What precaution should you take regarding herbicides with broadleaf activity under trees or shrubs?

What precaution should you take regarding herbicides with broadleaf activity under trees or shrubs?

• A. They are always safe under trees.
• B. Use them only if you are certain they will not leach.
• C. They will never leach.
• D. Apply them at full rate.

Answer: (B)

Under trees and shrubs, how a herbicide moves in the soil is crucial. Broadleaf herbicides can be carried downward by water in the soil and reach the root zones of nearby trees and shrubs. Since the roots under a tree extend well beyond the canopy, there’s a real risk that the chemical will move into the root zone and injure desirable woody plants. Because leaching depends on soil type, drainage, rainfall, and irrigation, you should only apply these herbicides if you are certain they will not move into and affect non-target roots. In practice, that often means avoiding applications under trees unless the label confirms it’s safe and you can ensure conditions won’t allow leaching. The other ideas—claiming they’re always safe, that they will never leach, or applying at full rate—do not reflect how movement in soil and root uptake can occur.

Under trees and shrubs, how a herbicide moves in the soil is crucial. Broadleaf herbicides can be carried downward by water in the soil and reach the root zones of nearby trees and shrubs. Since the roots under a tree extend well beyond the canopy, there’s a real risk that the chemical will move into the root zone and injure desirable woody plants. Because leaching depends on soil type, drainage, rainfall, and irrigation, you should only apply these herbicides if you are certain they will not move into and affect non-target roots. In practice, that often means avoiding applications under trees unless the label confirms it’s safe and you can ensure conditions won’t allow leaching. The other ideas—claiming they’re always safe, that they will never leach, or applying at full rate—do not reflect how movement in soil and root uptake can occur.