How can I control the crabgrass in my flower bed?

May 4, 2006

Question How can I control the crabgrass in my flower bed?

Answer There are two grasses that give folks a fit in their flower beds. One is crabgrass. This annual grass is considered a weed whether it’s growing in your lawn or flower bed. Since it is an annual, this plant can easily be controlled with preemergence herbicides. However, once you see the grass growing, it is way too late for preemergent control.

The other aggravating grass is bermudagrass. This perennial plant lives a dual life. When bermudagrass is growing in a manicured lawn, putting green or ball field, then it is highly prized. However, when it crawls into a garden, then the name of this grass actually changes from bermudagrass to either wire grass or joint grass. Neither of these names is used in an endearing manner.

Grassy weeds can be removed by hand. In the old days, a tool called a hoe was often used to “chop” (separate the roots from the leaves) weeds. Nowadays, a hoe is almost as foreign to gardeners as a mule is to a farmer.

Annual and perennial grasses can be eliminated in most landscapes using postemergence herbicides that control only grasses. These chemicals are referred to as graminicides. Gramineae (also called Poaceae) is the name of the grass family where the weedy and turf grasses belong. There are four graminicides labeled for use in horticultural crops: fenoxaprop, fluazifop-p, sethoxydim and clethodim.

Fenoxaprop (Acclaim) is labeled for postemergence control of summer annual grasses in landscape beds. It is most commonly used to control crabgrass in fescue. Clethodim (Envoy, Select) is generally considered to be one of the better graminicides on perennial grasses including bermudagrass.

Fluazifop-p (Fusilade II, Ornamec, Grass-B-Gon) also controls perennial grasses including bermudagrass and johnsongrass. Sethoxydim (Vantage, Take-Away, Poast) controls both annual and perennial grasses. Poast / Vantage may control crabgrass better than Fusilade II or Envoy / Select, but is generally considered to be weaker on perennial grasses like bermudagrass.

In general, graminicides are more effective when applied to young, actively growing weeds, and less effective when applied to large, mature weeds. Avoid treating over the top of flowering plants. If you must spray over a flowering bed, do not spray in the heat of the day. Treatments on cool cloudy days cause significantly less injury to the flowers.

If you have any questions about weed management, then visit this website http://www.ces.ncsu.edu/depts/hort/consumer/hortinternet/weeds.html If you don’t have internet access, then call the Cooperative Extension Office at 893-7533, write us at PO Box 1089, Lillington, NC 27546, or email me at gary_pierce@ncsu.edu Isn’t it funny how the terms hoe, grass and mule have totally different meanings today than they had 25 years ago?