Tag Archives | weed profile

American Pokeweed (Phytolacca americana)

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Common names:

pokeweed, common pokeweed, inkberry, pigeonberry, pokeberry, poke

Scientific Name:

Phytolacca americana

Description:

Pokeweed is an herbaceous perennial in the Phytolaccaceae (pokeweed) family. It has creamy-white flowers that turn to dark purple hanging clusters of berries. The leaves are smooth and spade shaped, and the stems are often pinkish or red. It has a large, fleshy taproot that it re-sprouts from every spring. It spreads mostly by berries that are eaten by birds.

Life cycle:

Perennial

Height of mature plants

up to 10 feet tall, though usually closer to 4-6 feet tall.

Flower color:

Creamy white

Bloom time:

June – July

Look-a-likes:

Pokeweed looks a bit like knotweed species, although the clusters of purple berries are very distinctive of pokeweed

Habitat:

Pokeweed can often be found in yards, pastures, forest openings or disturbed sites, and often in areas like fence lines or underneath power lines (where birds like to rest).

Impacts:

While native to the southeastern United States, pokeweed is not native to Oregon and can form dense patches that crowd out native plants. The plant is also toxic to people, livestock, and pets (although properly prepared, it can be edible). It can spread into natural areas when birds eat the berries and carry the seeds to new places. It is also difficult to control as the taproot can grow very large, up to the size of a bowling ball.

Noxious Weed Listing:

Origin:

Southeastern United States

Links:

4-County CWMA invasive plant fact sheet
East Multnomah SWCD weed profile
City of Portland BES watch species profile
Invasive.org profile

 

Gorse (Ulex europaeus)

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Common names:

European gorse, common gorse, furze, whin

Scientific Name:

Ulex europaeus

Description:

Gorse is a stout, thorny evergreen shrub in the Fabaceae (pea) family. It has erect, spreading, angular branches that are covered in 1/2 – 2 inch spines. The flowers are yellow, fragrant and pea- shaped, and they form clusters at the end of the thorny branches. The seed pods are hairy, turn brown as they ripen, and then burst to scatter their seeds several feet away. It mostly spreads by seed, but there is also some vegetative spread. It was introduced to Bandon, Oregon in the 1890’s as a living fence.

Life cycle:

Perennial

Height of mature plants

Up to 10 feet tall

Flower color:

yellow

Bloom time:

March – May

Look-a-likes:

Gorse is sometimes compared to scotch broom or other broom species, though the thorns on gorse make it easily distinguished from these other plants that do not have thorns.

Habitat:

Gorse can be found in open, disturbed areas, as well as shady stream-sides and grasslands. It seems to do best in sandy or gravelly soils that have abundant moisture.

Impacts:

Gorse is considered to be one of the most difficult weeds to control in the world.It spreads rapidly, crowds out native plants, and its seeds stay viable in the soil for 30 years. It’s stout, thorny branches create dense stands that can impede wildlife movement and render land as nearly worthless. Furthermore, the spines contain oils, and when combined with the older dead branches, they create a serious wildfire hazard. the town of Bandon, Oregon (where gorse was first introduced to Oregon) was burned to the ground by a wildfire that was fueled by gorse infestations.

Noxious Weed Listing:

Origin:

Europe

Links:

Oregon Noxious Weed Profile
Washington Noxious Weed Profile
Invasive.org profile
CABI Invasive Species Compendium
Global Invasive Species Database

 

Sulphur Cinquefoil (Potentialla recta)

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Common names:

upright cinquefoil, rough-fruited cinquefoil, five-finger cinquefoil, yellow cinquefoil

Scientific Name:

Potentilla recta

Description:

Sulphur cinquefoil is an upright perennial in the Rosaseae (rose) family. The flowers are light yellow with five petals and a darker yellow center. The leaves have 5-7 leaflets and are rough and hairy with toothed margins. The stems are very hairy with quarter inch long hairs that stick out from the stem. It spreads through its abundant seed production.

