What is a weed? And who decides what is a weed? Simply put, a weed is a plant out of place. Unfortunately, that makes weed identification difficult because there is not agreement on what is considered a weed. Farmers might argue that any plant they didn’t plant is a weed. Gardeners may disagree and enjoy the looks of bird-planted pokeweed with its bright purple berries, or the lovely pale pink blossoms of evening primrose. On the other hand, houttuynia that you planted may have overtaken the shrubbery and become a real pest. At that point, it is definitely a weed.
Most people would agree that anything that pops up in their grass is a weed. However, there is some benefit to identifying what those weeds are. For instance, these weeds indicate soil deficiencies:
- Low pH – sheep sorrel
- High pH – broadleaf plantain
- Compaction – goosegrass
- Low Nitrogen fertility – legumes (clover)
- Poor soil – quackgrass
- Poor drainage, moist soil – sedges
- Surface moisture – algae
Weed control is not easy. In the lawn, an herbicide may kill the grass along with the weed. Be sure to check the label to see if the herbicide is compatible with the lawn grass. In flower beds, grass may overtake desired plants, and you might want to use a product that kills grass. Organic gardeners commonly use 20% vinegar for annual weeds. Also, propane weed torches can super-heat plants and will kill annual weeds. Perennials, however, come back from the roots. And then there are sedges, the bane of many a gardener. Nutsedge is extremely resistant to almost every type of weed control. For those pesky weeds, the choice is to use the proper herbicide for the particular plant, or get a comfortable stool, a good attitude, and restore your soul by weeding after a rain.
Because annual weeds are easier to kill, knowing whether the weed is an annual or a perennial is helpful. For a list of common perennial and annual broadleaf weeds, visit the Aggie Turf site.
If you prefer pictures rather than drawings, type the scientific name followed by the word “image” into your search engine. Or search for the scientific name at the USDA Plants page.
This University of Illinois site helps identify weeds based on the plant’s characteristics.
For general information about weed control, check the Aggie Turf site.