Identify Weeds By Photo: 117 Common Weeds by Photo

What Is a Lawn Weed and What Is a Garden Weed?

Lawn weeds and garden weeds aren’t necessarily distinct, as any unwanted plant which grows in the lawn may be considered a lawn weed and any unwanted plant growing in a garden is likely to be called a garden weed.

Weeds can grow anywhere that conditions are favorable, but certain types of weeds are more likely to thrive in lawn versus garden settings.

Lawn weeds are often plants that are low-lying and not greatly impacted by mower blades. Many Grassy weeds and Grass-Like weeds will pop up along the edges of lawns or in bare spots, as they prefer tightly packed soil.

They can usually tolerate moderate foot traffic. Many lawn weeds are members of the Sedge or Grass families, monocots with dense fibrous roots.

Then what is a garden weed? Garden weeds are typically plants that thrive in disturbed or loosened soil.

They may be volunteers from a previous year’s crops or opportunists who found a place to set down roots.

Garden weeds are a very diverse group of plants. They can often grow to a significant height and may be Vining, Woody, or Herbaceous.

Garden weeds are found in a wide range of families which are often eudicots with deep-anchored taproots.

32 Types of Common Lawn Weeds (With Picture and Name): Identification Guide

Many types of weeds can be seen in a lawn, from Grassy weeds such as Crabgrass and Orchardgrass, to Grass-Like weeds such as Onion Grass and Lilyturf, to Low-Lying Broadleaf weeds such as Dandelion, Ground Ivy, and Clover.

* USDA State Noxious-Weed Seed Requirements Recognized in the Administration of the Federal Seed Act. ‘Noxious’ indicates federal listing. Other listings include state abbreviations.

31 Types of Common Garden Weeds (With Picture and Name): Identification Guide (Identify Weeds by Photo)

Garden weeds come in many different forms, and most fall under the Broadleaf type of weeds.

Many garden weeds, such as Butterweed and Fleabane, are members of the Daisy family (Asteraceae), or the Carrot family (Apiaceae), like Poison Hemlock and Queen Anne’s Lace.

(Image: GoranH⁴⁴)

* USDA State Noxious-Weed Seed Requirements Recognized in the Administration of the Federal Seed Act. ‘Noxious’ indicates federal listing. Other listings include state abbreviations.

United States Noxious Weeds

There are currently more than 100 plants listed on the USDA’s Federal Noxious Weed List and many more listed by individual states on the USDA 2022 State Noxious-Weed Seed List. For example, although Canada Thistle (Cirsium arvense) is not listed as a federal noxious weed, it is a prohibited weed seed in the majority of states across the U.S. The U.S. Forest Service provides field guides for dealing with some of the most persistent weeds.

Being able to identify noxious weeds is crucial to protecting a balanced ecosystem, so check both of these lists to learn about federally noxious weeds and those which are considered noxious at the state level!

Other United States Common Types of Weeds (With Picture and Name): Identification Guide

When weeds are common, identify weeds by photo may seem like an easy task, but many common weeds are difficult to differentiate. Luckily, there are some excellent resources for anyone seeking to learn more about invasive, noxious, and native troublesome weeds in their area.

(Image: JosepMonter⁵⁰)

* USDA State Noxious-Weed Seed Requirements Recognized in the Administration of the Federal Seed Act. ‘Noxious’ indicates federal listing. Other listings include state abbreviations.

Identify Colorado Weeds by Photo

Aside from federally listed noxious weeds, each state has its own array of problematic weed species, which can be explored in depth via the USDA 2022 State Noxious-Weed Seed List. Colorado’s beautiful landscape is home to a wide variety of weed species.

Troublesome weeds are designated as List A, B, C, or Watch List species (most to least problematic), according to the Colorado Department of Agriculture.²³ Use the table below to learn about some common weeds of Colorado and access links to identify Colorado weeds by photo.

What Are Weeds?

A weed has been defined in many ways by different people, and it seems that the true definition of a weed lies in the eye of the beholder. The term ‘weed’ is subjective, and what is considered a weed by one person or group may not be considered a weed in other circumstances.

Some individuals consider any wildflower or uncultivated plant a weed while others consider only foreign plants weeds and still others identify weeds by looking at their morphological characteristics. So how close can an individual come to answering the question “What are weeds?” with a precise definition?

