Weeds Guide: 8 Types of Weeds and How They Affect Your Garden

A weed is a broad category describing an unwanted plant. Weeds can take on different forms and appear in a variety of landscapes, including gardens, farmland, and grass lawns.
For example, the term weed can be used to describe a pretty wildflower that begins to grow in a garden, as well as an invasive species that reproduces quickly to overtake a habitat.

Noxious weeds are plants that have been identified as harmful for agriculture, natural ecosystems, or humans. In most cases, noxious weeds are non-native species that arrive in new regions from crop shipments. Many noxious weeds grow from rhizomes, horizontal root structures, which promote the spread of the weed. Some noxious weeds are poisonous for humans, while others can deplete soil nutrients. Some examples of noxious weeds include bindweed, purslane, and creeping Charlie.

Some weeds are beautiful garden plants that help surrounding flowers and improve landscaping. Beneficial weeds can improve soil health, prevent pests, and grow edible flowers. For instance, nasturtium and plantain both bloom edible leaves and flowers. Nasturtium blooms bright orange flowers that are safe to eat, and plantain produces edible leaves that can be brewed for tea.

Weeds can improve or deplete your garden, depending on the extent of their growth. If left uncontrolled, invasive weeds can develop deep root systems that prevent new plants from growing. If kept under control, weeds can protect your soil from wind and rain erosion.

Some weeds can indicate a problem in the soil, as certain weeds grow when the soil lacks nutrients. For example, white clover grows in soil that is nitrogen deficient. This perennial weed transfers airborne nitrogen back into the ground, replenishing the soil. The deep taproots of lambsquarter, also known as pigweed, help bring water and nutrients to the top layer of the soil, nourishing plants with shallow roots. Finally, weeds can also restore biodiversity to your garden by adding organic matter to the soil when their leaves fall.

There are numerous types of weeds that require different forms of weed control. Understanding the differences between common weed varieties can help you identify and treat the weeds in your garden.

1. 1. Dandelion: Dandelions are one of the most common broadleaf weeds in the US. They first bloom bright yellow flowers, which eventually turn into the signature white, fuzzy seedlings that resemble the shape of a lollipop. Dandelions are perennial weeds, so they regrow every spring. To get rid of unwanted dandelions, simply pick the flowers from the root of the plant. If they continue to grow, you can try using a herbicide to kill the dandelions. Consistently mowing your lawn also prevents dandelions from growing in the grass.
2. 2. Henbit: Like dandelion, henbit is a broadleaf weed. Henbit typically starts to grow during sporadic warm periods during wintertime. The hotter temperatures of late spring and early summer often kill the weed. With improved lawn care, you can prevent henbit from growing.
3. 3. Thistle: There are different types of thistles from Canada thistle to musk thistle; however, all thistles are characterized by their spiny leaves. Thistles are classified as a noxious weed in various US states due to their ability to inhibit the growth of surrounding plants. One way thistles do this is by releasing chemicals into the soil. Covering the soil in mulch can help prevent thistles from growing. You can remove thistles from your yard by pulling them up from the roots or spraying a herbicide.
4. 4. Chickweed: One of many common lawn weeds, chickweed is found throughout North America. Chickweed thrives in moist soil, forming thick mats of dense leaves and small white flowers. Once chickweed starts to grow, it can be difficult to eradicate, taking as long as seven to eight years to fully remove. The best way to get rid of chickweed is to catch it early and pull the weed before germination. Chickweed is edible; you can eat the leaves and flowers raw or cooked.
5. 5. Knotweed: Knotweed is an annual common lawn weed that usually grows in overwatered areas and is characterized by its blue tinted, oval leaves. However, knotweed is a hardy weed that can tolerate dry soil as well. It starts to germinate in late winter and can establish a root system that continues to grow through summer and early fall. Weeding knotweed will help prevent it from spreading and taking over your garden.
6. 6. Nutsedge: Purple and yellow nutsedge are aggressive weeds that can reproduce quickly in adverse conditions. These weeds are difficult to control because most weed killers don’t target them. Nutsedge often appears due to poor soil drainage, so improving water drainage is the first step in removing them. Next, apply herbicides to the areas where nutsedge is growing to kill the weeds and protect turfgrass.
7. 7. Crabgrass: Crabgrass is a grassy weed that commonly grows in lawns. While it is a type of grass, it is not considered turfgrass. Crabgrass can dominate your lawn during the summertime, creating a thick ground cover. To prevent crabgrass, you can use a pre-emergent herbicide on your lawn. If crabgrass is already sprouting and spreading across your lawn, you can use a post-emergent herbicide to kill and stop it from spreading.
8. 8. Nettle: Nettles can be a perennial or annual weed. They’re known for quickly growing in large clumps of green leaves that can reach 4 feet tall. While nettles can attract butterflies, they can also overwhelm a garden. The stinging hairs on their leaves can harm surrounding plants. Keeping nettles under control by trimming the leaves or removing the roots altogether can help protect your garden.

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