Oregon is home to a variety of weeds that can be a nuisance to homeowners, gardeners, and farmers alike. These weeds can be invasive, fast-growing, and difficult to control. They can also outcompete native plants and disrupt the local ecosystem.
Some of these weeds are annual, while others are perennial, making it challenging to manage them effectively. Understanding the different types of weeds found in Oregon and their growth habits is essential in developing a comprehensive weed control strategy.
Proper identification and timely control measures can help prevent the spread of these weeds and maintain the health of the local environment.
Table of Contents
Minnesota weeds
| Name of weed | Family |
|---|---|
| Black Medic | Legume |
| Bull Thistle | Asteraceae |
| Canada Thistle | Asteraceae |
| Chickweed | Caryophyllaceae |
| Dandelion | Asteraceae |
| English Ivy | Araliaceae |
| Garlic Mustard | Brassicaceae |
| Giant Hogweed | Apiaceae |
| Himalayan Blackberry | Rosaceae |
| Hoary Cress Whitetop | Brassicaceae |
| Horsetail | Equisetaceae |
| Japanese Knotweed | Polygonaceae |
| Poison oak | Anacardiaceae |
| Puncturevine | Zygophyllaceae |
| Purple Loosestrife | Lythraceae |
| Scotch broom | Fabaceae |
| Spotted Knapweed | Asteraceae |
| Spurge Laurel | Thymelaeaceae |
| Toadflax | Plantaginaceae |
| Yellow Starthistle | Asteraceae |
Black Medic
Identified by its yellow flowers and clover-like leaves, black medic is a small, low-growing annual weed with a shallow root system. While easily pulled out of the soil, it can spread quickly if not controlled. Its deep roots make it an effective defense against larger common weeds such as dandelions, and it is often used for pre-emergent control to prevent other oregon noxious weeds from germinating in areas where black medic has been eliminated.
Type
Annual
Family
Legume
Control
Hand removal of this weed can be highly effective when the soil is moist, as it is easier to pull out its roots. Undertaking this task during damp conditions can increase the chances of success. Alternatively, a herbicide application can also be used to control black medic.
Bull Thistle
Bull Thistle, a biennial weed, is frequently found in Kentucky and belongs to the Asteraceae family. It is recognized for its prickly leaves and purple flowers, and can grow up to six feet tall with a taproot that extends up to three feet deep. Bull Thistle is typically found in disturbed areas such as pastures, roadsides, and fields.
Type
Biennial
Family
Asteraceae
Control
The deep taproot of Bull Thistle makes it difficult to control. Hand-pulling the weed before it goes to seed is an effective method, ensuring the entire root is removed. Another option is to use a selective herbicide that targets Bull Thistle without harming other plants in the area. The herbicide should be applied in the spring or fall when the weed is actively growing.
Chickweed
Chickweed is a creeping winter weed that grows in lawns and gardens. The weed’s seeds germinate in cool temperatures and quickly take root, allowing it to overgrow large areas. Chickweed can be identified by its mat-like foliage on the ground and small white flowers. It thrives in moist areas and is challenging to control due to its potential to spread rapidly.
Type
Annual
Family
Caryophyllaceae
Control
Preventing chickweed from taking root is the best way to keep it from growing in your lawn. To prevent its growth, it is recommended to avoid overwatering the lawn and raise the mower blade, particularly during the autumn season.
Dandelion
Dandelions are a well-known lawn weed with bright yellow flowers. The leaves are deeply notched, toothy, and hairless, forming a rosette above the central taproot. When the bright yellow flower heads mature, they turn into white puffballs containing seeds. Due to their deep and aggressive root system and quick germination capabilities, dandelions are challenging to control.
Type
Perennial
Family
Asteraceae
Control
Hand-pulling the entire plant from the soil is an effective method of controlling small dandelion infestations. For established plants, applying weedkiller in autumn can help eliminate them permanently. Correctly applied post-emergent applications can also help prevent their spread.
English Ivy
English Ivy is an invasive perennial vine that belongs to the Araliaceae family. It is native to Europe but has become naturalized in many parts of North America. English Ivy can grow up to 100 feet long and has woody stems with dark green, glossy leaves. This weed species can climb trees and buildings, causing damage to structures and outcompeting native plant species.
English Ivy is a highly invasive and competitive weed species that can cause significant damage to structures, agriculture and natural habitats. Its ability to climb and spread rapidly makes it challenging to control. Therefore, a combination of cultural, mechanical, and chemical control methods is necessary to manage this weed effectively.
Type
Perennial
Family
Araliaceae
Control
Effective methods of controlling English Ivy include a combination of cultural, mechanical, and chemical control methods. Cultural methods include manually removing the weed and planting native groundcovers in its place. Mechanical control methods involve cutting the vine at the base and removing it from trees or buildings. Chemical control methods include the application of herbicides such as glyphosate and triclopyr.