(Image: PhotoAC⁵³)

Though the word ‘weed’ is neither a biological nor technical term, it may be assigned to a plant bearing particular characteristics or exhibiting certain behaviors. The most general definition describes a weed as any plant growing in a place where it is not desired.¹

Many are curious about how many types of flowers are there which are considered weeds or weedy. One estimate suggests that there are roughly 8,000 species of weeds that can be classified according to some more specific behaviors commonly associated with weeds, such as:^13,22

• The ability to establish a community quickly
• Aggressive spreading
• Over-production of seeds
• Longevity of buried or dormant seeds
• The ability to thrive in less-than-ideal environments or disturbed soils

They may also have:

• Unattractive or over-abundant foliage
• Less pronounced flowers
• A negative impact on nearby plant species

Related Reading: 232 Types of Flowers: How To Identify and Grow Flowers In Any Season

Invasive Weeds Versus Noxious Weeds

The most troublesome weeds are typically those which are invasive and noxious. The terms ‘invasive’ and ‘noxious’ are often used interchangeably in discussions of weeds although they are distinct.

According to the U.S. Bureau of Land Management, an invasive weed is any plant that is growing in its non-native habitat while a noxious weed is one which has been declared injurious due to its aggressive nature. Many noxious weeds are invasive, as invasive species have fewer competitors and inhibitors and can reproduce unchecked.¹

The United States Department of Agriculture (USDA) has instituted the program Animal and Plant Health Inspection Service (APHIS) to document, control, and prevent the introduction of invasive plant species. From this initiative, a Federal Noxious Weed List was developed which lists the plant species which pose the greatest threat to North America’s native flora.^7,24

Types of Weeds

There are many types of weeds; in fact, thousands and thousands of weeds make the list of undesirables, whether because of their appearance, behavior, or deleterious effect on the world around them.

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Weeds are often classified according to their life cycles (annual, biennial, or perennial), their status (native, beneficial, invasive, noxious, etc.), their location (lawn weeds, garden weeds, farm weeds), and their morphological characteristics (Broadleaf weeds, Grassy weeds, Sedges, etc.). The following sections explore morphological categorization in more detail.^{9, 19, 35}

Broadleaf Weeds

Broadleaf weeds make up the most diverse group of weeds. These types of weeds are eudicots, meaning that they develop from a cotyledon with two seed leaves.

Broadleaf weeds typically have wider, rounder leaves than grasses, and their leaves have a central vein with many peripheral veins branching outward. Broadleaf weeds may have fibrous roots, taproots, or both, and some species exhibit secondary growth via underground rhizomes or surface stolons.

The flowers of Broadleaf weeds tend to be more pronounced than those of the other weed classes.^{30, 31, 33}

(Image: Hans⁵⁴)

Many of the most familiar weeds are Broadleaf weeds, such as the Dandelion (Taraxacum officinale), Pigweed (Amaranthus retroflexus), Shepherd’s Purse (Capsella bursa-pastoris), and White Clover (Trifolium repens). There are many Broadleaf weeds on the USDA Federal Noxious Weed List, with the Mesquite genus (Prosopis) making up the largest group.

Grassy Weeds

Although Grassy weeds and Sedges are sometimes lumped together due to their surface appearance, they are two separate groups. Grasses and ‘grass-like weeds’ comprise the much larger group with several taxonomic families represented.

These types of plants are monocots (cotyledon bearing a single seed leaf). Their stems are typically round and hollow, and their leaves are often long and narrow with parallel veins.

Grassy weeds have fibrous root systems which may creep and produce secondary growth through rhizomes or stolons. There are both perennial and annual Grassy weed species.

True grasses are members of the Poaceae family, such as Annual Bluegrass (Poa annua), Crabgrass (Digitaria sanguinalis), Dallisgrass (Paspalum dilatatum), and Quackgrass (Elymus repens). Other grassy weeds may be representatives of the Iridaceae, Commelinaceae, and Liliaceae families, among others.

(Image: Bat⁵⁵)

There are several grassy weeds on the USDA Federal Noxious Weed List such as the African natives’ Velvet Fingergrass (Digitaria velutina) and Missiongrass (Cenchrus polystachios) and the U.S. native Liverseed grass (Urochloa panicoides).^{17, 30, 32}

Sedges

Sedges, like grasses, are monocots, and they are phenotypically very similar to grasses. They are distinguished by their solid, triangular stems.

Sedges are typically perennial plants with narrow, flat, parallel-veined leaves and fibrous, creeping roots that may exhibit secondary growth through rhizomes or tubers (discussed in the next section). Examples include the Nutsedge (Cyperus) and Bulrush (Scirpus) general.

