Pennsylvania weeds (Here are the most common)

Pennsylvania is home to a wide variety of weeds that can be found in lawns, gardens, and natural areas. These weeds can be difficult to control and can quickly spread, causing damage to the surrounding vegetation.

Proper identification and management of weeds is essential to maintain the health and appearance of your lawn and garden. Understanding the characteristics and growth habits of common Pennsylvania weeds can help you develop an effective weed control strategy that works for your specific situation.

Pennsylvania weeds snippet

Table of Contents

Pennsylvania weeds

Name of weed Family
Black Medic Legume
Broadleaf Plantain Plantaginaceae
Bull Thistle Asteraceae
Chicory Asteraceae
Cinquefoil Rosaceae
Cornmint Lamiaceae
Crabgrass Poaceae
Dandelion Asteraceae
Dead Nettle Lamiaceae
Dogbane Apocynaceae
Fern Dennstaedtiaceae
Ground Ivy Lamiaceae
Henbit Lamiaceae
Jimsonweed Solanaceae
Lambsquarter Amaranthaceae
Milkweed Apocynaceae
Morning-glory Convolvulaceae
Oxalis Oxalidaceae
Pigweed Amaranthaceae
Pineappleweed Asteraceae
Purslane Portulacaceae
Ragweed Asteraceae
Speedwell Plantaginaceae
Spotted Spurge Euphorbiaceae
Velvetleaf Abutilonaceae
Violet Violaceae
White Clover Apiaceae
Yarrow Asteraceae
Yellow Nutsedge Cyperaceae
Yellow Woodsorrel Oxalidaceae

Black Medic

Black medic is a small annual weed that can be identified by its yellow flowers and clover-like leaves. Although it has a shallow root system, it can spread rapidly if not controlled in time. Its deep roots can draw moisture from the soil, making it an ideal candidate for pre-emergent control against larger weeds like dandelions. Additionally, black medic can be easily removed from the soil when the ground is moist.

Type

Annual

Family

Legume

Control

Pre-emergent control is an effective method for preventing the growth of black medic and other weeds in areas where the weed has been eliminated. However, post-emergent herbicides may be necessary if black medic has already established itself. Regularly watering, fertilizing, and aerating the lawn can also help prevent the growth and spread of black medic and other weeds.

Black Medic

Broadleaf Plantain

Broadleaf plantain is a persistent and invasive weed that can quickly take over neglected lawns, particularly in moist areas with little sunlight. It forms flat rosettes with green, oval-shaped leaves and has a shallow but thick root system that can grow up to 18 inches long. This weed species thrives in compacted soil and is commonly found in disturbed areas such as agricultural lands, open fields, sidewalks, roadsides, and trails. It can tolerate both full sun and partial shade.

Type

Perennial

Family

Plantaginaceae

Control

To keep broadleaf plantain under control, it’s recommended to aerate the lawn in the fall to prevent compacted soil. Mowing the lawn at a higher height of 3-4 inches and seeding sparse areas can also help prevent the growth of this weed. However, if it does appear, using a broadleaf herbicide is an effective method for getting rid of it.

Plantain

Bull Thistle

Belonging to the Asteraceae family, Bull Thistle is a biennial weed that is frequently found in Kentucky. Known for its prickly leaves and purple flowers, this weed can grow up to six feet tall and has a taproot that can reach up to three feet deep. It is commonly found in disturbed areas such as fields, pastures, and roadsides.

Type

Biennial

Family

Asteraceae

Control

Controlling Bull Thistle can be challenging due to its deep taproot. One effective method is to hand-pull the weed before it goes to seed by grasping the base of the plant and removing the entire root. Alternatively, a selective herbicide can be used to target only Bull Thistle without harming other plants in the area. It’s best to apply the herbicide during the spring or fall when the plant is actively growing.

noxious weeds bull thistle

Chicory

Chicory, scientifically known as Cichorium intybus, is a perennial weed that belongs to the Asteraceae family. It’s typically found in Kentucky and can be recognized by its toothed leaves and blue flowers. Chicory can grow up to four feet tall and is commonly found in pastures, waste areas, and along roadsides.

Type

Perennial

Family

Asteraceae

Control

Chicory can be effectively controlled by using selective herbicides or hand-pulling before it goes to seed. Preventing its spread can be achieved by maintaining healthy turf, mowing before seeding, and monitoring new growth. These control measures are essential in managing the growth and spread of Chicory.

growing chicory

Cinquefoil

Potentilla recta, commonly known as cinquefoil, is an annual weed of the rose family that can grow up to 2 feet tall. It blooms in late spring with bright 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, cinquefoil can become an aggressive species and outcompete native vegetation for resources.