Life cycle:

Perennial

Height of mature plants

Up to 3 feet tall

Flower color:

light yellow

Bloom time:

May – early July

Look-a-likes:

Sulphur cinquefoil looks very much like the native slender cinquefoil (Potentilla gracilis), and therefore care should be taken when identifying it. The main differences between these two are that the native slender cinquefoil has petals that are darker yellow, the leaves are a bit silvery on the underside, and the hairs are longer and perpendicular to the stem. Before flowering, the leaves are also sometimes mistaken for marijuana, though once the yellow flowers appear it is very easy to distinguish between the two.

Habitat:

Sulphur cinquefoil grows best in sunny, open habitats, so it is likely to grow in meadows, pastures, roadsides, railroads, logged areas, or abandoned lots.

Impacts:

Sulphur cinquefoil is a very aggressive noxious weed that displaces native forbs and grasses, and can even outcompete some other invasive plants. It can degrade the value of pastures and rangelands as it is unpalatable to livestock and wildlife. It is also drought tolerant and very adaptable. A single plant can live 20 years and can produce up to 5000 seeds.

Noxious Weed Listing:

Origin:

Asia and Europe

Links:

Oregon Noxious Weed Profile
Washington Noxious Weed Profile
King County Noxious Weed Profile
Invasive.org profile
Invasive Plant Atlas profile

 

Policeman’s Helmet (Impatiens glandulifera)

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Common names:

Policeman’s helmet, ornamental jewelhead, Himalayan balsam

Scientific Name:

Impatiens glandulifera

Description:

Policeman’s helmet is a showy, succulent annual in the Balsaminaceae (balsam) family. It was introduced as an ornamental plant, but it easily escapes cultivation and becomes invasive. The stems are hollow and succulent, with long leaves coming out at the nodes. The leaves have serrated margins and flowers that resemble old-fashioned English policeman’s helmets (thus, the name). A single plant can produce up to 800 seeds that are ejected up to 20 feet when ripe.

Life cycle:

Annual

Height of mature plants

Up to 8 feet

Flower color:

White to pink to purple

Bloom time:

June – August

Look-a-likes:

Policemen’s helmet looks very similar to other Impatiens species. However, the combination of the flower color (white, pink or purple vs the yellow-orange of other species), strongly serrated leaf edges, and the height make it fairly easy to distinguish.

Habitat:

Policeman’s helmet grows very well in moist natural areas, so it is often found along shady streams, ditches, and in moist forests.

Impacts:

Policeman’s helmet spreads rapidly, producing up to 800 seeds that can live a year and a half. They can form dense patches that exclude other native plants. Because they are annuals, they die in the summer, leaving behind bare soil which causes erosion and water quality problems.

Noxious Weed Listing:

Origin:

Asia (western Himalayas and India)

Links:

Oregon Noxious Weed Profile
Washington Noxious Weed Profile
Invasive.org Profile
CABI Invasive Species Compendium
Impatiens Identification Brochure

 

Purple Loosestrife (Lythrum salicaria)

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Common names:

Purple loosestrife, purple lythrum, spiked loosestrife

Scientific Name:

Lythrum salicaria

Description:

Purple loosestrife is an herbaceous wetland plant in the Lythraceae (loosestrife) family. It has showy, upright clusters of purple flowers. The stem is 4 to 6 sided, with leaves that are opposite and sometimes have smaller leaves coming out at the nodes. It was introduced through the ballast of ships in the 1800s and is also sometimes introduced through plant trades and sales.

Life cycle:

Perennial

Height of mature plants

Up to 10 feet tall (but usually closer to 3-5 feet tall)

Flower color:

pink to purple

Bloom time:

July to September

Look-a-likes:

Purple loosestrife can be confused with native spirea (Spirea douglasii) or native fireweed (Chamerion angustifolium). One of the obvious differences is the leaves; purple loosestrife leaves are arranged in an opposite pattern, while the look alikes have alternating leaves.

Habitat:

Purple loosestrife grows in wet areas such as wetlands, streamsides, and marshes.

Impacts:

Purple loosestrife grows vigorously in wet areas and can become dense, crowding out other vegetation. A mature plant can produce up to 2.5 million tiny seeds, which can spread by water and and birds. However, it can also reproduce by stem fragments. Areas that are heavily infested with this plant see a reduction in quality habitat for waterfowl and song birds.

