Yellow Nutsedge Invades My Perfect Tall Fescue Lawn!!

The yellow nutsedge (Cyperus esculentus) took over the tall fescue turf during the night. I am sure of it.  One day it wasn’t there and the next day it was.  It was lurking under the recently sodded tall fescue turf-just waiting for the perfect opportunity to grow through the soil/sod layers and now it has become an embedded part of the lawn…almost uniformly.  It wouldn’t be so bad except that it is much lighter in color than the desired turf species and it grows faster than the tall fescue, making what was a recently mown lawn unsightly in just a few days. 

This isn’t an isolated problem in many tall fescue lawns.  Nutsedge is pretty common in many areas of California.  It is often associated with turfgrass because of the frequent irrigation that many turf species require. 

Because it is a perennial weed, it can be very difficult to manage, particularly if there is a bank of tubers in the soil.  The tubers can survive for up to 3 years in soils and once conditions are suitable, the tubers can begin the growth cycle again.  If you can

reduce or limit tuber growth, then you can limit the nutsedge but it takes persistence by keeping the plants below 5-6 leaves.  Keeping the plant with only a few leaves reduces the plants ability to produce tubers because of a reduced ability to produce and store carbohydrates.  This may mean hand weeding every week all summer to get it under control. This system isn’t really practical for nutsedge established in a turfgrass.  Mowing doesn’t reduce the plant enough to help.  Unfortunately, the only way to really get nutsedge that has invaded a tall fescue lawn under control is through the application of good cultural practices for the turf complimented with post emergent weed control.  This includes proper fertilization in the spring and the fall (avoid summer), and mowing at the correct height.  In spring and fall, you should mow at about 2.5 inches and up to 3.5 inches in the heat of summer.  Higher mowing tends to mask the nutsedge more and also increases the shading effect the turfgrass can have on it. 

In terms of post emergent chemical control, there are only a few post emergent chemicals registered that tall fescue is tolerant of.  That includes:  

• *halosulfuron (available as Sedgehammer or Manage)
•  sulfosulfuron (available as Certainty)  
•  trifloxysulfuron (available as Monument)
• *⁺Penoxulam (available to home gardeners as Green Light Wipe Out Tough Weed Killer for Lawns) Tall fescue is somewhat sensitive to the product. 

*Home and garden product available

⁺Tall fescue somewhat sensitive to product

Timing of herbicide applications is critical to effect to effective control.  Ideally, the herbicide application should be made as soon as the nutsedge reaches the 3-8 leaf stage. None of these products will control fully mature plants.   It is likely that repeat treatments will be required in 6-8 weeks after the first.  Late summer applications are less effective because by then new tubers have formed.  As well, it may take multiple years to really get the nutsedge under control so persistence is important. 

Finally, to be enhance whatever product you use, add a non-ionic surfactant to the spray (if allowed by the label) which will help the herbicide penetrate the waxy cuticle of the nutsedge. 

For more information on nutsedge in other landscape areas, to UC IPM to view the current Pest Note:  http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7432.html

I guess I better get on that huh?