Type

Annual

Family

Rosaceae

Control

When removing sulfur cinquefoil manually, it’s important to exercise caution as it can spread rapidly through root fragments or wind-dispersed seeds. Effective control can be achieved by using herbicides containing glyphosate, 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.

Sulfur cinquefoil

Cornmint

Cornmint, also known as field mint, is a perennial weed that belongs to the Lamiaceae family. It has a square stem and can grow up to 3 feet tall. Cornmint produces small, white to pink flowers in the summer. This weed is commonly found in agricultural fields, pastures, and along roadsides.

Type

Perennial

Family

Lamiaceae

Control

Controlling Cornmint requires a combination of cultural and chemical control methods. Cultural control involves preventing seed production by mowing or hand-pulling the weed before it flowers. Chemical control involves using herbicides such as 2,4-D, dicamba, or glyphosate.

These herbicides are most effective when applied in the fall or early spring when the plant is actively growing. Overall, controlling Cornmint requires a combination of methods, including proper lawn maintenance, herbicides, mowing, and hand-pulling.

Cornmint

Crabgrass

Crabgrass is a low-growing weed that spreads horizontally, resembling a crab’s legs. It has flat, green leaves that point outward and finger-like florets, with spreading and branched stems. Its roots develop at the nodes on prostrate stems.

Crabgrass thrives in dry and hot conditions and is commonly found in disturbed areas such as weedy meadows, prairies, lawns, gardens, fields, vacant lots, grassy paths, and along roads and railroads.

Type

Annual

Family

Poaceae

Control

Regularly mowing the lawn is an effective way to control the growth and spread of crabgrass. Additionally, applying a pre-emergent herbicide in the spring when the weed is actively growing is the best way to prevent it from taking hold in a lawn or garden. The herbicide should be sprayed to cover the entire area.

crabgrass stems

Dandelion

Dandelions are a hardy perennial garden weed that can withstand freezing temperatures. The dandelion blooms emerge from a single stem, and its flat, spear-shaped leaves produce a milky sap. Seed heads can be seen emerging from the flowers, which children often pluck and blow across the garden, causing the weed to quickly spread its seeds.

Dandelions prefer acidic soils and are challenging to control due to their far-reaching seed pods, which can sprout hundreds of new shoots.

Type

Perennial

Family

Asteraceae

Control

Yarrow is a fast-growing broadleaf weed that can be identified by its flat-topped clusters of white flowers. The leaves are greyish-green in color and have three to five leaflets with sharply serrated edges. Yarrow has a strong scent, which makes it easy to identify when it blooms in the summer and early autumn.

Dandelions

Dead Nettle

Dead Nettle, also known as Lamium, is a perennial weed that belongs to the Lamiaceae family. It has heart-shaped leaves and produces flowers that range in color from pink to purple. Dead Nettle grows well in moist, shady areas and is commonly found in gardens, lawns, and other landscaped areas.

Type

Perennial

Family

Lamiaceae

Control

Controlling Dead Nettle can be achieved through a combination of manual and chemical methods. Manual control involves hand-pulling the weed or using a hoe to remove it from the soil. Chemical control involves using herbicides that contain glyphosate or triclopyr. 

These herbicides should be applied when the plant is actively growing. Additionally, maintaining a healthy lawn through proper watering, fertilization, and aeration can help prevent the growth and spread of Dead Nettle. Regularly mowing the lawn can also help reduce the weed’s growth.

Deadnettle

Dogbane

Belonging to the Apocynaceae family, Dogbane is a perennial weed commonly found in Kentucky. Also known as Indian hemp, American hemp, and rheumatism weed, this plant can grow up to 2 meters tall and is frequently branching. 

It grows in colonies, with a woody base. While the fiber from the bark was used by Native Americans to make rope, Hemp Dogbane is a poisonous herb.

Type

Perennial

Family

Apocynaceae

Control

Hemp Dogbane is resistant to many herbicides, making its control challenging. Glyphosate in Roundup Ready corn is the most effective approach, while Glufosinate can suppress it in LibertyLink crops. Selective broadleaf herbicides such as fluroxypyr and dicamba are somewhat effective in conventional corn, but hand-pulling can be time-consuming. 

Overall, controlling Hemp Dogbane requires a combination of methods, including proper lawn maintenance, herbicides, and aggressive hand-pulling.

Dogbane

Fern

Fern weed, also known as bracken fern, is a perennial weed that belongs to the Dennstaedtiaceae family. It can grow up to 6 feet tall and has triangular fronds that resemble a fern. Fern weed is commonly found in wooded areas, open fields, and along roadsides. It is a highly invasive species that can quickly take over an area if left unchecked.