Noxious Weed Listing:

Origin:

North Africa, Asia, Australia, and Europe

Links:

Oregon Noxious Weed Profile
Washington Noxious Weed Profile
Invasive.org profile
CABI Invasive Species Compendium
Global Invasive Species Database

 

Rush Skeletonweed (Chondrilla juncea)

Common names:

rush skeletonweed, naked weed, gum succory, hogbite, devil’s grass

Scientific Name:

Chondrilla juncea 

Description:

Rush skeletonweed is a perennial forb with many branched, wiry stems that range from 1-4 feet tall. They have few leaves when in bloom, and have coarse, red, downward-pointing hairs at the base of the flowering stem. In the spring, rosette leaves resemble common dandelion and are hairless with deep, irregular teeth that point back toward the leaf base. Leaves produce a milky white juice when torn. Rosettes generally wither by flowering time.  Small, yellow flower heads are a ½ inch in diameter and appear in early summer, growing in leaf axils and stem tips in singles or in clusters.  They have 7-15 yellow ray flowers and 2 rows of green flower bracts at the base of the flower head.  Seeds are 3mm long with a ribbed surface and white bristles on one end that aid in wind dispersal.

Life cycle:

Perennial

Height of mature plants

Up to 4 feet

Flower color:

Yellow to White

Bloom time:

April through May

Look-a-likes:

In the spring, rush skeletonweed rosette leaves resemble common dandelion and are hairless.  The flowers are also very similar to dandelion and dandelion-like plants.

Habitat:

Rush skeletonweed thrives in well-drained, sandy or gravelly soils and has invaded extensive areas of shallow silt loam soils.  It is found in pastures, rangeland, along roadsides, railways, and in open and disturbed areas.

Impacts:

Without control measures, this weed will produce a monoculture of interconnected plants. A single plant can become an entire colony.  Rangeland infestations displace native and beneficial forage grazed by livestock and wildlife.

Noxious Weed Listing:

Origin:

Europe and Asia

Links:

Oregon Noxious Weed Profile

Invasive.org profile

CABI Invasive Species Compendium 

Washington State Noxious Weed Control Beard

USDA Plants Database

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Primrose Willow and Water primrose (Ludwigia grandiflora, Ludwigia hexapetala, Ludwigia peploides ssp. montevidensis)

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Common names:

Large-flower primrose willow (L. grandiflora);

primrose willow, Uruguay primrose willow (L. hexapetala);

water primrose, creeping water primrose, hairy water primrose, floating primrose, floating primrose-willow (L. peploides ssp. montevidensis)

Scientific Names:

Ludwigia grandiflora

Ludwigia hexapetala

Ludwigia peploides ssp. montevidensis,

Description:

These three species in the Onagraceae (evening primrose) family, Ludwigia grandiflora, L. hexapetala, and L. peploides ssp. montevidensis are very similar and difficult to tell apart. All three species have bright yellow flowers with 5 petals that are about an inch wide. The reddish stems root freely at the nodes. The leaves are alternate, elongated, and willow-like, although they are more oval on young plants. They were introduced through the aquatic plant trade and spread through seeds, and root and stem fragments.

Life cycle:

Perennial

Height of mature plants

Large-flowered primrose willow (L. grandiflora) stems can be up to 10 feet long, while primrose willow (L. hexapetala) and water primrose (L. peploides) stems only grow up to 6 feet.

Flower color:

Yellow

Bloom time:

Late July – early September

Look-a-likes:

These plants can sometimes be confused with water purslane (Ludwigia palustris), which has small and inconspicuous green flowers and opposite leaves. They can also be confused with other yellow-flowered streamside plants such as the natives monkey flower and stream violet. However, upon closer examination, the flowers and leaves are quite different. To distinguish among these three non-native Ludwigia species a DNA test is often required.

Habitat:

Water primrose and the primrose willows are aquatic plants that grow in still or slow moving water such as wetlands, ditches, sloughs, ponds, and lake margins.

Impacts:

Ludwigia species forms dense mats that clog waterways, and this can interfere with water recreation, irrigation, fish passage, and flood control. When it clogs waterways, it also reduces the amount of oxygen in the water which can make it hard for other plants and animals to survive. As this species can out-compete other species, it can reduce the diversity of plants, and reduce the available habitat for birds and fish. It can spread and reproduce through leaf and stem fragments, as well as seeds, making control extremely difficult.