(Image: bonniesherbals⁵⁶)

All Sedges are members of the Cyperaceae family, and no Sedges are currently listed on the USDA Federal Noxious Weed List.^{30, 31, 34}

Woody and Vining Weeds

The categories mentioned above are commonly accepted weed types, but there are many Broadleaf weeds that have distinct characteristics that set them apart. Most such examples are likely considered part of a subgroup of Woody and Vining weeds.

(Image: NPS photo by Alessandra Puig-Santana48)

Many perennial plants are capable of forming woody plant tissue over time, and this is most commonly seen in trees, shrubs, and vines. Some common examples include Poison Ivy (Toxicodendron radicans), Wild Blackberry (Rubus fruiticosus), Mesquite (Prosopis), and Honeysuckle (Lonicera periclymenum), which are very difficult to eradicate as they can easily regrow from root crowns or basal stems.^36,37

Types of Weed Roots

The root of a plant is the most essential piece of its anatomy, in terms of a plant’s ability to grow and survive. The root systems of plants are typically located under the surface of the earth, where they provide support for the organism and branch in various directions to acquire water and nutrients for the plant.

Types of weed roots generally fall into one of two primary categories: Fibrous roots and Taproots.¹²

Fibrous Roots

Fibrous roots are usually plentiful, branching out broadly beneath the surface of the soil. These root systems are adept at finding moisture and nutrients for the plant organism while also providing structural support.

Fibrous roots are commonly found in ferns, grasses, and many flowering plant species, such as Butterweed (Packera glabella). The roots are typically delicate and may break away easily.

Weeds with a fibrous network of roots are more easily pulled.¹²

Taproots

Taproots are characterized by a large, central root that anchors downward, often deep into the ground, with tendrils of smaller roots extending from the sides of the taproot. Taproots are commonly found in root vegetables such as beets, turnips, and carrots, as the dominant center root in these species grows and stores carbohydrates over time.

Dandelions (Taraxacum officinale) are a common Taproot weed, and many gardeners have discovered how difficult it can be to extricate Taproot plants. Weeds will frequently regrow if fragments of the taproot are left intact underground.¹²

Other Root Characteristics

Though Fibrous and Taproot systems are the most common, plant (and weed) roots do not always fit cleanly into one of these groups, as they may have characteristics that suit both or neither. Root systems have also developed interesting abilities over time, represented in the following, non-exhaustive list of specialized root characteristics.

Adventitious Roots

The Virginia Department of Forestry defines Adventitious roots as those which develop on a part of the plant other than the root, often in reaction to strain or stress. Adventitious roots can form from bulbs, stems, and tubers and can provide an advantage over less flexible root systems.¹⁶

They can be seen at the base of corn stalks, providing extra support, or on vines attached to tree trunks.² In some cases, adventitious roots form in response to injury.

Adventitious roots may also take the form of rhizomes, stolons, or tubers, horizontal stems which grow outward from the crown of the plant to aid in nutrient storage and/or asexual reproduction.²⁶

Contractile Roots

Contractile roots are commonly seen in plants that grow from bulbs or corms. They are called Contractile roots due to their ability to pull the plant parts deeper underground for protection from the elements and animals.

The roots often die back in winter and resprout in spring with fibrous root bundles at their base and thicker contractile roots interspersed.¹²

Bulbs have fleshy, layered skin while corms tend to be smaller, harder, and non-layered. Bulbous plants include flowers such as Tulips (Tulipa) and Hyacinths (Hyacinthus orientalis), vegetative plants such as Onion (Allium), and weeds such as Onion Grass (Allium vineale) and Wood Sorrel (Oxalis).

Corms include flowers such as the Crocus (Crocus tommasinianus) and Gladiola (Gladiolus). The terms are not mutually exclusive as a single organism may have multiple characteristics.¹⁵

Aerial Roots

Some plants are epiphytes (plants that grow on other plants) with Aerial roots which attach to the host organism (tree, bush, etc.) and absorb water from the air. These plants are not parasitic, but rather opportunistic, using their host to grow in higher places and access limited resources.

