Weeds
by Dr. Robert Black, Consumer Horticultural Specialist
 
Weeds are common to all lawngrasses. They increase the maintenance cost of a lawn, reduce the land value and in some cases contribute to allergies and poisonings.

Weeds compete with all desirable plants for water, nutrients and sunlight. They also harbor insects and diseases that might attack lawngrasses, trees and shrubs.

Lawns which are properly maintained are less apt to be plagued with weeds. A vigorously growing lawn provides little area for weed seed to germinate and will usually smother out those that do germinate.
 
The use of chemicals to control weeds in parks, recreational and public areas is a relatively common practice. Herbicides (weed-killers) are rapidly being accepted and there are chemicals available to control broadleaf weeds and grasses in lawngrasses, around trees, ornamental plants, along ditches and fence lines, in areas difficult to maintain with mechanical equipment and in annual flowering plant beds.

Before you can effectively control weeds and grasses you must first be able to recognize your weed problem. Weeds can be classified into three broad categories. First, there are the annuals which complete their life cycle in less than one year and are usually easiest to control. There are summer annuals, such as crabgrass, goosegrass and Florida Pusley and winter annuals such as annual bluegrass, common chickweed and henbit.

The second category is the biennials, which require more than one year, but less than two years, to complete a life cycle. Cudweed and bull thistle are examples of this group.
 
The third and most difficult group to control are the perennials. They live for more than two years and may possibly last indefinitely.

Perennials are classified according to their method of reproduction. There are two types, the simple and the creeping perennials. Simple perennials reproduce by seed only and examples are dandelion, dock, broadleaf plantain and Florida betony. Creeping perennials reproduce by both seed and vegetative parts and are the most troublesome to control. Examples of this group are wild strawberry, Creeping Beggarweed, Dollarweed (Pennywort), bermudagrass, nutgrass and johnsongrass.
 
Herbicides can be useful if applied properly and incorporated into the overall weed control program. Both pre-emergence and post-emergence herbicides, in combination with mechanical equipment, are needed for a good weed control program. Ask your local county agent about the proper chemicals to use on specific weeds.

Calibration of equipment is an important part of any herbicide application. This is simply making the necessary adjustments to the sprayer so that the proper amount of chemical will be applied to a specific area.

Regardless of the herbicide used, care should be exercised and the chemical must be applied in accordance with instructions on the manufacturer's label. Also be sure that the herbicide you buy states on the label that it can be used on your particular lawngrass. Using the incorrect herbicide on your lawn can seriously damage it.