Garlic Mustard
Garlic mustard is a biennial weed that can grow up to three feet tall. In early spring, the roots and new leaves give off a garlic-like scent. The kidney-shaped leaves become smaller toward the top of the stem, and the small white flowers have four petals, four sepals, and six stamens.
Once established, Garlic mustard is difficult to control. It is tolerant of both sun and shade and outcompetes native vegetation. Additionally, it has a high seed production rate, making it challenging to eliminate completely.
Type
Biennial
Family
Brassicaceae
Control
Hand-pulling is an effective method for controlling garlic mustard because even mature plants can be easily removed. However, it is important to ensure that all of the roots on larger plants are dug out. Spot spraying herbicides in the spring and autumn is also effective in controlling garlic mustard invasion.
Giant Hogweed
The giant hogweed is aptly named, as it can grow up to 14 feet or more in height. It features large, white, umbrella-shaped flowers in clusters that can reach up to 2.5 feet wide. This invasive species species is a well-known public health hazard, as it contains a clear, watery sap that is toxic and can make the skin extremely sensitive to the sun. If the sap comes into contact with the eye, it can cause temporary or even permanent blindness.
The giant hogweed thrives in rich, damp soil and is commonly found along ditches, roadsides, vacant farmlands, streams, and rivers. It is primarily found in urban areas, with 70% of all giant hogweed sites located in urban environments.
Type
Perennial
Family
Apiaceae
Control
Spot spraying with a herbicide containing glyphosate during the budding or active growth stage is highly effective in controlling this giant weed. However, it is important to follow label instructions carefully and use caution to avoid harming non-target plants.
Himalayan Blackberry
Himalayan blackberry is a perennial weed that belongs to the Rosaceae family. This noxious weed species is native to Armenia and Northern Iran and was introduced to North America in the late 1800s. Himalayan blackberry is characterized by its thorny stems, which can grow up to 40 feet long, and its large, edible blackberries. This weed can quickly take over an area, outcompeting native vegetation and causing significant damage to the ecosystem.
Type
Perennial
Family
Rosaceae
Control
Effective methods of controlling Himalayan blackberry include physical and chemical control methods. Physical control methods include hand-pulling, cutting, and mowing the weed. Chemical control methods involve the use of herbicides such as glyphosate and triclopyr.
Hoary Cress Whitetop
Hoary Cress, also known as Whitetop, is a perennial weed that belongs to the Brassicaceae family. This weed species is native to Europe and Asia and was introduced to North America in the late 1800s. Hoary Cress is characterized by its small, white flowers and grayish-green leaves that form a basal rosette. It can grow up to three feet tall and has a deep root system that makes it challenging to control.
Hoary Cress is a highly invasive weed species that can cause significant damage to natural habitats and agricultural lands. Its deep root system and ability to spread rapidly make it challenging to control. Therefore, a combination of chemical and physical control methods is necessary to manage this troublesome weed effectively.
Type
Perennial
Family
Brassicaceae
Control
Effective methods of controlling Hoary Cress include the use of herbicides and physical control methods. Chemical control methods involve the use of herbicides such as glyphosate and 2,4-D. Physical control methods include hand-pulling, cutting, and mowing the weed. However, it is important to follow label instructions carefully and use caution to avoid harming non-target desirable plants.
Horsetail
Horsetail, also known as Equisetum, is a perennial weed that belongs to the Equisetaceae family. This weed species is characterized by its jointed stems that resemble horse tails and can grow up to three feet tall. Horsetail is a well-known invasive plant species that can be found in damp, marshy areas, and disturbed soils. It is known for its aggressive growth and ability to spread quickly.
Type
Perennial
Family
Equisetaceae
Control
Methods of controlling Horsetail include physical and chemical control methods. Physical control methods involve hand-pulling and digging out the weed. Chemical control methods involve the use of herbicides such as glyphosate and imazapyr. However, it is important to follow label instructions carefully and use caution to avoid harming non-target plants.
Japanese Knotweed
Japanese knotweed is easily identifiable by its white flowers emerging from pink buds and reddish-purple shoots. The weed species can grow through piping, cables, buildings, and foundations, eventually causing extensive damage to the property. It blooms best in late summer and early autumn. Once established, Japanese knotweed is challenging to control.
Type
Perennial
Family
Polygonaceae
Control
Professional guidance is recommended for controlling Japanese knotweed. Approved herbicides can be used to prevent its spread, but it can take up to three years to completely treat the weed.
Poison oak
Poison oak, also known as Toxicodendron diversilobum, is a perennial weed that belongs to the Anacardiaceae family. This weed species is native to North America and is commonly found in wooded areas, along roadsides, and in fields. Poison oak is known for its leaves, which contain urushiol, a toxic oil that can cause an itchy rash when it comes into contact with the skin.
Type
Perennial
Family
Anacardiaceae
Control
Physical control methods involve hand-pulling and digging out the weed. Chemical control methods involve the use of herbicides such as glyphosate and triclopyr. However, it is important to follow label instructions carefully and use caution to avoid harming non-target plants.
