How to Identify Garden Weeds & Grasses

Updated November 21, 2016

Garden weed and grass identification is essential for choosing the correct herbicide. Certain weed killers, such as selective post-emergent herbicides, contain dicamba to kill broadleaved weeds, yet leave turf and grass weeds unaffected. On the other hand, post-emergent herbicides that contain fluazifop kill grassy weeds in broadleaved flowerbeds. In addition, annual weeds that show up in the spring and fall are controlled with a pre-emergent herbicide that prevents weed seed germination. Knowing which weeds pop up annually in your yard will help you determine which type of pre-emergent herbicide is needed.

Press a screwdriver into the first 6 inches of topsoil. Place a soil thermometer inside the hole to measure the soil temperature. Broadleaved weeds such as dandelions germinate and grow when soil temperatures are at least 10 degrees Celsius. Grassy weeds such as crabgrass sprout when soil temperatures are 15.6 degrees Celsius. If the soil temperatures favour a specific weed, you can narrow down the list of possible weeds you are dealing with in the yard.

Dig a 6-inch hole in the yard. Collect 1/2 cup of soil from the bottom of the hole. Conduct a soil pH test, using a kit. Weeds such as clovers grow at a soil pH of 6.4. Finding out your existing soil pH aids in weed identification.

Examine the tips of the weed. Grassy weeds have triangular tips, and sedges grow rounded tips. Broadleaved weeds are typically more colourful than grass or sedges.

Walk across the lawn, looking for weeds that are disrupting the uniform texture of the lawn. Dig up the weeds in question and place them in plastic bags. Take the weeds to a local nursery to obtain a positive identification.

Grab a handful of dirt next to a weed. Squeeze the dirt in your hand. Dirt that is crumbly suggests that your soil is sandy. Soil that releases water indicates the soil is clay. If the soil is malleable in your hand, it is loam. Weeds prefer to grow in certain soil types. Discovering the make-up of your soil can help you to identify the weed growing in the yard.


Identify weeds before they have a chance to mature. Young weeds are easier to kill with post-emergent herbicide than mature weeds.


Avoid composting any weeds dug up from the yard to prevent scattering their seeds.

Things You'll Need

  • Screwdriver
  • Soil thermometer
  • Shovel
  • Soil test kit
  • Plastic bags
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