Herbicide Tips

Here are a few tips on the two most commonly-used herbicides by homeowners. Before reading them, please read the Herbicide Considerations page and watch the video to learn a little about safety and legal concerns.


The tips below are not intended to be comprehensive. For more details, you should read the label and other documents to find the best treatment for the species you are treating.


Which herbicide should I use?

Here we only talk about glyphosate, a non-selective herbicide that kills all types of plants, and triclopyr, which kills broad-leaf plants but not grasses. There are also herbicides available that only kill grasses, but most of them are not aquatic-safe. Aquatic-safe is best, because amphibians live far from water bodies, and in any event, water runs downhill.


Glyphosate is enough for most species, but triclopyr may be used instead or in addition for some tougher plants. Note that there are several different types of triclopyr. Be sure to get the right one! This video explains the differences. For basal bark treatment, you would need Triclopyr ester mixed with an oil such as JBL oil. For other applications, you would use a Triclopyr amine or salt. Professionals use Garlon 3a, which is a concentrated triclopyr salt.


Herbicides come either pre-diluted for foliar sprays or as concentrates. For cut-stump or hack-and-squirt methods, you need the concentrates, which usually come in huge containers for professionals. Here are some products that come in small quantities.. 


For foliar spray, you can get the concentrate and dilute it yourself, which gives you control of the surfactant choice and the degree of dilution, or you can buy pre-mixed versions such as RoundUp. However, it is difficult (and perhaps impossible) to find pre-mixed, diluted glyphosate that is aquatic safe.


What else do I need to buy? (These product links are just examples, not endorsements)


Bring along a bottle of water (carefully labeled so no one ever drinks from it and in a bag to keep it clean) for additional wash for eyes or skin.


How do I mix herbicides?

Getting herbicide out of a bigger bottle into a smaller one without spilling is not easy. A couple tricks:

  • Use a spill tray (such as a large paint tray) as a base when pouring and mixing. 

  • If you have a gravel driveway, do it there.

  • When opening the bottles, don’t peel off the paper/foil seal. Instead, make a smaller hole in it (and maybe a second small hole to vent).

  • Pour into a measuring cup first. 

  • Write the contents on the receiving container. Cover the label with clear tape to prevent smudging or staining.


Do

  • Mix outdoors.

  • Agitate your mix before using in case of settling.

  • Keep your PPE separate from the herbicides. Once the seal is broken, there will be vaporization even when the lid is closed.

  • Wash your hands before eating, chewing gum, smoking, or using the bathroom.

  • Wash your clothes and yourself as soon as you get home.

  • Buy only enough product for that year. Dispose of excess at the hazardous waste collection.

  • Write ‘poison/herbicide’ on all components you plan to reuse

  • Keep all components in a dedicated (and similarly labeled!) container, such as a 5 gallon bucket with a lid. If your herbicide bottle is too large for that, store it in a bin in case it springs a leak.


Don’t

  • Use anything that could be mistaken for a food container or utensil.

  • Store herbicides indoors. If you need to transport them in a car, keep the windows open. 


Dilutions

Some of the labels have recommended dilutions, but note that many invasive species are not mentioned on the labels.

Some helpful resources:


Important note: when the instructions tell you the percentage needed, they are talking about the percentage of concentrate, not percentage of herbicide. Here is an example.

Let’s say you are making 100 ounces of your mixture, and the instructions are for 1%. You would use 1 ounce of the herbicide concentrate and a total of 99 ounces of water, surfactant, or marker dye. It doesn’t matter if the label says 53.4% glyphosate or 8.8% triclopyr - it is still 1 ounce of herbicide concentrate to make 100 ounces of the mixture. The herbicides are all standardized this way.


When do I do the treatments?

Don't use herbicides if rain is expected within 2 or better yet 12 hours. 

Don’t use herbicides when the temperature is over 85 (or better yet, over 80)

Otherwise the timing depends on the species. It is critical to look that up first.


In general, it is ideal to kill plants before they start to go to seed.


For most species:

Cut-stump or hack-and-squirt

  • Can be done any time of year except when the sap is rising (March through May, though it might start to work in early May.)

Foliar 

  • After the plants have fully leafed out (so the plant is no longer pushing nutrients and water out to the leaves faster than it is carrying them back to the roots) and before the first frost. For plants such as vines that keep growing all season, some time in May is not unreasonable, but it is likely to be less effective than waiting until July.

  • For evergreens such as English Ivy, Vinca, or Wintercreeper, it will still work in the winter if it is above freezing. That is a good time because other plants are dormant. A popular mixture is 2% glyphosate with 2% triclopyr with a surfactant.

  • Because you never spray higher than your waist (or hips or knees, depending on who you ask), the usual technique for larger plants is to cut them back first and wait for the regrowth, catching it before it gets too large again.

Notable exceptions include Tree-of-Heaven and Japanese Knotweed. But always look it up!


How do I apply it?


Cut-stump

This method only works on “woody” plants: trees, shrubs, and woody vines. Dab the cut stump immediately, covering the entire stump for smaller stems or a ring around the edge for large ones (you only need to treat the cambium). It needs to be immediate, because the little tubules seal up quickly after cutting.


Foliar

Be sure to cover at least 90% of the leaves and include the terminal leaves. Spray to your side, or walk backwards.


Wicking

A cloth glove worn over your chemical-proof glove can be used to target one plant at a time. You spray your gloved palm with herbicide and stroke upward along the leaves of the plant. Here is a video demonstration.


These are only some of the methods. Check out Blue Ridge PRISM for more.