Maine’s landscapes and diverse climate are perfect for several plant varieties, making the region susceptible to invasive species.
As such, Maine has many common weeds, ranging from garden weeds to invasive plants in crop fields, roadsides, and undisturbed areas.
You must first learn to identify these weeds to deploy the right control measures to fight them.
Below is a list of common weeds in Maine, their photos, identifying features, and top ways to eradicate them.
1. Canada Thistle (Cirsium arvense)
- Local Name: Canadian thistle; Creeping thistle; Cursed thistle
- Family: Asteraceae
- Annual or Perennial: Perennial
Canada thistle (California thistle, corn thistle, field thistle, or prickly thistle) is a rhizomatous herbaceous plant that grows to 0.3-1.5m tall.
It has slender, grooved stems that are smooth or occasionally covered with soft hairs.
The leaves are dark green, oblong, alternately arranged, and directly attached to the stems. The basal leaves reach 12-20cm long.
They also have lobed or toothed margins, short white hairs on the underside, and sharp, prickly spines along the margin.
The plant produces several attractive purple flowers that bloom at the top of branching stems. The flowers are tubular and covered with green bracts with hints of purple with weak spines.
It is native to:
- Europe
- Western Asia
- Northern Africa
NOTE: Despite the name, Canada thistle is not native to Canada. Instead, it is a widely distributed species in the North American region.
Removal methods
- Mechanical control: When the soil is moist, you can hand-pull or dig out young plants. Repeated tillage, mowing, and cutting can prevent seeding, reducing and eventually eradicating infestations.
- Chemical control: The plant can be eradicated with selective herbicides like 2,4-D, MCPA, dicamba, Bentazon, Clopyralid, chlorsulfuron, and dichlobenil. Non-selective herbicides like glyphosate are also very effective for large infestations.
2. Bird Vetch (Vicia cracca)
- Local Name: Cow vetch; bird vetch; tufted vetch; boreal vetch
- Family: Fabaceae
- Annual or Perennial: Perennial
Bird vetch is a perennial climbing plant that can grow to 1m (sometimes 2m) tall.
Its weak, hairy stems have noose-like branched tendrils that fasten around other plants for support and can easily suffocate smaller plants.
It has gray-green, alternate, and pinnate leaves. Each leaf has 8-12 pairs of small (5-10mm long) ovate leaflets with short hairs, a smooth margin, and a rounded to abruptly pointed tip.
The plant produces conspicuous, pea-shaped violet flowers, which grow in clusters (one-sided) along a raceme that rises out of the leaf axils in the upper stems.
It also bears a flattened pea pod containing 2-8 round or oval-shaped seeds.
Vicia cracca is native to Asia and Europe. However, it is widely distributed worldwide, including in North America.
Removal methods
- Mechanical control: Hand-pulling and regular mowing when the plants are young can prevent seeding. When performed regularly, these practices can diminish small infestations.
- Chemical control: Systemic herbicides like glyphosate and clopyralid effectively eradicate bird vetch. Other effective herbicides include 2,4-D and triclopyr.
3. Spiny Sowthistle (Sonchus asper)
- Local Name: Spiny sowthistle or Spiny-leaved sowthistle
- Family: Asteraceae
- Annual or Perennial: Annual
Spiny sowthistle (prickly show-thistle, rough milk thistle, or sharp-fringed sow thistle) is an erect, annual (sometimes biennial) plant that can grow 100-150cm tall.
It has green to reddish, stout stems, which are hairless, hollow inside, and release a milky sap when broken.
Sonchus asper has glossy, bluish-green leaves that are simple, alternately arranged, lanceolate in shape, and lobed with margins.
The leaf blades can reach 10 inches long by 3.5 inches wide and are covered with spines at the margins and the undersides.
The plant produces gold to yellow flowers that emerge from the leaf axis at the tip of the stem. Each flower head contains several yellow ray florets with no central disc.
It is native to:
- Europe
- North Africa
- Asia
Removal methods
- Mechanical control: Small infestations can be pulled out by hand when the plants are young and before seeding. Repeated mowing, tillage, and cutting shoots can prevent seeding and overwhelm spiny sowthistle.
