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Understanding Herbicides
by Charlie Dobbin
by Charlie Dobbin

Charlie Dobbin, B.Sc. (Agr), is well known horticultural expert with professional gardening experience in a wide range of areas.

Her love of gardening and her easy manner is evident in her delivery of all her gardening seminars. She has a natural enthusiasm that makes her demonstrations both informative and fun.

Charlie was the Editor and Feature Writer of the White Rose Yard & Garden Guide. This company has now ceased to exist.

May 26, 2002

There always seems to be a few subjects in gardening where there is a communal misunderstanding. The biggest area by far is in the realm of chemicals. 

At fault lies the terminology in this area which is unusual, difficult, and unless you have a degree in chemistry, unfathomable. ‘Herbicides’ is one of those words. ‘Pesticides’ is easy. A pesticide is used to kill pests – garden pests that is. A herbicide on the other hand does not kill herbs. And to further complicate the issue, products like WipeOut and Roundup have entered the scene.

There are 2 basic types of plants - monocots (all the grasses) and dicots (all the other plants that are not grasses). When you use a herbicide you have to be specific about what you want to destroy. 

So, let’s start with some simple facts.

  • A herbicide kills weeds (dicots).
  • A herbicide will also kill your petunias, peonies, tomatoes, hydrangeas (dicots) etc. or anything else that is not a grass.
  • A herbicide or weed killer can be used on your lawn to kill weeds – do not use it in the garden.
  • Roundup and WipeOut kill everything – weeds and grasses.
  • Never use Roundup or WipeOut on your lawn. It will kill the grass. These products were designed to be used on patios, walkways, driveways or other areas where plant growth of any kind is not wanted.

If a mistake is made with one of these chemicals, which it very often is, severe damage can be reduced by watering the area thoroughly. If some herbicide is sprayed on your daisies or WipeOut gets on your lawn, wash the leaves of the plant and soak the soil thoroughly. You may not prevent all damage but it could mean the difference between losing the plant and saving it.

The biggest mistake a lot a people make is that they do not read the label and the instructions on the chemical before using it. This can lead to a lot of grief. Take 5 minutes to read the instructions. This is far less work than replacing an entire lawn or your perennial garden.


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