One of the aggressive weeds in lawns, flower beds and gardens is nutsedge, aka nutgrass. Nutsedge has a distinctive three-angled stem that is tough and fibrous. It can persist in an environment for years until the conditions are right for growth. Nutsedge spreads by seed, tubers, cultivation and can be introduced in topsoil, compost and nursery stock. One of the drawbacks to over watering or poor drainage is the sudden appearance of nutsedge. Why? Because this stuff likes it moist. So, if you have nutsedge show up take a look at the irrigation system, including possible leaks in that area.
Controlling nutsedge is a process not an event. Post emergent herbicides are the most common and for me have been the most effective. One of the best is Sedgehammer. One package will cover 1,000 square feet and may require two to three applications. The other is called Sedge Ender. This Bonide product come in a hose end bottle and will cover up to 5,800 square feet. Neither of these products are safe for a veggie garden so read and follow the directions.
Now we go to the garden. I have tried some of the natural controls for nutsedge but all I did was hurt its feelings and not kill it. The most noninvasive way is to dig it out. The bad news is the nut may be 18” deep and you have to remove the nut to be successful. The other way takes a little time. Plan on not planting a fall crop. In August or September remove all the plants from the garden. Spread about ten pounds of molasses for every 100 square feet of dirt and work it in just a little. Next, cover the entire garden with two sheets of newspaper (the black & white sheets). Then spread the mulch (cedar mulch or hardwood mulch) of your choice over the newspaper an inch or so thick. In late February start working your garden as normal. What we have just done is to compost the entire garden. We (my dad and I) killed about 90% of the nutsedge on the first garden we tried this process on.