Selective Herbicides

• Selective herbicides formulated to kill grassy weeds are the only post-emergent herbicides that should be used in flowerbeds, according to North Carolina State University. Because broadleaf-killing herbicides can kill off your ornamental plants, avoid using them in your garden. You can apply selective grass-killing herbicides over your garden to eliminate existing weeds, but check the label first to ensure the chemicals won't kill flowering plants. Apply the herbicide on dry days to allow the chemicals to absorb through the foliage.
  
  

Broad Spectrum Herbicide

• While broad spectrum herbicides can be used on broadleaf weeds, they cannot be sprayed on ornamental plants. Use a broadleaf herbicide that contains glyphosate because it leaves little soil residue. Glyphosate works by inhibiting the protein production in weeds. Paint the herbicide on the leaves of broadleaf weed, using a small paintbrush. You can also cover a nearby plant with a piece of plastic and spray the foliage of the weed. You may need to reapply the herbicide in a few days to eliminate the weed.
  
  

Landscape Fabric

• Landscape fabric prevents grassy and broadleaf weeds from invading your garden and smothers existing weeds. The landscaping fabric works by smothering the weeds and their seeds. Cut a piece of landscape fabric to the size of your flowerbed. Create X-shaped cuts in the fabric for flowers to poke through. Secure the fabric over the garden with landscape pins. Because landscape fabric can deteriorate in the sun, spread a 2- to 3-inch layer of mulch over it.
  
  

Mulch

• Mulch not only prevents grassy and broadleaf weeds from encroaching on flowerbeds, it also helps with keeping soil moist. In addition, organic mulch such as compost, pine needles, oak leaves, pine cones and grass clippings add nutrients to the soil as it decomposes. If you decide to use grass clippings as mulch, use clippings that have not been treated with any chemicals. Spread a 2- to 4-inch layer of mulch around your flowers and along the perimeters of the garden bed.