Crooked River Weed Management Area

Central Oregon

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A-Listed Species ... Crooked River Weed Management Area

African Rue

Peganum harmala
African rue is a bright green succulent, perennial herb, growing from a woody base. It normally will not grow over 1 foot tall. Its roots are deep, reaching depths of 20 feet in extremely dry soils.It has succulent, narrow, alternate leaves arranged on a stiff stem. The flowers are white,borne singly on the leaf axils of the stem, with five petals and are present from April to September.Seed pods will develop from May to October.Seeds are produced in a 3 chambered capsule,with many small seeds in each chamber.
Because of African rue’s elaborate root system,efforts to eliminate the plant by means other than herbicidal control are very difficult. The plant quickly grows back after mowing or burning, and deep cultivation only divides and spreads the roots. Numerous herbicides have been tested on African rue, but only chemicals that are moved deep into the plant’s root system have shown to be effective. Foliar active herbicides must be applied when the plant is actively growing to maximize chemical uptake and movement through all portions of the plant. Soil herbicides are applied to the surface and must move with the wetting front after rain.
African rue contains at least four alkaloids which are poisonous to sheep, cattle, horses and humans. The B-carboline alkaloid causes incoordination and paralysis. The seeds and fruit of the plant are the most toxic. A dose of 0.15% of the animal’s body weight is LETHAL. Young leaves are somewhat less toxic than seeds, with a lethal dose of 1% of the animal’s body weight. Dry leaves are not apparently toxic. Signs of chronic poisoning include; loss of appetite, listlessness,weakness of the hind legs, knuckling of the fetlock joints, stiffness, trembling, incoordination and frequent urination. When burned, the wood creates toxic smoke.
Dalmation Toadflax
Linaria dalmatica
Dalmatian toadflax is a perennial, growing up to 3 feet tall. It reproduces by seed and underground rootstocks. The plant contains from 1 to 25 vertical, floral stems. Flowers are bright yellow and resemble snapdragons. It has alternate, heart shaped, waxy leaves. The base of the leaves tend to wrap around the stem. It’s extensive deep tap root and waxy leaves make it hard to control
Where to find Dalmatian toadflax:

Dry open areas of rangelands, south and southeast facing slopes, roadsides, areas around dwellings, vacant lots, and other disturbed sites.
Mowing and burning are not recommended for toadflax because roots buds and seeds will remain unaffected. Grazing can be used if the timing is right. Overgrazing in the spring can increase establishment of toadflax by reducing competitive desirable plants. Herbicides can and have been effective for control. After initial weed control, areas should be seeded with a mixture of competitive, well-adapted species that include deep-rooted species. Bio-control agents have been effective as well. Pulling small populations in sandy or loose soil can be successful because there is a better chance of removing the entire rootstocks. 
Jointed Goatgrass
Aegilops cylindrica
Jointed goatgrass is a winter annual which means that it germinates in the fall and establishes a root system. The next spring it will grow, flower and set seed. Leaves are grass like, up to a ½ inch wide. Stems can grow up to 4 feet tall and are tipped with slender, cylindrical spikes that appear to be a series of joints stacked on top of each other. Reddish to straw-colored spikes emerge in May to June, and the uppermost joints are tipped by straight awns. Jointed goatgrass can be mistaken for winter wheat except that seedlings have evenly spaced hairs lining the leaf blade margin. These hairs usually are not present in winter wheat. If hairs appear on winter wheat
leaves, they’re longer and randomly spaced.

Be sure that harvesting equipment is free of jointed goatgrass seeds. Also, purchase weed free seed mixes and plant at the latest recommended date to give the jointed goatgrass less of a chance to establish. Keep open, disturbed areas such a roadsides and fence lines free of jointed goatgrass.

Non selective herbicides work well on jointed goatgrass. Seed may remain viable in the soil for several years. It is imperative that you keep jointed goatgrass out of crops. This can be done by keeping fence lines, ditches and right of ways clean, by treating them with herbicides.
Leafy Spurge
Euphorbia esula

Leafy spurge is an upright, branching, perennial herb two-three feet tall. It has alternate narrow leaves, somewhat frosted and slightly wavy along the margins. The flowers of this weed are very small and are borne in greenish-yellow structures surrounded by yellow distinctive heartshaped bracts.

