Does Glyphosate Have Pre-emergent Properties?

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My wildlife biologist insists that Glyphosate (“Roundup”) can be applied immediately prior to planting any seeds because, he contends, that Glyphosate has no pre-emergent properties — that it kills green plants by absorption via the growing leaves.

On the other hand, two different county extension experts tell me that “the label” for Glyphosate states that it does indeed have pre-emergent properties for 7 days and thus any plants that germinate within those 7 days will be negatively affected by this herbicide. I assume that Roundup Ready seeds would be immune.

What is your opinion/fact on this? Can I spray Glyphosate one day and safely plant seeds the next day? A major reason for my question is that my wildlife biologist has a sprayer and drill he will let me use, but wants them returned ASAP. Also, in spring, there will likely be limited opportunities for prime planting — not too dry, not too wet, rain in the forecast, etc. It would sure be easier if I could spray then plant during one good (weather) opening.



Glyphosate’s mode of action is absorption through living plant tissue. It has no pre-emergent properties for any plant I’ve ever researched. In fact, I just checked the Glyphosate label for wheat, corn, and soybeans (cereal and grain crops). It says

Preplant, Preemergence, At-Planting

USE INSTRUCTIONS: This product may be applied before, during or after planting of cereal crops. Applications must be made prior to emergence of the crop.”

I have sprayed and planted in one day, and never experienced a problem with the crops I’ve planted.

Like you, I have limited days to plant when the conditions are favorable. I’d suggest also checking out the herbicide Gramoxone. It kills extremely rapidly (in a day for most annual weeds). However, it only top kills. Some perennial plants will resprout. This may be a good option if you have to spray one day and plant the next. Gramoxone requires a pesticide applicators license.

Growing Deer together,