Identifying Harmful Weeds in Your Garden

Updated July 18, 2018
Start by weeding any areas you plan to mulch. (Photo courtesy of Melissa Caughey/Tilly's Nest)

The definition of "weed" can vary, but weeds generally share characteristics that include persistence in growth, growing out of place without being intentionally sown, and interfering with the plants that are intentionally sown in the soil.

Weeds often grow with voracious energy, and they can even be harmful to humans and animals if touched or ingested. Weed seeds spread easily and may lie dormant for many years. Weeds also tend to thrive in poor soil, so they grow easily without cultivation. Identifying weeds in a home garden is the first line of defense because it's important to remove the weeds before they can reproduce or interfere with other plants. Some weeds are limited to particular growing regions, while others grow freely in virtually any environment. A savvy gardener will remain vigilant throughout the year to root out weeds if they appear in their home garden.

Visit these websites to learn about harmful weeds that may grow in a garden:

African Mustard: African mustard grows up to 3 feet in height and has small yellow flowers. This weed grows in sandy soil.

Bindweed: Bindweed climbs and creeps and has white flowers. Bindweed reproduces prolifically and can take over a growing area.

Class A Weeds (PDF): Class A weeds are non-native plants with a high rate of distribution. Examples of Class A weeds include dyer's woad and meadow clary.

Chinese Tallow: Chinese tallow is a tree that can grow to be up to 30 feet in height and spreads invasively in swampy areas and floodplain forests. Small yellow flowers appear on the tree in the spring.

Controlling Quack Grass in the Garden: Quack grass can quickly take over a garden or a lawn with its underground root system, long seed spikes, and tall stems.

Purslane: Weed it or Eat it? Purslane has a long taproot in the center of the plant, large leaves, and stems giving forth yellow blooms. Purslane seeds may remain viable in the soil for up to 40 years.

Invasive Weeds in Georgia: Tree of Heaven (PDF): Tree of heaven is a tree that may reach heights of up to 80 feet with trunks as wide as 6 feet across. Tree of heaven looks like a sumac, and it often grows in poor soil. This tree often takes over in growing areas, reproducing freely.

Identification and Control of Invasive Weeds in North Dakota: Absinth Wormwood and More (PDF): Absinth wormwood gives off a strong sage odor, and it can infest a growing area easily. Those with pollen sensitivities are often bothered by absinth wormwood, which has tall flower stalks and yellow flowers.

Weed Control for the Home Vegetable Garden: Common Lambsquarters (PDF): Lambsquarters can grow in many different growing areas, forming tiny green blooms and reproducing by seed. The leaves and stems may reach heights of up to 6 feet.

Noxious Weed Field Guide for Utah: Malta Starthistle (PDF): This thistle can grow up to 2 feet high, and it has stiff stems with sharp spines jutting out just beneath the yellow flowers.

Poison Hemlock Identification and Control: Poison hemlock is noxious and can be deadly to animals and humans. The hollow stalks may grow to be 8 feet or even higher, and the flowers bloom in clusters that resemble umbrellas.

Noxious Weed Species: Parrotfeather: Parrotfeather grows in aquatic areas, with some leaves emerging from the water and others growing beneath the surface. White flowers will appear on the stems.

Invasive Weed Field Guide: Giant Reed (PDF): This invasive grass may become as tall as 30 feet, and it grows in clumps. The leaves are long and pale green, and feathery plumes stand erect above the leaves.

Air Potato: The air potato creates a dense growth of vines that will become so thick that they choke out other plants. This plant has large leaves and a large, round seed pod.

Asiatic Sand Sedge: This invasive weed will grow about 1 foot in height and has stems in triangular shapes. The leaves are long and thin, and the flowering heads resemble a club.

Purple Loosestrife: Purple loosestrife features showy purple flowers, making it seem like a good addition to a home landscape. However, this plant spreads freely, and it will quickly take over a growing area.

Chinese Yam (PDF): Chinese yam is a fast-growing vine that produces bulbs that fall off and spread to reproduce the plant. Yellow-green blossoms smell like cinnamon.

Wild Parsnip: Wild parsnip can often be seen in fields as yellow-green clusters of blossoms. Touching wild parsnip can produce blisters on the skin.

Cordgrass (PDF): Cordgrass is an aquatic grass that grows in coastal areas. Tall stems and leaves produce tiny yellow flowers in clusters.

Butterbur Sweet Coltsfoot: This plant looks like rhubarb with big heart-shaped leaves and massive stalks. Tiny pink flowers come out in the spring before the leaves emerge.