Noxious Weed Listing:

Origin:

South and Central America, and some parts of southern North America

Links:

Oregon Noxious Weed Profile- L. hexapetala and L. peploides
Washington Noxious Weed Profile- L. hexapetala
Washington Noxious Weed Profile- L. peploides
CABI Invasive Species Compendium-L. grandiflora
CABI Invasive Species Compendium-L. peploides

Goatsrue Eradication Project

Since 2016, the WeedWise program has been working to control the largest known infestation of goatsrue (Galega officinalis) in Oregon. Goatsrue is an Oregon class A noxious weed and has been deemed a high priority for control and eradication because it is toxic to livestock and spreads easily.  This federal and state noxious weed is only known at a handful of other sites across Oregon and the Pacific Northwest.

Goatsrue flowers

About Goatsrue

Goatsrue is a deep-rooted perennial, with hollow stems and compound alternate leaves.  The compound leaves have a terminal leaflet and 6-10 pairs of leaflets. The tip of each leaflet rapidly narrows to a fine tip. Goatsrue has pea-like flowers that vary in color from purple to white. Flowers bloom from June to October and are clustered at the end of its branches or at the leaf axils. Unlike some other members of the pea family, goatsrue lacks tendrils and grows in a more upright and bushy form rather than as a vine. The seeds are contained in pods with up to 9 mustard-colored, oblong seeds. Each plant can produce 15,000 pods a year. Additionally, these seeds may remain viable for 5-10 years in the soil.

Goatsrue closely resembles some regionally rare native plants, so we encourage landowners to contact us if they think they may have goatsrue on their property.

Robust goatsrue growth

What we Found

In May of 2016, during one of our planned weed surveys, one of our contracted survey crews discovered a large previously unknown population of goatsrue on two adjacent riparian properties along the Clackamas River. This infestation affects 14 acres and is the largest known infestation of goatsrue in Oregon. At that time, we began a management effort to contain and control this priority weed with the goal of eradication of the goatsrue as well as several other priority invasive plants present at these sites.

This discovery was found as part of extensive surveys of streamside properties along the Clackamas River initiated in 2015 and continuing into the present. Twenty-one priority invasive plant species were on our target list for these surveys. Some of these species had been documented in our region and some had not. These surveys help us to address new priority invasive plants and better manage priority invasive plants established here. We thank private landowners for allowing us to access their properties for these surveys!

Goatsrue herbicide application

What we are doing

The WeedWise Program initiated control soon after detection of this large infestation. Our approach began confirming the identity of the goatsrue. We then followed up with a thorough review of the biology and control of goatsrue. Most notably, we learned that goatsrue can have a long seed dormancy period allowing seeds to grow after 10 years in the soil. As a perennial weed with a deep taproot, it is all difficult to remove by hand. Therefore, our management goals were to prevent all seed production and to target the large root systems of existing plants.

Next, we researched management strategies appropriate for this plant and this site. We also consulted with the Oregon Department of Agriculture Noxious Weed Control Program and the City of Portland Bureau of Environmental Services who both have prior experience managing goatsrue. Based on this research, we selected two herbicides to treat the infestation: one to target upland populations and a second aquatically approved herbicide to treat infestations that occur near water. The herbicide applications were planned by the WeedWise program and implemented using licensed restoration contractors.

What’s Next?

To date, our management efforts have been highly successful, but with the size and complexity of the site we did note some patches with regrowth after herbicide application, as well as new seedlings emerging. On follow-up monitoring of the site, we also found several overlooked patches that had grown in an among other vegetation. In response, our current efforts focus on continuing to scout for missed populations and to remove interspersed invasive Himalayan blackberry (Rubus bifrons) stands which may obscure goatsrue plants. We are carrying out multiple rounds of control each year to ensure that we are not letting any plants go to seed and to continue to address regrowth.

After two years of intensive control, we have dramatically reduced the populations and are on track to eradicate this population. Eradication will require ongoing monitoring and control to address the long seed dormancy. Although we won’t be walking away from the site anytime soon, we are optimistic knowing that the population is significantly reduced, and that we are committed to eradicating goatsrue from Clackamas County!

