How to Use Herbicides

While handpicking can be an effective tactic against weeds, sometimes a gardener needs a stronger weapon in her arsenal. When used correctly, herbicides can be an effective tool that allows gardeners to spend less time battling weeds and more time tending to wanted plants.

All herbicides must be used according to the directions on the label; failing to follow the label is not only dangerous to yourself, your garden and the environment, but it is against the law.

Widely used by gardeners, glyphosate is a nonselective herbicide that injures or kills all weeds and can also kill desirable plants. The amount of herbicide to apply varies depending on the type of plant you wish to control; follow rates on label.

Put on a long-sleeved shirt, long pants and socks with shoes. You may also want to wear chemical-resistant gloves, such as rubber gloves, and protective eyewear such as goggles or safety glasses.

Fill the tank with clean water, mixing in the herbicide afterward. Unless the label states otherwise, mix in a surfactant to help the herbicide stick to the plant.

Spray solution directly onto the foliage of the plant you wish to control, covering the entire top half of the plant and at least half of all leaves. Spray until leaves are wet but not until chemicals run off the plant. Agitate the sprayer back and forth occasionally to keep the contents mixed.

Windy conditions cause herbicides to drift, potentially causing them to damage or kill nearby desirable plants.  Drift potential is lowest when wind speeds are between 2 and 10 miles per hour.  Early mornings and evenings tend to be less windy. 

Do not apply herbicides if rain is expected. If heavy rainfall occurs after spraying, you may need to spray again. 

Triclopyr is a selective herbicide that controls woody plants and annual and perennial broadleaf weeds. It is often used to control weeds in lawns. Conifers are sensitive to triclopyr; employ extra caution to avoid drift in areas with conifers.

Amount of herbicide to apply varies depending on the type of plant you wish to control; follow rates on label.

Put on a shirt with long sleeves, long plants, shoes with socks and chemical-resistant gloves.

Fill tank 1/2 full with clean water. Agitate the tank back and forth and add herbicide. Continue to agitate at a moderate speed as you add the remaining water. Without continuous movement, the water and herbicide will separate. Add surfactant if recommended by label.

To control woody plants, spray thoroughly to wet leaves, stems and root collars. 

To control broadleaf weeds in turf, spray weed foliage while weeds are actively growing, from early spring until fall.

To avoid injury to lawns:

Do not water for 24 hours after applying triclopyr.

Do not apply to lawns that are stressed from heat or drought. 

If re-application is necessary, wait four weeks to avoid injury.

Pendimethalin is a pre-emergent herbicide that controls certain broadleaf weeds before they emerge from the soil. It is often used to control weeds in lawns and landscapes. The amount of herbicide to apply varies depending on the type of plant you wish to control; follow rates on label.

Put on a shirt with long sleeves, long plants, shoes with socks and chemical-resistant gloves.

Fill tank 1/2 to 3/4 full with clean water. Agitate the tank back and forth as you add herbicide. Fill the remainder of the tank with clean water, continuing to move the tank.

Apply evenly to turf or other area in the garden where weeds are expected to emerge, agitating the tank back and forth as you spray to keep the solution mixed. Apply in spring, before weeds germinate.

For stubborn weed infestations, you may need an additional application. Apply again in five to eight weeks, or as directed by label.

Store herbicides in a secure location away from children, pets and food products. Store glyphosate at a temperature above 10 degrees Fahrenheit and triclopyr at a temperature above 28 degrees Fahrenheit.