Type

Perennial

Family

Dennstaedtiaceae

Control

Controlling Fern weed can be challenging due to its extensive root system. Manual removal by digging up the roots is an effective method for small infestations. However, for larger areas, chemical control is necessary. Herbicides such as glyphosate, triclopyr, and imazapyr are effective in controlling Fern weed. 

These herbicides should be applied during the growing season when the plant is actively growing. Additionally, monitoring new growth and promptly removing any new plants can help prevent the spread of Fern weed.

bracken fern

Ground Ivy

Ground Ivy is a fast-spreading perennial broadleaf weed that can quickly take over large areas in lawns. It can be identified by its kidney-shaped leaves and small, purple flowers. When crushed or mowed, the weed emits a distinct sweet smell. Ground Ivy typically invades damp, shady areas where turf growth is weak, and its stems have a four-sided appearance with a fuzzy texture.

Type

Perennial

Family

Lamiaceae

Control

Removing Ground Ivy from your lawn can be challenging due to its aggressive growth habit. To effectively control this weed, it’s recommended to regularly mow the lawn as short as possible and use post-emergent herbicides to spot-treat the weeds. Applying pre-emergent herbicides can also be helpful.

young ground ivy

Henbit

Henbit is an annual broadleaf weed with a low-growing habit that can rapidly spread and take over areas in lawns with weak turf during the growing season. The weed has oval leaves with serrated edges and produces purple tubular flowers. Henbit can grow up to 16 inches tall, thanks to its fibrous root system. Its reddish-purple flowers have dark spots on the lower petals and typically germinate in early fall or winter.

Type

Annual

Family

Lamiaceae

Control

Roundup is effective in controlling Henbit, but it should only be applied during the weed’s active growth period. Maintaining a healthy lawn through regular watering and fertilization is the best way to control Henbit. Using pre-emergent herbicides can also prevent new weeds from germinating.

Henbit

Jimsonweed

Jimsonweed is a biennial weed with a tall, erect growth habit and angular, prickly leaves. It is commonly found in open fields and lawns and can quickly spread if not controlled. This weed species has prickly stems covered with small white hairs and large, spiky leaves that are pale green or purplish-green in color. Its flowers are trumpet-shaped and typically white or purple.

Type

Biennial

Family

Solanaceae

Control

For effective control of this weed, consider using selective broadleaf herbicides like 2,4-D (in various formulations). Alternatively, you can use tank mixtures containing both 2,4-D and either dicamba (Weed Master) or triclopyr (Crossbow).

Jimsonweed

Lambsquarter

Lambsquarters is an annual weed with a low to medium growth habit and small, white flowers. It is commonly found in gardens and lawns, where it can rapidly spread if not controlled. This weed species has diamond-shaped leaves that are smooth on the upper surface and whitish beneath, as well as small greenish-white flowers that are grouped together in clusters.

Type

Annual

Family

Amaranthaceae

Control

To effectively control Lambsquarters, selective broadleaf herbicides like 2,4-D or dicamba (Weed Master) can be used. If physical removal is preferred, ensure to remove all parts of the plant, including its roots.

Lambsquarters

Milkweed

Common Milkweed, a perennial weed from the Apocynaceae family, is found in Kentucky and is characterized by large leaves and clusters of pink or purple flowers. To control it, prevention is key. Maintaining healthy turf or crops, mowing before it goes to seed, and regular monitoring to catch new growth are effective methods.

Type

Perennial

Family

Apocynaceae

Control

Common Milkweed can be challenging to control due to its deep and extensive root system. An effective method is to use a selective herbicide that targets only the weed in its early stages of growth. 

Hand-pulling the weed before it goes to seed and ensuring the entire root is removed is another method. However, it’s essential to note that Common Milkweed is an important plant for pollinators, so complete eradication may not be desirable.

Common Milkweed

Morning-glory

Morning-glory is an annual vine that belongs to the Convolvulaceae family. It is a fast-growing weed that can quickly take over gardens, lawns, and other landscaped areas. Morning-glory has heart-shaped leaves and produces trumpet-shaped flowers that range in color from white to purple. The weed is often found in sunny areas with well-drained soil.

Type

Annual

Family

Convolvulaceae

Control

Controlling Morning-glory can be challenging due to its rapid growth and extensive root system. Manual control involves pulling the weed out of the ground, being sure to remove the entire root system. Chemical control involves using herbicides such as glyphosate or triclopyr. 

