When grassy weeds invade garden beds, it is important for gardeners to act fast before their ornamental plants become damaged. Weeds reduce the amount of sunlight, moisture, air flow and nutrients getting to your ornamental plants. Grabbing any type of herbicide may result in killing your landscape plants. Gardeners must use grass killers that are chemically formulated to remove grass and not their broadleaf plants.
Pre-emergent herbicide prevents grassy weed seeds from germinating. Gardeners use this herbicide type at the beginning of the growing season or right before soil temperatures favor grassy weed growth. For example, crabgrass seeds germinate when soil temperatures reach 60 degrees Fahrenheit, according to the University of Rhode Island. Apply a pre-emergent spray that contains trifluralin to control annual weeds within flower beds, as suggested by the University of California. Water the flower bed after applying the spray.
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Post-Emergent Selective Herbicide
Post-emergent selective herbicides kill existing grass without harming broadleaf plants. The best time to spray grassy weeds with a grass killer that contains fluazifop is when they are actively growing, according to the University of California. Other considerations must be factored for this type of weed killer to work. Spray your grassy weeds when you have a 48 hour window of dry weather. Spraying post-emergent herbicide before a rain prevents chemicals from absorbing sufficiently into the foliage.
Broad-spectrum herbicides will harm plants when used incorrectly. However, when broad spectrum grass killers are used properly they are effective against perennial grassy weeds. To use a broad spectrum herbicides, dip a small paintbrush into a the herbicide and apply in the foliage of the grass. You can also cover your plants with a piece of plastic and spray your grassy weeds. Herbicides that contain glyphosate will leave little soil residue, so you do not have to worry about replanting former grassy weed areas.
Gardeners can use a wide range of chemical-free grass killers. Landscape fabric is a type of mulch that prevents grass weed seeds and grass from encroaching on landscape plants. Gardeners install landscape fabric by making slits for the plants and laying the material over the flower beds. Other cultural ways of killing grass include hand pulling and digging. If digging up a grassy weed, try to remove as much of the root system as possible to prevent the weed from growing back.