How Does Weed Killer Kill the Plant?

Written by russell huebsch
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How Does Weed Killer Kill the Plant?
A common weed. (Image by, courtesy of Neal Fowler)

Anyone who has a garden knows that weeds can ruin the aesthetic pleasure of a landscape. Weed killers sometimes mystify people because they destroy weeds and leave "good" vegetation alone. Even weed killers that target specific plants use a rather basic method for herbicide. Before using a weed killer, people should consider the environmental impact of herbicide chemicals.


For most of the history of man weeds were just a nuisance removed to make room for crops. Only a few passing references to weed killer appear before the 1900s, reports F. L. Timmons's history of weed control. The first widespread weed killer, acetic acid, also known as 2-4, D and short for 2,4-dichlorophenoxy, was developed during the early 1940s.


Acetic acid, still in use today in many weed killers, selectively destroy plants known as dicots. Most weeds fall into the category of dicot. A dicot is any plant that forms two tiny leaves upon germination, which act like an embryo for the plant. Monocots are impervious to acetic acid; most popular crops like rice, corn and wheat are monocotic, according to the Boston Globe.


Selective herbicides are not as popular as glyphosphate, which kills all types of plants, reports the Boston Globe. Non-selective herbicides---like glyphosphate---prevent plants from photosynthesising, the process plants use to absorb carbon dioxide and create their sustenance, reports Cindy McNatt of the OC Register. A third type of weed killer---total vegetation herbicide---prevents the weed from growing and future plant growth of any kind.


Weed killer effectively kills plants, but often has unintended consequences. Some herbicides are persistant enough to stay in soil for weeks and even months, preventing almost all plant growth. Weeds can leach herbicide that make their way into desired vegetation, reports Cindy McNatt. Rainfall can pick up weed killer and contaminate water sources all the way to the ocean.


Home and garden enthusiasts like Cindy McNatt recommend that horticulturalists try natural herbicidal remedies, or at least a more selective weed killer. A hoe is the simplest and still effective tool to get rid of weeds. Properly placed mulch can prevent weeds while improving the plants people usually wish to keep. Consider researching the type of weed infecting your garden and find an applicable weed killer.

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