These herbicides should be applied when the plant is actively growing. Additionally, maintaining a healthy lawn through proper watering, fertilization, and aeration can help prevent the growth and spread of Morning-glory. Regularly mowing the lawn can also help reduce the weed’s growth.

Morning Glory

Oxalis

Oxalis is a small plant that typically grows up to 5 cm tall. It has dark purple or green leaves and produces tiny yellow flowers. Although it looks attractive, if left unchecked, it can quickly multiply and spread throughout an area. Larger, less invasive varieties of Oxalis are often sold as houseplants.

Type

Perennial

Family

Oxalidaceae

Control

For spot-treating Oxalis, a non-selective herbicide containing glyphosate is ideal, especially in landscape beds. It’s essential to ensure that the glyphosate spray thoroughly wets the foliage of the weeds. Targeting the seedlings and young plants yields the best results.

Oxalis

Pigweed

Pigweed, also known as Amaranthus retroflexus, is an annual weed that belongs to the Amaranthaceae family. It is widespread in gardens, croplands, and disturbed areas throughout Kentucky. Pigweed can grow up to 6 feet tall and is characterized by green or red diamond-shaped leaves. It produces small green flowers that later develop into numerous tiny seeds.

Type

Annual

Family

Amaranthaceae

Control

To control Pigweed effectively, it’s essential to combine various methods. Preventing seed production is crucial for successful weed control. Applying herbicides such as glyphosate, 2,4-D, or dicamba to actively growing, small Pigweed can be effective. 

For small infestations, hand-pulling can also be useful, although it can be time-consuming for larger areas. Proper lawn maintenance, herbicides, and hand-pulling are all necessary methods to control Pigweed effectively.

pigweed

Pineappleweed

Pineappleweed is an annual weed with yellow-green leaves and small, pineapple-scented flowers. It is typically found in dry, sandy soils or open fields and prefers areas with high light exposure. Without proper monitoring or control, Pineappleweed can rapidly spread.

Type

Annual

Family

Asteraceae

Control

Pre-emergent herbicides like trifluralin (Treflan) or pendimethalin (Pendulum) are the most effective way to control this weed. For post-emergent control, products containing glyphosate (Roundup) can be used.

Pineappleweed

Purslane

Purslane, also known as Portulaca oleracea, is a leafy green vegetable with red stems, small green leaves, and an impressive 93% water content. It can be enjoyed raw or cooked in various dishes and is also known by other names such as pigweed, little hogweed, fatweed, and pusley.

Many consider it a weed, but it is a healthy and nutritious plant. Purslane is rich in omega-3 fatty acids, containing more than any other leafy vegetable. It is also a good source of vitamins B and C, iron, magnesium, calcium, and potassium.

Type

Annual

Family

Portulacaceae

Control

Purslane can be eliminated through manual extraction or chemical control methods. Conserving soil moisture through rainfall and irrigation can reduce its spread. In addition, broadleaf herbicides such as 2,4-D or dicamba (Weed Master) can effectively control it.

Purslane

Ragweed

Ragweed is a common and unpleasant weed found in lawns. This tall, annual weed has long stems with small, yellowish-green flowers that produce lots of pollen, which is a significant cause of hay fever and allergies. Ragweed thrives in warm, sunny areas such as roadsides, fields, gardens, and lawns. As its seeds are dispersed by wind or animals, it can easily spread from one area to another.

Type

Annual

Family

Asteraceae

Control

The best way to control ragweed is through prevention. Regular mowing can prevent the plant from growing too tall and going to seed. Hand-pulling can be effective when the plant is young, but it’s essential to dispose of the weeds properly as ragweed can easily re-sprout.

Ragweed

Speedwell

If you’ve noticed a weed with a purple hue in your lawn, it could be Speedwell. This creeping annual thrives in cooler and more humid soils in Ohio that are shaded from direct sunlight. With its light blue to purple flowers and round leaves with scalloped edges, identifying this pest is relatively easy, even for novice gardeners.

Type

Annual

Family

Plantaginaceae

Control

To control Speedwells, specific broadleaf weed herbicides can be applied successfully. These herbicides are designed to target and eliminate individual plants, as well as any seeds produced, to prevent the weed from spreading further throughout your lawn. When applying these herbicides, it’s crucial to follow the directions on the label carefully and avoid overapplication.

Speedwell

Spotted Spurge

Spurge is a warm-season weed that commonly appears in container nurseries. It produces greenish-white flowers and a milky sap when its leaves or stems are broken. Ground spurge and spotted spurge are two types of spurge that have similar appearances, with prostrate to ascending stems carrying oblong or round leaves. Spurge can be found in various locations, including grasslands, pastures, roadsides, and prairies. It is adaptable to various soil types, making it a common sight in many areas.