Because of its aggressive nature, stopping the spread of seeds and vegetative buds is the most important. Clean yourself and equipment. Quarantine contaminated livestock (until seed is passed) and contaminated feeds.
Where to find Leafy spurge:

It is capable of invading disturbed sites, including stream banks, pastures, abandoned fields and roadside areas.

Biological control such as grazing or insects can be used to weaken populations,
but timing is key for grazing. Sheep and goats will graze leafy spurge in the spring and summer and grasses in the fall. Insects can be effective for control and can be purchased. Burning and pulling are ineffective for control and burning should only be used prior to herbicide applications. Chemical control should be used on small patches before further spread.
Mediterranean Sage
Salvia aethiopis

Mediterranean sage has erect, sturdy, squarish stems up to 3 feet tall, with opposite leaves and a stout taproot. The leaf area is densely woolly with white hairs, especially when young. As plants age, the upper sides of the leaves lose some of the felty covering of hairs, revealing prominent veins and a wrinkled surface. The pre-reproductive plant forms a ground hugging rosette. The rosette leaves are indented or shallowly toothed and have a stalk 1.5 to 3.5 inches long. At this stage Mediterranean sage can be confused with
common mullein. However, mullein leaves tend toward yellow-green, in contrast to the gray or blue-green cast of the Mediterranean sage leaves. Also, mullein leaves are not toothed along the margin and Mediterranean sage emits a pungent, sage like odor when crushed. Mature plants have upright stems with clasping leaves that become progressively smaller up the stem. The uppermost leaves are merely bracts, purple-tinged and tapering to long points. The branched panicle resembles a candelabra and bears numerous flowers in woolly clusters. The whitish flowers are in whorled clusters of 4 to 6, each encircled by silvery-varied bracts with pointed tips. Each flower is about ½ inch long, with the upper lip resembling a hooked beak and the lower yellow lip divided into 3 lobes.

Mediterranean sage is a wind-tumbled plant; therefore,stopping the plant from going to seed is important. Management of Mediterranean sage takes persistence and years of control to deplete the seed reserves. Manual treatments such as digging and mowing can be used on small or outlying populations. Be sure to dig up 2 to 3 inches of taproot or mow repeatedly throughout the growing season. Herbicides can be very successful, especially when applied with a superior surfactant during the rosette stage. Biological control has been successful in Oregon and Idaho in some instances. Unfortunately, ants tend to feed on the rootfeeding weevil that attacks the plant.
Musk Thistle
Carduus nutans

Leaves become more deeply lobed with age and each lobe has 3 to 5 points tipped with a spine. The plant develops a large, fleshy, corky taproot that is hollow near the soil surface. In the second year, musk thistle bolts and the shoots grow 2 to 6 feet tall. The leaves on the shoots are 3 to 6 inches long, alternate, clasped down the shoot and are deeply lobed. Shoots have spiny wings except a few inches below each flower head. Flower heads are solitary and terminal on shoots and bend about 90 degrees. They are about 1.5 to 3
inches in diameter, bright purple or rarely white. Flowers are subtended by numerous spine-tipped, green to brown bracts that resemble a pine cone. Musk thistle is most often mistaken for bull thistle. A major difference between these plants is that the
underside of bull thistle leaves are woolly.

Both musk and Scotch thistle reproduce solely from seed, therefore, the key is to stop seedproduction. The best long term control combines an integrated management system including; cultural, chemical and mechanical. Digging or cutting the plant below the soil surface can be very effective, but perennial grasses should be planted in these areas to create competition. Herbicide can be used on rosettes in the fall as well as rosettes and shoots in the spring.
Perennial Pepperweed
Lepidium latifolium

Perennial pepperweed is a long lived perennial which thrives in seasonally wet areas that have a high water table. It reproduces from perennial roots or seed. In early spring, new shoots emerge from root buds forming low growing rosettes. Plants are multiple stemmed and grow in stiffly erect masses up to 5 feet tall. The roots form a woody crown and are creeping forming new plants from root sections as small as two inches. Basal leaves are up to 1 foot long and 3 inches wide, while stem leaves are smaller, 3 to 10 inches in length and tapered at the base, entire to weakly serrate. Abundant small white 4-petaled flowers are borne in dense clusters near the stem tips. The fruits are small, flattened
pods, each containing two seeds. These pods will irregularly drop throughout the winter.

