Herbicides are not a recent invention; there have been various types of organic herbicides available for centuries. Within the latter half of the 20th century, multiple chemical combinations have been added to the list creating a herbicide for nearly any type of weed or vegetation problem. This has created several subcategories under three main categories. Understanding these categories and their applications will help create the beneficial result desired in property maintenance and management.
What is Classified as a Herbicide?
Chemical compounds used to kill or control plant growth are labeled as herbicides. The delivery method varies, along with the results, depending on the composition of the chemicals. Herbicides use one of two delivery methods, direct contact or systemic absorption to delivers the chemicals to the plant. The first method is used on vegetation above ground, while the second is used to attack roots and cells. Additionally, there are two types of herbicides, selective and non-selective.
What is a Selective Herbicide?
Look for selective herbicides to attack specific attributes of the targeted plant only. Use selective herbicides when you do not want surrounding vegetation affected; this is usually the case in weed applications for lawns and turfgrass or flowerbeds. Application of selective herbicides is conducted after the weeds have grown into plants above ground; this type of herbicide cannot be used against seeds to prevent germination. Because of this factor, multiple applications throughout the season are often needed; both climate conditions and the life cycle of specific weeds will help determine the number of applications during the growing season.
What is a Non-selective Herbicide?
Use non-selective herbicides when elimination of all vegetation in a given area is warranted. Caution must be used when applying this type of herbicide so as not to accidentally kill off other vegetation that is wanted in the area. Examples of this use would be the elimination of poison ivy patches, crabgrass and vegetation growing within cracks of hard surface areas such as driveways or walkways.
Look for two types of herbicides within this category; pre-emergent and post-emergent herbicides. Consider using pre-emergent herbicides when you want to stop seed germination; apply post-emergent herbicides to grown plants. Find an example of pre-emergent herbicide in brands such as Preen, where the granual herbicide is worked into the soil.
Use a post-emergent herbicide such as liquid Roundup to kill already-growing vegetation in the same manner as selective herbicides are used. Think about the overall result wanted when choosing a non-selective post-emergent herbicide; some types destroy vegetation, but still allow the soil to function as a growing medium, while other herbicides of this category destroy both the vegetation and make the soil unusable to any vegetation for a period of time.
What are Organic Herbicides?
Organic herbicides are naturally produced substances used to control unwanted vegetation. Examples include boiling hot water, vinegar and acetic acid. Use organic herbicides on younger weeds and for spot control. While some organic herbicides are not as effective as synthetic herbicides, others such as boiling water can be; pouring boiling water on vegetation can burn and kill foliage and roots quickly but must be applied to individual plants.
The Sustainable Agriculture Laboratory division of the U.S. Department of Agriculture conducted a study on the use of vinegar as an organic herbicide. This study found that vinegar has an 80 percent or higher rate of effectiveness on select weeds when used as a spray concentrate with a 10 to 20 percent concentration. Consider the pH level of the soil when using this method as multiple applications can alter the acid content of the affected soil.
What Health Concerns are Associated With Herbicides?
Read the label when using any type of herbicide. Research any material available on the specific herbicidal remedy you intend to use; this will provide information about how and when to use the herbicide, but also what precautions must be taken to make the use safe and effective.
Research conducted at the French University of Caen, published in "Chemical Research in Toxicology" in 2008, found that herbicides such as Roundup contain chemical agents which can "cause cell damage and even death around residual levels to be expected, especially in food and feed derived from R formulation-treated crops."