Herbicide is the correct name for a Weedkiller, but “kill” is not always good word to associate with!
So a herbicide kills weeds, perhaps we need to establish some rules…
What is a weed?
A plant in the wrong place. What harm do they do? They limit the effectiveness of other preferred vegetation, making them susceptible to disease, or at least unhealthy growth pattern.
They are often controlled by manual means but sometimes the handweeding is not sufficient to keep weeds under control so we use a chemical herbicide, a variety grouped by activity or type of vegetation controlled.
Herbicides can be total (killing everything) or selective (to promote grass growth, for instance, by killing rival weeds in the same space). Either entirely spraying an area or spot treating just the visible growth, weed control is vital in the maintenance of most open spaces.
- Contact herbicides destroy only the plant tissue in contact with the chemical. Generally, these are the fastest acting herbicides, some results are noticed within hours. They are less effective on perennial plants, which are able to regrow from the unaffected roots. They kill all the green of the plant but not the future growth!
- Systemic herbicides are passed through the plant, either from foliar application through leaves down to the roots, or from soil application cutting supply of nutrients to the leaves. They are capable of controlling perennial plants and may be slower acting but ultimately more effective than contact herbicides. This process can take up to 4 weeks or longer in heavily infested areas.
- Soil contact systemic herbicides can be used to prevent future growth of weeds on “land not intended for vegetation”, such as fencelines or mulched pathways usually used only once per year and therefore more expensive. They form a layer on the soil surface which weeds cannot penetrate, reducing the need for further spot treatment.