Identifying the Worst Weeds and the Best

Virginia creeper weed vine climbing over wooden structure

The Spruce / Margot Cavin

For the action-oriented, gawking at weed identification pictures may seem rather lame. Perhaps as far as they are concerned, they simply don't like a particular "volunteer plant" in the lawn or garden and are ready to go pull it up or spray it with an herbicide. They will not "dignify" the plant by identifying it first, before locking horns with it.

What is wrong with such a disdain for identifying the enemy as a preliminary step to doing battle? Plenty, as you probably already realize if you're consulting the following lists of the worst and best (that is, beneficial) weeds. The most basic objection is that it helps to know something about what it is that you are fighting. Proper weed identification can be the gateway to knowledge that has been compiled over the years regarding a particular plant.

Yes, as superficial as a mere name may seem, without it, you are barring yourself from all kinds of helpful tips and warnings. The purpose of this guide is not only to help you identify common lawn and garden weeds through photos but also to introduce you to some of those helpful control tips.

Often, we approach control from a position of ignorance. For example, the misinformed may confuse one colonizing plant with another and dub a loathsome nuisance encroaching upon a garden "sumac" when, in fact, it is Japanese knotweed. Why is it important to learn its true identity? The reason is that there's an impressive body of literature out there on Japanese knotweed control that can help you fight this menace intelligently.

One point that speaks volumes in favor of first identifying your enemy is the fact that not all herbicides are equally effective against all weeds. If you neglect to identify a weed properly prior to spraying it, you may be wasting time/money and causing unnecessary harm to the environment. To counteract such an exercise in futility, a discipline named "IPM" has arisen.

Also, by studying up on the plant first, you may discover facts about it that will alter your approach in fighting it (for instance, see below for poison ivy). And in some cases, garden weed identification may even altogether alter your desire for eradication of a particular plant as you discover its good qualities. Remember a "weed" remains a weed only so long as you consider it undesirable. For that reason, the following resources discuss not only plants that are commonly and justifiably found on homeowners' "hit lists," but also relatively innocuous plants whose designation as "weeds" you may wish to reconsider.

The 8 Worst Weeds

But there is nothing innocuous about the group of eight weeds listed below. The first three are especially noxious because they actually pose health risks. The fifth (Japanese knotweed) may cause more headaches than any other on the list. If you are unlucky enough to be gardening on a plot adjacent to a stand of Japanese knotweed, guarding against incursions from this infamous thug becomes nothing short of a way of life.

  • Poison ivy: Poison ivy can cause more than just an annoying itch. Did you know that you can develop serious health problems from attempting to eradicate poison ivy by burning the vines? And as commonly as one hears people speaking of poison ivy, proper weed identification for this plant is not as common as one might think. Many people needlessly spray the vine, Virginia creeper, thinking it is poison ivy. Worse yet, many others fail to identify the poison ivy that they encounter when enjoying outdoor activities--walking blindly into it and paying the price afterward.
  • Poison oak: If you live on the West Coast of the U.S., that "itchy vine" in your backyard may well be poison oak, not poison ivy.
  • Poison sumac: Of the "big three," poison sumac is not as widely encountered as its two relatives, poison ivy and poison oak. You will probably encounter it only if you landscape near swampy land. But it can give you just as bad a rash.
  • Crabgrass: Crabgrass will not harm your health, but it is an eyesore. The common lawn and garden weed, crabgrass, has a very name that suggests how tenacious a foe it is (think of a crab lodged in a crevice and stubbornly refusing to come out). You can tackle crabgrass before you spot it, or after it's already starting to take hold in your garden.
  • Japanese knotweed: The aforementioned Japanese knotweed may be the most widely detested plant that nobody has ever heard of. Japanese knotweed typically takes over areas of a property where the soil has been disturbed. This perennial weed forms dense stands of bamboo-like canes. So what is the problem? The problem is when cold weather comes, and the plants die, the unattractive dead canes remain left behind. In fact, it can take years for them to break down, thus creating an unsightly and unmanageable mess on your landscape. Do you have this problem in your own yard? Here is some help:
  • Common ragweed: Even the plant world has its scapegoats. The goldenrod weed is commonly blamed for causing "hay fever." But goldenrod is merely a victim of circumstance: It just happens to bloom at the same time of year as the ragweeds. It is ragweed that is truly responsible for the discomfort allergy sufferers feel every fall. Yet relatively few people can identify this inconspicuous plant. In many cases, those allergic to common ragweed pass it every day in the autumn, without giving it a second thought. Inconspicuous or not, it causes suffering for untold millions every fall. 
  • Giant ragweed: Common ragweed has a big brother, named "giant ragweed." Giant ragweed may appear to be a gentle giant, but it is no more innocuous than is its little brother, common ragweed.
  • Oriental bittersweet vines: There is not one, not two, but three plants referred to as "bittersweet." Confusing, isn't it? Those who wish to grow a bittersweet in North America are best off growing American bittersweet, not out of a sense of patriotism, but because it is well-behaved in its native land. By contrast, Oriental bittersweet is invasive in North America. Avoid it at all costs. While colorful, it will climb into the treetops and deprive specimen trees of adequate sunshine. It can also harm trees by girdling them. Oh, and the third kind of bittersweet? That is a tomato relative called "bittersweet nightshade," which produces toxic berries.