Type

Perennial

Family

Euphorbiaceae

Control

For a small patch of spurge, hand-pulling can be an effective method to remove it. However, prevention is the best method to deal with this weed since controlling it can be challenging once it has taken root. Various post-emergent herbicides can be used to control spurge invasions in gardens or lawns. It’s crucial to apply the herbicide when the weed is actively growing for maximum effectiveness.

Spotted spurge

Velvetleaf

Velvetleaf, also known as buttonweed, is an annual weed that grows in clumps of broad, velvety leaves. This low-growing weed can quickly overtake a garden or lawn if not adequately controlled. It produces yellow flowers with four petals that form at the tips of long stalks, which later become seedpods.

Type

Annual

Family

Abutilonaceae

Control

The most effective way to control velvetleaf weed is by pulling them by hand. It’s crucial to do so before they mature and go to seed since the seeds can remain viable in the soil for up to 25 years. Pre-emergent herbicides like Treflan or Preen can also be used to prevent velvetleaf from germinating. Additionally, post-emergent herbicides such as 2,4-D, triclopyr, or Glyphosate may be used for existing plants.

Velvetleaf

Violet

Wild Violets are a type of perennial weed with heart-shaped leaves and small flowers that can range in color from purple and blue to white. These weeds tend to grow low along the ground and prefer moist soil conditions.

Type

Annual or Perennial

Family

Violaceae

Control

Controlling Wild Violets can be challenging due to its spreading underground roots. To prevent these weeds from growing, use a pre-emergent herbicide in early spring or fall. Additionally, regularly mowing your lawn can help keep it healthy and strong enough to outcompete invasive weeds like Wild Violets.

Wild Violets

White Clover

White clovers can be recognized by their white, puffy blooms and leaves that generally have a pale white “V” on them. This weed species grows low to the ground and can quickly cover an entire lawn. White clover is active during spring, summer, and autumn and thrives in lawns that are deficient in nitrogen.

Type

Perennial

Family

Apiaceae

Control

Proper lawn maintenance is essential to prevent white clover from growing and spreading. A pre-emergent herbicide application is recommended to control the invasion of white clover. To eradicate established weeds, it’s important to use a post-emergent herbicide application.

early fall white clover

Yarrow

Yarrow is a broadleaf weed that grows rapidly. You can identify this weed by its flat-topped clusters of white flowers. The leaves are greyish-green in color and have three to five leaflets with sharply serrated edges. Yarrow has a strong scent, making it easy to identify the weed when it blooms in summer and early autumn.

Type

Perennial

Family

Asteraceae

Control

Preventing the growth of yarrow is the best approach to control this weed species. If you notice any yarrow starting to grow, it’s crucial to remove them before they spread their seeds. A pre-emergent herbicide application can also be used to prevent new yarrow plants from sprouting. For existing yarrow weeds, a post-emergent herbicide application is the most effective solution.

Woolly Yarrow (Achillea tomentosa)

Yellow Nutsedge

Yellow Nutsedge, also known as Cyperus esculentus, is a perennial weed from the Cyperaceae family. It is native to North America and can be commonly found in lawns and gardens throughout Kentucky. This weed can grow up to 3 feet tall and has yellow-green leaves and brown seed heads that resemble spikes.

Type

Perennial

Family

Cyperaceae

Control

Yellow Nutsedge can be challenging to control due to its extensive root system and ability to re-grow from small root pieces in the soil. The best approach is to use a combination of cultural and chemical control methods. Cultural control involves improving soil drainage and reducing watering frequency. 

Chemical control involves using selective herbicides like sulfentrazone, halosulfuron, or imazaquin. Hand-pulling can also be effective for small infestations, but it should be done with caution as all parts of the plant are poisonous.

Yellow Nutsedge

Yellow Woodsorrel

Yellow woodsorrel, also known as Oxalis stricta, is a North American perennial weed from the Oxalidaceae family. It can be found in lawns, gardens, and waste areas. This weed can grow up to 12 inches tall and has small, yellow flowers that bloom from May to September.

Type

Perennial

Family

Oxalidaceae

Control

To manage Yellow woodsorrel, it’s crucial to remove it before it goes to seed. This can be done by hand-pulling or using a hoe to cut the stem below the soil surface. Mulching can also help to suppress growth and prevent seed germination. If chemical control is necessary, herbicides containing dicamba or 2,4-D can be effective.

Yellow woodsorrel
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Oliver Wright
Oliver Wright

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