious weed until it dies off in the cooler fall temperatures. Even then, there still might be enough stored energy in the roots for it to return the next year. While we are happy to treat the nutsedge when we find it in the yard, or when we receive a service request, there may be circumstances where further treatment is no longer advisable. If herbicide could burn the lawn due to heat or drought, we recommend postponing chemical treatment to prevent damage.


For your reference, consider reviewing the links below for additional information:

Too Late for Crabgrass? When is the best time to treat?

The best way to control crabgrass is to kill it before it grows with a pre-emergent herbicide, but when is it too late to treat? Unfortunately, there’s no single definitive answer to this question. The short answer is to apply it before the crabgrass has a chance to germinate. The longer answer is that it depends on the weather and which pre-emergent is being used. Pre-emergent herbicides work by creating a chemical barrier that kills the crabgrass when it germinates. Some pre-emergent products provide some post-emergent control as well. Determining when a seed germinates depends on many variables in the environment. For crabgrass, the biggest variable is temperature. Crabgrass only germinates at sustained soil temperatures above 57°F at a one-inch depth. The best way to track the soil temperature is with growing degree days (GDD). Because it is tough to track soil temperatures without specialized equipment, we can use air temperature. Air temperatures will usually need to be at around 50°F for 200 degree days for germination.

200 days! That sure seems like a long time! That’s a common misconception that sometimes even confuses our office staff, but GDD isn’t just based on a calendar. GDD is based on a formula calculated by monitoring the median temperature. When the median temperature (High plus low divided by 2) for a day is above the range needed for germination, the number of degrees above that point is added to the GDD. For example, if the air temperature is at 52°F one day, 53°F the next day, and 49°F the day after that we have 5 GDD for that time period (there’s no such thing as negative degree days because plants can’t un-grow). It’s important to remember that areas in full sun or next to pavement will be warmer, and areas in the shade will be cooler than the average, so you have to take that into account with your own lawn.

Crabgrass Growing Degree Days Formula
(GDD Formula1)

All this math is a major pain just to find out if it’s too late to apply your pre-emergent crabgrass control. The rule of thumb that many landscape professionals used to go by was when the forsythia starts blooming. These days we have meteorologists help us out. To track the GDD yourself go to and follow these steps2:

  1. Enter your zip code (not all locations are included, check nearest weather station to your site) and hit enter
  2. Click the “custom” tab/button below the date
  3. Enter the start date below the word “from” (ex. Jan. 1) and the end date below the word “to” (current date)
  4. Hit the get “history” button
  5. Read your growing degree days (base 50) in the ‘Sum’ column (=Cummulatlive DD to date for the year)

Of course, the easiest way to make sure your pre-emergent crabgrass control gets applied on time is to call MRW Lawns at 301-870-3411 and let us take the work and worry out of having a real wonderful lawn.




P.S. If the growing degree days are over 200 in your area, don’t panic! There are post-emergent products that can help control crabgrass, even when fully grown; and in the worst-case scenario, crabgrass is an annual weed, so you’ll get another crack at it next year!

Know your lawn weeds-Common Weeds in Maryland

Often, clients will call concerned with what they perceive as weeds in their lawn. Our regular applications control most of the weeds in your lawn, but there are a few that require special applications. This publication from the Home and Garden Center Information Center of University of Maryland Extension explains the basics of lawn weed biology and how they are controlled. There are two exceptions to the article that I would like to make you aware of. (more…)