The 6 "Best" Beneficial Weeds

Beneficial types of weeds can merit such a classification based on various criteria, including the following:

  • Beauty
  • Ability to attract wildlife
  • The fact that they are edible
  • Medicinal uses
  • Fragrance
  • Use in low-maintenance landscaping

Of course, as with anything else where there are "good guys" and "bad guys," there will not be universal agreement on these nominations for beneficial weeds. For instance, there are folks who see no redeeming value whatsoever in creeping charlie.

  • Sumac shrubs: Because they are native to North America, sumac shrubs are often taken for granted here. Worse yet, they are often disparaged for being aggressive spreaders. Consequently, they are sometimes labeled as weeds (even though we more commonly think of only smaller plants as being "weeds"). But sumac shrubs' vibrant fall foliage is truly one of the joys of autumn, and their seeds are an emergency food source for wild birds in winter.
  • Creeping Charlie: Massed together, creeping charlie's blossoms are more attractive than those of some ground covers sold commercially. The plant also has medicinal uses and, when crushed, is quite fragrant.
  • Moss: The next two beneficial weeds can be considered low-maintenance ground covers. If you're currently trying to eradicate these "weeds," you may wish to ask yourself why. The very presence of moss in your lawn sends a clear signal as to what your lawn is lacking. In some cases, it is simply sunshine that is lacking--a problem you may not be able to correct very easily. In other cases, you can easily enough supply the missing ingredient (e.g., fertilizer). But before you go through a lot of trouble, consider the possibility that moss may simply be the preferred ground cover for your "problem area." Should you rethink moss as a low-maintenance landscaping alternative to grass?
  • Clovers: Picture an ideal "carpet" of plants to be treading upon in an outdoor living space. Now describe your vision. What qualities make it so ideal? Surprisingly, it may be clover, not grass, that turns out to be the living carpet of your dreams. So why are you trying to get rid of this low-maintenance landscaping alternative to grass?
  • Dandelion weeds: The final two beneficial weeds that make the list offer the benefit of edibility. Like crabgrass, the dandelion is so common a lawn weed that most people need little weed-ID help to recognize it. Also like crabgrass, homeowners spend millions of dollars and countless hours every year trying to eradicate it from lawns. But that's where the similarities end. Dandelions are rather easy on the eye for the most part, and they are edible weeds: the nutritious greens can be harvested, cooked, and served at mealtime.
  • Purslane: While one cooks dandelion greens before serving them (to remove some of the bitterness), succulent purslane can just as easily be eaten raw in salads. It is trendy now to serve purslane at upscale restaurants, so why not save some money and eat your own at home?
The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Identifying Poison Ivy. University of Maryland Extension

  2. Poison Oak Management Guidelines. University of California Extension

  3. Poison Sumac. Colorado State University

  4. Crabgrass. University of Maryland Extension

  5. Common Ragweed. Michigan State University Extension

  6. Creeping Charlie: Is This Plant a Weed? University of Minnesota Extension

  7. Dandelion. Michigan State University Extension