Weed Control in Flower Beds

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Kelly Jackson
Christian County Extension Office

Weed Control in Flower Beds

Grass and broadleaf weeds in flowerbeds are a ‘thorn in the side’ to most avid gardeners. As temperatures become favorable for annuals and perennials to be planted in beds, the soil is also right for weed seeds to germinate.  Take heart, you do have some options.  If you are just beginning a flowerbed, then you are in the prime position to eliminate your weed woes before they ever begin.  After you select your new bed site, mark the area with a garden hose or rope.  Spray a non-selective herbicide, such as Roundup, to the area and wait for the results to appear.  As weeds and grass die in your future planting site, more sunlight will reach the soil and encourage new weed seeds to germinate.  After your new crop of weeds have emerged, make a second herbicide application.  Pay close attention to areas where bermudagrass is invasive as it can be a stubborn plant to eliminate.  If the soil in the area is to be tilled, plan to spray an additional time.  After tilling, level the soil to its final form and wait for any new weed seeds brought up by the tilling process to germinate and then treat. Preparing the planting site is the step most gardeners rush, however eliminating weeds is the most important process in preparing a bed and doing it right may take you four to six weeks to complete. Landscape fabric is a key method of weed control in beds that will be in place for several years and works best around woody trees and shrubs. Never substitute landscape fabric for plastic. Plastic will decrease water and air movement to plants root zone. A mulch layer 2-3” deep is also very important in a weed control plan.  Mulch will help minimize germination and emergence of annual weeds. A physical barrier, such as landscape edging may help keep lawngrass from spreading into beds. Combining these methods during the planning and preparing of flowerbeds can help keep your beds weed-free.

But what about your beds you prepared before you had this information?  There is still hope. Some of the controls mentioned above can be applied to your existing beds.  For example, where weed problems are minimal, hand pulling weeds and applying a fresh layer of mulch can be very effective.  But if your weeds have taken control you may want to take more drastic measures.  Pre-emergence herbicides work in beds to prevent new weeds from becoming established.  They will not work on weeds already established in beds. Examples include Preen, Spectracide Weed Stop and Miracle-Gro Garden Weed Preventer. Be sure to read their labels closely since some pre-emergence herbicides may require irrigation to become active and some are not suggested for use in annual beds. Post-emergence herbicides control weeds after they have already emerged. Non-selective herbicides, like Round-up or Finale, can be used in beds as a directed spray against both broadleaf weeds and grass weeds.  Damage to your ornamentals can occur if spray contacts the plant. Non-selective products are best used in beds with woody trees, shrubs or groundcovers. Bermudagrass or dallisgrass can be controlled using herbicides selective toward grass weeds such as Fusilade II or Vantage. These products are safe to use in any bed that does not contain ornamental grasses. Yellow or purple nutsedge problems can be controlled with a product called Manage, but this product is not recommended for use around annuals and perennials.

Although these products may not completely eliminate your weed problems, they can help, especially in hopeless situations.  Remember to always read and follow the label for any herbicide or pesticide.