Project Photo Gallery

Meadow Hawkweed (Hieracium caespitosum)

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Common names:

Meadow hawkweed, yellow hawkweed, field hawkweed, yellow paintbrush, devil’s paintbrush, yellow devil, yellow fox-and-cubs

Scientific Name:

Hieracium caespitosum (synonym: Hieracium pratense)

Description:

Meadow hawkweed is a perennial in the Asteraceae (sunflower) family. The stem and leaves contain a milky juice. Flower heads are yellow, dandelion-like, and grow in clusters of 5 – 30 at the top of the stems. Each plant can produce 10 – 30 flowering stems. The bracts below the flowerheads are covered in black hairs. The clustered buds are rounded and also covered in black hairs. The leaves are mostly at the base of the plant and are hairy with edges that are either smooth or very minutely toothed. It can spread by seed, rhizome, or stolon.

Life cycle:

Perennial

Height of mature plants

Up to 3 feet

Flower color:

Yellow

Bloom time:

May – July

Look-a-likes:

At first glance, meadow hawkweed looks like a common dandelion (Taraxacum officinale) or even a false dandelion (Hypochaeris radicata). However, on meadow hawkweed, the flower heads are more clustered, the buds and stems are covered with black hairs, and the leaves are not lobed like the dandelion and false dandelion. Identification between meadow hawkweed and some of the other hawkweeds can be extremenly difficult, although the above-ground stems and virtual lack of leaves on the stem (occasionally 1-2 small leaves) are helpful characteristics to narrow down the options.

Habitat:

Meadow hawkweed prefers sunny areas, although it can be somewhat shade tolerant. It grows well in low fertility soils and is well-adapted to higher elevations. You can find this plant in meadows, woodlands, fields, and disturbed sites like roadsides, pastures, and gravel pits.

Impacts:

Meadow hawkweed is an aggressively invasive plant that spreads easily and can form monocultures. It out-competes other plants for water, nutrients, and physical space. Its decaying leaves contain chemical compounds that can harm other plants.

Noxious Weed Listing:

Origin:

Europe

Links:

Oregon Noxious Weed Profile
Washington Noxious Weed Profile
Invasive.org profile
King County Noxious Weed Profile
CABI Invasive Species Compendium

Flowering Rush (Butomus umbellatus)

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Common names:

Flowering rush, grass rush, water gladiolus

Scientific Name:

Butomus umbellatus

Description:

Flowering rush is an aquatic perennial plant in the Butomaceae family. Leaves are thin, and either straight or slightly twisted, up to 40 inches long, and have a triangular cross-section at the base. When the plant is submerged the leaves are flexible, and when emerging along the shoreline, they are more stiff. Flowers have 3 large pink petals (with three sepals below that look like petals), and grow in flat-topped clusters of 20-50 on tall cylindrical stalks. It has fleshy rhizomes that trail along the ground (??). It was introduced as an ornamental and is sometimes still sold for water gardens. It spreads mostly through rhizome fragments or small bulbils that detach and disperse through the water, though some varieties also produce seeds.

Life cycle:

Perennial

Height of mature plants

Up to 5 feet

Flower color:

Light pink

Bloom time:

June – August

Look-a-likes:

While not a true rush, it looks similar to many other rushes and bulrushes

Habitat:

Flowering rush requires wet soil and sunshine. It can be found in wetlands, irrigation ditches, shorelines, and along slow-moving streams and rivers, and it can grow in water up to 9 feet deep. It often grows in areas with fluctuating water levels and can tolerate a wide variety of temperatures.

Impacts:

Flowering rush is an aggressive colonizer that can out-compete native wetland and shoreline vegetation. It can clog slow moving waterways and impede boat travel and fishing along shoreline, thus degrading both their recreational and ecological value. As an aquatic plants that spreads vegetatively, it is difficult to control, and can be easily spread by waterfowl, wildlife, and boaters.

Noxious Weed Listing:

Origin:

Northern Africa, Asia, and Europe

Links:

Oregon Noxious Weed Profile
Washington Noxious Weed Profile
King County Noxious Weed Profile
Invasive.org profile

 

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