- Chemical control: The weed can be eradicated using various chemical herbicides, such as 2,4-D, diuron, isoxaben, atrazine, glyphosate, Picloram, oxyfluorfen, paraquat, and others.
4. Field Bindweed (Convolvulus arvensis)
- Local Name: Morning glory
- Family: Convolvulaceae
- Annual or Perennial: Perennial
Field bindweed (creeping jenny or perennial morning glory) is a rhizomatous climbing or creeping plant that grows to 0.5-2 meters long.
It has weak, intertwining stems that are usually prostate, creating a thick ground cover.
Convolvulus arvensis has arrow-shaped, spirally arranged leaves attached to the stems by a short petiole. The leaf blades are 2-5cm long and have a lobed base, pointed tip, and an entire margin.
It also produces showy, white (or pink) trumpet-shaped flowers that bloom in the summer.
The flowers have two tiny bracts with a smooth surface (or fine hairs) and resemble those of true morning glory, hence the common name.
Convolvulus arvensis is native to Europe and parts of Asia. However, it is a widely distributed species in North America.
Removal methods
- Mechanical control: Small patches of young plants can be pulled out by hand. Repeated cutting can also control the plant and gradually diminish the infestation.
- Natural control: Natural remedies like solarization, boiling water, and vinegar-soap solution can be effective against small patches of young plants.
- Chemical control: Glyphosate is the most effective method of eradicating field bindweed. Other effective herbicides include dicamba, 2,4-D, Picloram, paraquat, and quinclorac.
5. Cypress Spurge (Euphorbia cyparissias)
- Local Name: Cypress spurge; Graveyard moss; Graveyard weed; Bonaparte’s crown
- Family: Euphorbiaceae
- Annual or Perennial: Perennial
Cypress spurge is a low-growing perennial herb with erect stems reaching 20-40cm in height. It has branching stems and can spread aggressively using a rhizomatous root system, forming a thick, bushy ground cover.
It has narrow (4cm long by 1-2mm wide), needle-like, blue-green leaves arranged in a spiral pattern around the stem. The leaves have an entire margin and, when broken, release a milky sap toxic to the skin.
The plant produces showy, bright yellow flowers that bloom in clusters at the stems tips. Each flower has two yellowish-green, round to heart-shaped bracts resembling petals.
Euphorbia cyparissias is native to Europe. It was introduced to North America as an ornamental plant but is now considered a noxious invasive species in many regions.
Removal methods
- Mechanical control: Hand-pulling or digging out is effective when dealing with small, new infestations. The soil should be moist for the best results, and protective equipment should be worn to protect against the toxic milky sap.
- Cultural control: Cultural practices like mulching, proper fertilization, and keeping desired plants healthy can control or prevent Cypress spurge infestation.
- Chemical control: You can eradicate the weed using chemical herbicides like 2,4-D, dicamba, and quinclorac (applied at the flowering stage) or Picloram (applied at full bloom or during the re-growth stage).
6. Purple Loosestrife (Lythrum salicaria)
- Local Name: Purple Loosestrife
- Family: Lythraceaea
- Annual or Perennial: Perennial
Purple loosestrife (purple Lythrum or spiked loosestrife) is an erect-growing perennial herb that can reach 0.5-2.0m in height. It has four-angled, smooth, or hairy stems and a strongly developed taproot system.
The plant has simple, opposite, lanceolate, dark-green leaves with an entire margin. The leaf blades are stalkless and grow to 3.8-10.2cm long.
From mid-late summer, the plant produces attractive, deep pink, purplish flowers that form in clustered spikes at the tip of the stems. Individual flowers have about 5-7 tiny petals and 10-14 stamens.
It is native to:
- Europe
- Asia
- North Africa
- Australia
It was introduced in North America as an ornamental plant and accidentally through contaminated soil used for ship ballast.
Removal methods
- Mechanical control: Hand-pulling and digging can be effective for small infestations of young plants. Mowing, plowing, and cutting can also control the weed, provided this is done before the plant starts seeding.
- Biological control: Galerucella pusilla (a leaf-feeding beetle), Galerucella calmariensis (a leaf-feeding beetle), and Hylobius transversovittatus (a root-mining weevil) are used as biological control agents for purple loosestrife.
