Weeds and grass in flower beds compete for water and sun, limiting healthy growth of bedding plants. To control weeds and grass in flower beds, apply weed and grass killer that doesn't injure bedding plants. Pre-emergent herbicides are used before the weeds break through the soil, while post-emergent herbicides can be used if weeds are already growing.
Weeds and grass that invade flower beds are either annual or perennial types. Annual varieties include crabgrass, carpetweed and spurge; they live for one season before producing seeds and dying off. Perennial weeds and grass, including dandelions, Bermuda grass and dollar weed will return every growing season unless they are controlled. Instructions and details on the herbicide container should be reviewed before using the herbicide to avoid damaging or killing plants.
Glyphosate, a non-selective weed and grass killer, can be used before planting to control weeds in flower beds. After bedding plants are planted, spread mulch on the flower beds to discourage weed growth. Weeds should be removed as soon as they are spotted or before seeding. Annual weeds that appear after bedding are in the ground can be removed by hand, but this can be time-consuming. Using a pre-emergent herbicide prevents annual weeds from appearing in the soil, eliminating the need for hand weeding.
Trifluralin, a commonly used pre-emergent herbicide, is a major ingredient in Greenview Preen or Miracle Grow garden weed preventer. Roundup-Pro is a systemic herbicide that kills weeds and grass as it moves through their systems; it is commonly used for perennial weeds. Contact post-emergent herbicides, such as Spectrum systemic grass and weed killer, kill only the portion of the weed or grass that has been sprayed and is considered an effective controller of annual weeds. Contact post-emergent herbicides kill weeds without damaging plants.
Read the label for all safety requirements and wear gloves or other protective clothing while using the product. Some herbicides may require more than one application before weeds are killed. If non-selective herbicides are used as a spot treatment, avoid accidental spraying of bedding plants. Another available weed killer, 2-4D, can be used as a spot treatment in flower beds to kill broadleaf plants. Use caution when spraying 2-4D around broadleaf bedding plants such as tomatoes and roses.
Some weeds can be removed or controlled without herbicides. Incorporating plastic liners and mulch into flower beds can prevent unwanted weeds and grass from appearing. A ground cover or a plant with a heavy matting can also choke out weeds in flower beds. Annual weeds can be pulled out by hand or through solarization, a process of covering flower beds with clear plastic for up to 8 weeks. During this period, heat from the sun kills the weeds under the plastic.