Common examples include Spanish Moss (Tillandsia usneoides) and several other members of the Bromeliaceae family.^5,12

Haustoria

Epiphytes are sometimes confused with parasitic plants which use modified roots (haustoria) to leech nutrients directly from the host organism. Well-known examples of parasitic plants include the beloved American Mistletoe (Phoradendron leucarpum) as well as the noxious Witchweed (Striga asiatica).¹²

10 Ways To Prevent Weeds Before They Become a Problem

Every gardener has wondered how to get rid of weeds, likely when weedy plants begin to overgrow vegetative and cultivated plant varieties in their garden beds. Luckily, there are some basic tips for weed control that work fairly well, particularly when the weeds are identified and addressed in a timely fashion.³⁵

The top 10 ways to prevent weeds before they become a problem are listed here!^14,28

1. Get familiar with your state’s common weeds, invasive weeds, and troublesome weeds to facilitate quick identification (see Bureau of Land Management Weed Control Strategies for state resources).
2. Do not till the entire garden area; work up the soil only where desired species will be planted. Minimize digging as much as possible to prevent surfacing weed seeds.
3. Consider using ground cloth and mulch in flower beds to cut back on the number of weeds.
4. Plan the garden bed so that the available space will be used up by desired plants.
5. Do not over-water or fertilize. Try to water desired plant roots rather than the entire garden area.
6. Pull shallow weeds or dig up taproot weeds when they are small. Maintenance is crucial! Discard weeds after pulling.
7. Use cornmeal gluten to prevent weeds from seeding (Sprinkle after desired plants have sprouted).
8. Spray salt and vinegar mixture or rubbing alcohol mixture on weeds to burn the foliage and destroy the weed over time.
9. Pour boiling water on weeds to scald them.
10. Use clear plastic to solarize (cook) a very weedy area.

Related Reading: Natural Homemade Weed Killer DIY With 3 Ingredients (Kills Weeds Permanently)

Beneficial Weeds

Some plants which are commonly considered weeds in a person’s lawn or garden may be very beneficial in some environments. In fact, many weeds were introduced deliberately for their medicinal or herbal value.

Common examples with a rich history of practical use include Dandelions, Violets, and Ground Ivy which can be found in many yards in early spring, as well as St. John’s Wort and the Heal-All plant.²⁵ Red clover (Trifolium pratense) is frequently grown on farmland during the off-seasons due to its nitrogen-rich composition which fuels the next round of food crops.¹²

Queen Anne’s Lace, the Wild Carrot (Daucus carota) might be best known for its prickly seed casings which can be found stuck to animal fur and clothing during fall and winter months, but many parts of this plant are edible and nutritious.^6,10

Weeds, as a class of plant organisms, are not all bad. This is why it is so important to identify weeds by photo and determine which weeds are actually dangerous to native flora.

Are There Chemical-Free Ways To Get Rid of Troublesome Weeds?

There are ways to get rid of troublesome weeds without using harmful chemicals if the problem is addressed promptly and correctly. Many weeds can be eliminated by pulling, digging up the root system, or smothering with mulch and ground cloth.

Other methods may include using vinegar, rubbing alcohol, baking soda, boiling water, salt, or cornmeal to kill weedy plants.^4,21

What Are the Most Noxious Weeds?

The most noxious weeds are typically those which are not native, spread aggressively, and use chemical warfare against neighboring plants. Some may even be parasitic like the Root-Parasitic Witchweed (Striga).

(Image: NPS photo by Alessandra Puig-Santana⁵²)

Many species of Mesquite (Prosopsis) and several types of grass are also quite noxious.¹¹

The Importance of a Balanced Ecosystem

Oftentimes, when people consider the impact of climate change, deforestation, and habitat destruction, they think of pollution and the ozone layer, endangered animal species, and declining tree populations.

Increasing knowledge about forest carbon offsets and using an individual carbon footprint calculator are incredible tools to combat these effects! It can be easy to overlook how important a role the hundreds of thousands of non-tree plant species also play in maintaining ecosystem stability.

It’s difficult to truly grasp the significance of native plant populations and the disproportionate weight they carry in the balance of the ecosystem. The role of plants goes beyond their abilities to prevent soil erosion, oxygenize the air, and their medicinal and nutritive values.

Plants maintain a symbiotic relationship with many organisms like pollinators and birds and fungi and support the entire ecosystem by providing food sources for the smallest herbivores on up. Biodiversity is crucial to ensuring species’ survival, and plants are among the most diverse group of organisms on the planet.^{5, 8, 18}

Of the hundreds of thousands of flowering plant species currently known, there are close to 10,000 species commonly considered to be weeds. Although weeds can have many benefits in native biomes, they can threaten native flora and fauna when introduced from other habitats.

This article explores some of the most common weeds in the U.S., including those that are harmful or noxious. It is extremely important to be able to identify weeds by the photo to eliminate or restrict noxious weed populations!

Frequently Asked Questions About Identify Weeds by Photo