- Chemical control: Glyphosate and Triclopyr are effective at eradicating the plant. Other herbicides, like 2,4-D and imazapyr, can eliminate the weed plant.
7. Common Yellow Woodsorrel (Oxalis stricta)
- Local Name: Yellow woodsorrel; common yellow oxalis; lemon clover
- Family: Oxalidaceae
- Annual or Perennial: Perennial (sometimes annual)
Common yellow woodsorrel is perennial and grows up to 23cm tall. It has several smooth (or slightly hairy) stems that emerge from the base of the plant and can either grow upright or sprawl on the ground.
It has light-green alternately arranged trifoliate leaves that resemble those of clover. Each leaflet is heart-shaped, about 2cm wide, and folds upward in half during the night or when stressed.
The plant has bright yellow flowers with five petals that form an open cup shape. From mid-spring to fall, the flowers bloom individually or in small clusters of up to five.
It also bears capsule fruits that look like tiny okra pods, which are hairy and ribbed. The pods open up explosively when mature, dispersing tiny, brown seeds.
It is native to:
- North America
- Europe
- Asia
Removal methods
- Mechanical control: Young plants can be hand-pulled or dug up before seeding. This should be done when the soil is moist to ensure complete plant removal, including the root rhizomes.
- Chemical control: It can be eradicated using post-emergent herbicides like glyphosate, sulfentrazone, isoxaben, flumioxazin, and indaziflam. Pre-emergent herbicides can also prevent the emergence of new plants from the seeds or rhizomes.
8. Annual Ragweed (Ambrosia artemisiifolia)
- Local Name: Common ragweed; short ragweed
- Family: Asteraceae
- Annual or Perennial: Annual
Annual ragweed (common ragweed, bitterweed, hay fever weed, or blackweed) is a summer annual plant that grows up to 6 feet tall. It has erect, branching, hairy, light pink to red stems.
It has compound, fern-like, toothed, and deeply lobed leaves that measure about 4-10cm long. The leaves, oppositely arranged on the stem, are hairy when young but become smooth as they age.
From late summer, the plant starts producing inconspicuous green flowers in slender, long spikes that turn yellowish or brown.
The male flowers release massive amounts of tiny yellow pollen that causes hay fever.
It is native to:
- Canada
- U.S.A
- Alaska
- South America (Brazil, Paraguay, Chile, Peru, Bolivia, Brazil, and Argentina)
- Cuba
- Jamaica
- Hispaniola
Removal methods
- Mechanical control: Hand-pulling or digging can be effective for small patches, but it is best done when the plants are young and before seeding. Repeated tillage (before seeding) can also control the spread of the weed.
- Biological control: Ophraella communa and Zygogramma suturalis, two species of ragweed leaf beetle, have been used to control common ragweed with very positive results.
- Chemical control: Herbicides like glyphosate, Metsulfuron, and glufosinate can eradicate the crop. However, repeated applications may be necessary when dealing with large infestations.
9. Hairy Galinsoga (Galinsoga quadriradiata)
- Local Name: Shaggy soldier
- Family: Asteraceae
Hairy galinsoga (shaggy soldier or Peruvian daisy) is an annual herb that grows 10-60cm tall. It has upright, branching stems, which are covered by dense hairs.
Its leaves ovate, oppositely arranged along the stem and with coarsely toothed margins. The leaves, like stems, are covered with dense hairs, giving them a velvety appearance.
The plant produces small flower heads that form at the tip of the stem from the leaf axils and can bloom in a clustered pattern.
Each flower head has a central disc of yellow florets surrounded by 4-5 white ray florets.
Galinsoga quadriradiata is native to Mexico. However, it is widely distributed in several other places, including:
- North America
- South America
- Europe
- Asia
Removal methods
- Mechanical control: Hand pulling and digging out can be effective for small patches of young plants. However, removed parts of the plant must be disposed of carefully as Galinsoga can re-root from cut stems.
- Cultural control: Cultural practices like crop rotation, use of cover crops, and mulching can help control the spread (or prevent encroachment) of the weed, but they cannot eradicate it.
- Chemical control: Galinsogacan can be eradicated using post-emergence herbicides like glyphosate, glufosinate, and diquat. Pre-emergence herbicides like flumioxazin and isoxaben can also control new germinations.
