Which growth stage of target grasses is typically most susceptible to glyphosate in brush control?

• A. Dormant winter season
• B. Seed formation
• C. Active vegetative growth, typically during late spring to early summer when leaves are green and expanding
• D. Mature flowering stage

Answer: (C)

Glyphosate acts systemically by moving from the leaves through the plant to growing points. It’s most effective when the plant is actively photosynthesizing and producing new tissue, because these actively growing parts provide the best sites for uptake, translocation, and disruption of essential growth processes.

Dormant plants have little to no leaf area and minimal metabolic activity, so there’s little for the herbicide to absorb and move, making glyphosate far less effective. During seed formation, growth is redirected toward reproductive structures, and overall tissue expansion slows, reducing uptake and movement to meristematic areas. In mature flowering plants, vegetative growth is limited and the plant is allocating energy to seeds, again reducing the amount of new tissue that glyphosate can target.

Active vegetative growth, typically in late spring to early summer when leaves are green and expanding, provides abundant foliage for absorption and robust translocation to meristematic regions. This is when glyphosate can most effectively disrupt growth and achieve better brush control.