Photo by Melody

Friend or Foe? Weed Identification

By Toni Leland (tonilelandFebruary 16, 2009

Do you know how to tell the differences between annual and perennial weeds? How they grow or spread? When seedlings first emerge, they all look alike!

Gardening pictureIn a few months, the soil will warm and all manner of seedlings will appear. Here are some tips for identifying them, through a variety of methods. Once you know what's growing in your garden, you can decide the best method for control.

What is it?
These weeds are common in a wide range of states, and are easily recognized. Of this list, five are common to all states; they are marked with an asterisk.
Identification of less familiar weeds will require research, or consultation with professional nursery staff or your local Extension agent. Often, weed seeds from another region will migrate into an area and adapt to growing conditions there. So, if the weed in the upper Midwest looks like something that is native to the Southeast, it is conceivable that seeds piggybacked on some other commodity from that area.

Sources of imported weeds
  • Mulch
  • Transplants from other gardeners or nurseries
  • Bird Feeders
  • Rodents: squirrels, chipmunks, mice

Weed Look-alikes

Many weeds have cultivated cousins, further complicating identification. Note the close similarities between the photographs below.


 Canadian Thistle Seedlings


Oriental Poppy early growth


Mugwort / wild chrysanthemum


Hardy Chrysanthemum


Field Bindweed


Morning Glory

So how do you go about identifying that strange plant growing amongst your precious perennials?

  1. Online sources often have photograph of seedlings. These are especially helpful because they have an interactive search function.
  2. County extension offices and/or state agricultural offices often publish weed identification brochures.
  3. The Weed Finder brochure from Ortho is available free from most places selling their products.
  4. University of Minnesota Extension publishes "Annual Broadleaf Weed Seedling Identification" (Extension Publication 89, North Central Region).
  5. Cooperative Extension Service University of Georgia publishes "Common Weed Seedlings", which includes color photographs of weed seedlings, as well as details.
  6. Many libraries have excellent references and publications relevant to your area.
  7. The USDA website has a wealth of information.

The biggest question for any gardener is: How Do I Get Rid of It?!

Understanding how the weed reproduces or spreads is important in identifying how to control it. Perennial weeds are particularly hard to control. The afore-mentioned weed ID resources will include this type of information, but here are some things to note:
  • Simple root systems succumb easily to foliar herbicides.
  • Taproots can break, and new plant will grow from piece left behind.
  • Plants that spread by stolons can intermingle with desirable plants, making use of systemic herbicide dangerous.
  • Pre-emergent herbicides can eliminate the problem for the following year.

Vigilance is required to stay ahead of the weeds, especially during quality growing weather. When those first green sprouts appear in the wrong place, do your homework. Summer is for other activities than weed-pulling!

I have found the following sites helpful.

University of California Statewide Integrated Pest Management Online

Horticulture & Home Pest News Online, Iowa State University Department of Horticulture

Bayer Advanced

Weed Identifier Online. Illinois Council on Food and Agriculture Research

Ohio Perennial & Biennial Weed Guide Online. Ohio State University, OARDC Extension


  About Toni Leland  
Toni LelandToni Leland has been writing for over 20 years. As a spokesman for the Ohio State University Master Gardener program, she has written a biweekly newspaper column and is the editor of the Muskingum County MG newsletter, Connections; she currently writes for GRIT, Over the Back Fence, and Country Living magazines. She has been a gardener all her life, working soil all over the world. In her day job, she scripts and produces educational DVDs about caring for Miniature Horses, writes and edits books about them, and has published five novels.

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