10. Shepherd’s Purse (Capsella bursa-pastoris)
- Local Name: Shepherd’s purse
- Family: Brassicaceae
- Annual or Perennial: Annual
Shepherd’s purse is an aggressive-growing annual plant in the mustard family that reaches 10-50 (and occasionally 70cm) in height. Its slender, green to purplish stems are covered by gray hairs.
The basal leaves of Shepherd’s purse grow in a rosette pattern (reaching 3-15cm long by 4cm wide), while upper leaves are arranged alternately on the stem.
The leaf blades are hairy and can be round to oval-shaped, smooth, toothed, or deeply lobed on the edges.
The plant produces small flowers with four rounded white petals and six yellowish-green stamens at the center.
The flowers bloom in clusters at the tip of the stems and later develop into flattened, triangular, heart-shaped seed pods containing several tiny seeds.
Capsella bursa-pastoris is native to Europe and parts of Asia. However, it is widely distributed worldwide, including in North America, South America, Asia, Africa, the Mediterranean, and Australia.
Removal methods
- Mechanical control: Hand-pulling and cultivation are effective on young plants before they seed.
- Cultural control: Mulching, crop rotation, and planting competitive beneficial crops can control the spread of Shepherd’s purse.
- Chemical control: It can be eradicated using post-emergent herbicides like Bentazon, flumioxazin, glyphosate, diquat, and flumioxazin. Pre-emergent herbicides like oxadiazon, pendimethalin, and oxyfluorfen can control new germinations.
11. Quackgrass (Elymus repens)
- Local Name: Couch grass; Quickgrass; Witchgrass
- Family: Poaceae
- Annual or Perennial: Perennial
Quackgrass is a perennial grass with rhizomatous roots that can grow to 40-150cm tall. It can be easily identified by the claw-like auricles that clasp around the stem.
It has alternate, ascending leaves that reach 12 inches long and 10mm wide. The leaf blades are flat, stiff, pointed at the apex, and sometimes covered with hairs on the upper surfaces.
The grass produces clusters of flowers that form on a single, erect spike at the tip of the stems.
Each spikelet is about 2-8 inches long and has two rows of greenish-blue flowers that turn into a tan straw color when dry.
It is native to:
- Europe
- Asia
- Northwest Africa
- The Arctic
Removal methods
- Mechanical control: When the soil is moist, young plants can be pulled from the ground (before seeding). Mature plants can also be dug out (from the rhizomes) using gardening tools, but this is very labor-intensive.
- Cultural control: Mulching, maintaining healthy lawns or beneficial crops, re-seeding of lawns, proper fertilization, and planting of cover crops can control the spread of Quackgrass.
- Natural control: You can kill infestations of Quackgrass by covering them with a plastic mulch or repeatedly burning them.
- Chemical control: It can be eliminated using glyphosate, atrazine, imazapyr, and grass-selective herbicides.
You can check out our quackgrass elimination guide for more methods in detail.
12. Lambsquarters (Chenopodium album)
- Local Name: Lambsquarters; White goosefoot
- Family: Amaranthaceae
- Annual or Perennial: Annual
Lambsquarters is a fast-growing plant in the Amaranth family that reaches 10-150cm in height. It has upright reddish to purplish stems with streaks of green that can be covered with sparse hairs.
It has dull green-bluish leaves that are toothed, opposite or alternately arranged, and varying in shape from triangle to diamond or lance-shaped.
The leaf blades vary in size, reaching 2-14cm long by 1-6cm wide, with the basal leaves larger than the upper ones.
The plant produces inconspicuous green flowers that bloom in clusters at the top of the stems. The flowers do not have petals and are covered with a powdery coat, just like the leaves.
Chenopodium album is native to Europe and Asia. It is also widely distributed worldwide, including in North America and countries like Nepal and India, where it is cultivated as a food crop.
Removal methods
- Mechanical control: You can hand-pull young plants before they start seeding. Repeated light tillage and cutting to the stem can also control the weed and eventually overwhelm the seed bank.
- Cultural control: You can control (but not eradicate) weeds through cultural practices like mulching, planting cover crops, and maintaining healthy, beneficial crops.
- Chemical control: Herbicides like 2,4-D, Aminopyralid, Chlorsulfuron, glyphosate, Hexazinone, imazapyr, paraquat, Picloram, and triclopyr are very effective at eradication.
