Sedges look a lot like grasses at first but are not the same. They can be very difficult to control. As one article said they are like the good witch and the bad witch from the Wizard of OZ. Some are used for ornamental purposes and others are invasive and difficult to eradicate once they are established.
To make matters worse, there are different types of the invasive ones and they require different strategies. Some of the common problem ones are yellow nut sedge, purple nut sedge, umbrella sedge, globe sedge, cylindrical sedge and annual sedge.
Prefer Moist Environments
Sedges tend to like moist environments, sometimes marshy, although some varieties do fine in drier soil. They tend to grow taller, have larger blades to their leave and have seed heads that are much larger and not as fine and delicate as grass seed heads when you let grass get that long. Most of the sedges also have a triangular stem although some have round stems.
Since most sedges like moisture, one way to control them is to add soil to low lying areas so water doesn’t collect there as much. Another way is to keep the grass mowed so the sedge can’t form seed heads. If they are in the garden where you don’t mow, even if you don’t pull them, make sure that you cut off the seed head before they drop their seeds.
Different Strokes for Different Folks (Or Sedges)
You also need to identify which sedge or sedges you have so you can plan the correct means of attack. Some sedges are perennial and others are annual. If yours are annual, the key to control is to prevent it from dropping any seeds.
If you have a perennial variety, you have more of a problem. There are some herbicides that could be effective. They are different from ones for grasses and broadleaf weeds. One is called SedgeHammer.
On the Scott’s website it says that the nutsedges are perennial. They have roots that can extend down 10-14 inches and they have small tubers or nutlets that grown on the roots that new plants grow from. So if you don’t get all of the root, they just grow back.
Long Grass or Short?
Scotts says to mow the grass long. It says that nutsedge are stimulated by short cutting and by leaving the grass longer it helps the grass to crowd out the nutsedge.
An article by two weed scientists from the University of Tennessee say to cut the grass quite short and cut it a couple of times a week to control nutsedge. Not sure whether to believe them or Scotts.