Puncturevine
Puncturevine, also known as Tribulus terrestris, is an annual weed that belongs to the Zygophyllaceae family. This weed species produces small yellow flowers on low-growing plants and can be found in sandy or gravelly soils throughout North America. Puncturevine has long, narrow leaves with pointed tips and oval seedpods that contain sharp spines, which can puncture tires and other materials.
Type
Annual
Family
Zygophyllaceae
Control
Small infestations of puncturevine can be manually removed by digging up the entire root system from the soil. Herbicides containing dicamba or triclopyr are effective at controlling this weed species and should be applied to actively growing plants. Additionally, spot treatment of glyphosate can be used to target individual weeds. It is important to regularly monitor the area to ensure that puncturevine does not return.
Purple Loosestrife
Purple loosestrife is an erect plant that can grow up to 3-10 feet tall. Its square and sometimes woody stem bears bright purple flowers in long spikes. This weed species forms dense mats of roots and can spread over large areas, crowding out natural vegetation and reducing biodiversity. A single plant can produce millions of tiny seeds that are dispersed by wildlife, water, and wind.
Type
Perennial
Family
Lythraceae
Control
For small areas infested with purple loosestrife, cutting, hand-pulling, and digging can be effective methods of control. Spot treatment with approved herbicides is also recommended.
Scotch broom
A weed species that can be recognized by its bright, small yellow flowers in the leaf axils is known to grow in dry, sandy soils and full sunlight. The stems are green and have sharp angles with small leaves growing in groups of three.
It is commonly found in meadows, clearings, and forest edges, and can survive in various soil conditions. Its seeds have the ability to remain viable for almost 80 years. This weed species is called Scotch broom.
Type
Perennial
Family
Fabaceae
Control
While small Scotch broom plants can be manually removed by pulling them out when the soil is moist, a systemic herbicide is necessary for effective control of this weed. This is because the plant has the ability to produce new shoots from cut roots, stems, and stumps. To ensure complete eradication, it is important to use a herbicide that can kill the entire plant.
Spotted Knapweed
The spotted knapweed is a weed species that can grow up to three feet tall from a sturdy taproot. Its basal rosettes produce deeply lobed grey-green leaves, while its branches bear solitary pink-purple flower heads. This weed prefers well-drained soils and only spreads through its seeds. It is commonly found along Alaska’s roadsides and is known to cause severe environmental damage and economic loss.
Type
Biennial or short-lived perennial
Family
Asteraceae
Control
Controlling the invasion of spotted knapweed is a challenging task. The recommended method to remove this weed is to hoe, pull, or dig it out two to four times per year. To prevent resprouting, it is crucial to cut the weed at least two inches below the root crown.
Spurge Laurel
Spurge Laurel, also known as Daphne laureola, is a perennial weed that belongs to the Thymelaeaceae family. It is native to Europe and is commonly found in woodland areas throughout Kentucky. Spurge Laurel can grow up to 6 feet tall and has glossy evergreen leaves and small yellow-green flowers that bloom from February to April.
Type
Perennial
Family
Thymelaeaceae
Control
Controlling Spurge Laurel can be challenging due to its extensive root system and tolerance to many herbicides. The best approach is to use a combination of cultural and chemical control methods. Cultural control involves manually removing the plant and its roots. Chemical control involves using selective herbicides such as glyphosate, 2,4-D, or dicamba.
These herbicides are most effective when applied in the fall or early spring when the plant is actively growing. Overall, controlling Spurge Laurel requires a combination of methods, including proper lawn maintenance, herbicides, and manual removal.
Toadflax
Dalmatian toadflax (Linaria vulgaris) is a perennial weed species that originated from Europe and Asia. It can grow up to 2 feet tall and produces yellow flowers with long and narrow leaves. The plant has an extensive root system and can quickly spread as it can reseed itself, making it a challenging weed to control. Its flowering period is from July to October.
Type
Perennial
Family
Plantaginaceae
Control
When dealing with Dalmatian Toadflax, manual removal is recommended if possible. However, for larger infestations, using an appropriate herbicide can help control its growth. Always wear protective gear and follow label instructions when handling herbicides. Mowing can also be effective, but it must be done regularly before the weed goes to seed. Proper disposal of the removed weeds is crucial in preventing further spread and re-growth.
Yellow Starthistle
Yellow starthistle, a member of the Asteraceae family, is an annual weed that can grow up to 3 feet tall. It blooms in early summer with yellow flowers and prefers dry and well-drained soil. This weed is commonly found in disturbed areas such as abandoned fields and roadsides. If not controlled, yellow starthistle can become an aggressive species and outcompete native vegetation for resources.
Type
Annual
Family
Asteraceae
Control
It’s important to exercise caution when manually removing yellow starthistle as it can spread rapidly through root fragments or wind-dispersed seeds. Effective control can be achieved by using herbicides containing dicamba or triclopyr, which should be applied to actively growing plants. Spot treatment with glyphosate can also be used to target individual weeds. Mowing the plant before it flowers can help reduce seed production.
