How to Kill St. Augustine Grass but Not Flowers

St. Augustine grass is a warm-season turf that invades flowerbeds in the late spring through early fall. Because this grass type survives in a variety of soils, gardeners may experience weed problems in their sandy or loamy yard areas. Often, gardeners see this grass spread from their own lawns or pop up within flowerbeds. Grassy weeds are removed through cultural or chemical methods. Choosing an herbicide that does not harm ornamental plants is imperative. Also, spraying herbicides at the right time in correct manner results in effective St. Augustine grass removal.

Post-emergent herbicide
Shovel
Trash bag
Mulch
Paintbrush
Broad-spectrum herbicide
Landscape fabric

Instructions

- 1
  Apply a post-emergent herbicide to St. Augustine grass on a dry, wind-free day. Use an herbicide that contains the active ingredient sethoxydim, which is formulated to kill grassy weeds and not broadleaf plants.
- 2
  Dig up the dead grass or work it into the soil with a tiller. Burn or throw away the dead foliage.
- 3
  Spread a 3- to 4-inch layer of mulch around your ornamental plants to keep St. Augustine grass from creeping back in from the yard. Keep the mulch 2 to 3 inches away from the base of your flowers. Mulching right next to flowers keeps their immediate areas from drying out and offers a hospitable environment for diseases.
- 4
  Dip a small paintbrush into an herbicide that contains glyphosate and apply to St. Augustine grass that pops up through the mulch or is growing next to flowers. Glyphosate kills off all types of vegetation, so avoid contacting surrounding plants.
- 5
  Pull out grass growing near ornamental plants. St. Augustine grass spreads through stolons or extensive underground roots. To pull out the entire root system, wet the area to soften the soil.

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