13. Giant Hogweed (Heracleum mantegazzianum)
- Local Name: Giant hogweed; Giant cow parsnip
- Family: Apiaceae
- Annual or Perennial: Perennial
Giant hogweed is a perennial (sometimes biennial) herbaceous plant that grows 2-5m tall. Its hollow, green stems with purple specks are covered with coarse white hairs.
Its leaves are alternately arranged, with deep, irregular lobes and sharp, toothed margins. The leaf blades are large and can reach 1-1.5m long when mature.
The plant produces several tiny, clustered flowers at the stem’s tip, forming a compound umbel. The umbels are large, with each one reaching up to 2.5 feet wide.
Giant hogweed produces a clear, toxic sap, which reacts with sunlight when exposed to the skin, causing painful blisters. Therefore, despite its attractive flower blooms, it is one of the most noxious weeds in Maine.
The plant is native to some parts of Europe and Asia but widely distributed worldwide, including North America, New Zealand, and the United Kingdom.
Removal methods
- Mechanical control: Repeated cutting and mowing can prevent new seed formation and overwhelm the plant, depleting the seed bank and stored root reserves. However, this increases the risk of contact with the toxic sap.
- Cultural control: Sheep and cattle like grazing on the plant, and repeated intense grazing can overwhelm it, reducing infestation.
- Chemical control: Herbicides like glyphosate and triclopyr can eradicate giant hogweed. However, repeated treatments are needed to eliminate infestations.
14. Curly Dock (Rumex crispus)
- Local Name: Curly dock; Curled dock; Yellow dock; Sour dock; Narrow dock
- Family: Polygonaceae
- Annual or Perennial: Perennial
Curly dock is a perennial flowering plant that grows to 1.5 meters tall. It has upright, grooved stems with swollen nodes and hairy sheaths that form around the nodes.
It has large, dull-green basal leaves that can grow to 14-24cm long and are lanceolate with curvy margins. Conversely, the upper leaves are smaller, alternately arranged, and attached to the stem by a long petiole.
The plant produces clustered flowers at the tip of the stem, which tower over the foliage. The flowers, which lack petals, are greenish but turn reddish-brown when mature.
Rumex crispus is native to Europe and Asia. However, it is widely distributed in temperate regions of the U.S.A. and Canada.
Removal methods
- Manual control: Hand-pulling or digging out with gardening tools can effectively deal with young plants. However, the entire plant must be removed from the taproot, or it will regrow.
- Mechanical control: Repeated tillage, mowing, and cutting down the plant to the roots can prevent new seeding and gradually reduce the infestation.
- Cultural control: Mulching, improving draining, crop rotation, and planting cover crops can help control the spread of curly dock.
- Chemical control: Curly dock can be eradicated using various herbicides, such as 2,4-D, Aminopyralid, clopyralid, dicamba, Picloram, triclopyr, glyphosate, chlorsulfuron, Hexazinone, and sulfometuron.
15. Common Buttercup (Ranunculus acris)
- Local Name: Common buttercup; Tall buttercup; Tall crowfoot
- Family: Ranunculaceae
- Annual or Perennial: Perennial
Common buttercup is a perennial herbaceous plant that grows 30-100cm tall. Its green, hairy stems are hollow and heavily branched at the top.
It has mid-green, hairy leaves divided into 3-5 lobes, each with a toothed margin. The leaves are large, reaching 4 inches long and 6 inches wide.
The plant bears showy, glossy yellow flowers that form at the tip of the stem, rising from the leaf axils. Each flower has five to seven yellow petals and numerous yellow stamens at the center.
Although common buttercup is easy to spot in Maine, it is native to:
- Europe
- Far East Russia
- Greenland
- Aleutian Islands
Removal methods
- Mechanical control: Hand-pulling and digging can control small patches of Ranunculus acris. Frequent mowing and cutting the stems to the roots can reduce the weed’s vigor and prevent new seeding.
- Chemical control: It can be eradicated by spraying with herbicides like glyphosate, MCPA, Metsulfuron, dicamba, and aminopyralid. However, several treatments might be required to eradicate the weed, including its seed bank.
Lead Editor for Insight Weeds.