Perennial pepperweed has been used as an ornamental in landscapes so it’s important to not use it in landscaping. If found in your home landscape pulling can be done taking care to remove as much of the root as possible and treating with herbicide.

Perennial pepperweed rarely produces seedlings, reproducing mainly through the vegetative roots. Therefore, seed viability is not an issue. Short of drowning out control of this plant is difficult and takes a myriad of techniques. Spring grazing or mowing followed by an application of herbicide at the flower bud stage can be effective. If populations are small herbicide alone at the bud stage are also effective. In wetland areas mowing may be used followed by the appropriate herbicide. Mechanical treatment alone is not recommended due to its ability to resprout from the crown or small root sections.
Purple Loosetrife
Lythrum salicaria

Purple loosestrife is an erect semi-aquatic perennial herb. It has a square, woody stem and opposite or whorled leaves. The leaves themselves are lance shaped, stalkless, and heart-shaped or rounded at the base. Plants grow from 4 to 10 feet high. Flowers have 5 to 7 petals, bloom in a spike and are a brilliant magenta color. Flower petals also have a crushed appearance. Mature plants can have from 30 to 50 stems arising from a single rootstalk and dominating the herbaceous canopy. 
What to look for

Magenta flowers on stalks in moist or marshy areas
When to find purple loosestrife

From July to September when in bloom

The best control for purple loosestrife is time intensive and costly, which is why early detection is key to this species. Try cutting before flowering to reduce seed load, pulling or digging smaller populations ensuring to get as much of the root system as possible, or if feasible drowning the plant. Keep an eye on outgoing ditches or other waterways to make sure that they don’t also become infested. Pull new satellite infestations early before they become established. On large infestations spot treatment with chemicals, such as glyphosate that are safe to use near water can be effective. If populations become too large to manage biocontrols have been proven to control purple loosestrife.
Rush Skeleton Weed
Chondrille juncea

Rush skeletonweed is a perennial plant that grows from one to four feet tall. Juvenile plants overwinter as a rosette of hairless, basal leaves that are two to five inches long and widen towards the tip. Lateral lobes on the leaves of the basal rosette point backwards toward
the base. At maturity the plant becomes dark green, nearly leafless, and bears many branches. A distinguishing characteristic are its coarse downwardlybent hairs that cover the lower four to six inches of the stem. When cut, the stems and roots exude a white latex sap. Yellow flower heads that are ¾ inch in diameter grow along the stem in the leaf axils or at the branch tips. Flower heads may grow individually or in clusters of two to five. Seeds have a pappus of numerous white capillary bristles that are carried by the wind.
            - Thin aerial branches with few-to-no leaves
            - Lateral lobes on basal rosette leaves, pointing back toward the base
            - Downwardly bent hairs on the stem between the rosette and the first whorl of leaves.

It’s important to catch and control this plant before it flowers and sets seed (July –September) so as to prevent its dandelion-like seeds from being widely dispersed. Therefore, look for this plant during late fall and winter when it appears as a basal rosette.

Pulling or tilling rush skeletonweed is not recommended due to its creeping nature. Fall treatment using Tordon 22K can be very effective using a GPS to go back to previously identified sites. Spot spraying with glyphosate is also a common practice. This should be done with care to keep from injuring nearby plants.
Scotch Thistle
Onopordum acanthium

Leaves are large, green, and spiny, covered with fine dense hairs on both sides, giving a grayish green, cottony appearance. Leaves on the rosette may be as much as 2 feet long and have a distinct white midrib. Leaves of young plants are oblong while leaves of older plants are more rectangular. Scotch thistle has a fleshly taproot. Flowering
shoots grow 8 feet or more. They are very hairy or cottony and have a distinct winged appearance. Prominent triangular lobes occur on the leave margins. These lobes end in a sharp, green to white spine. Flowers are numerous, 1 to 2 inches in diameter, pale purple to red and flat on top. Flowers are subtended by a series of overlapping bracts, each tipped with a spine.

Both musk and Scotch thistle reproduce solely from seed, therefore, the key is to stop seed production. The best long term control combines an integrated management system including; cultural, chemical and mechanical. Digging or cutting the plant below the soil surface can be very effective, but perennial grasses should be planted in these areas to create competition. Herbicide can be used on rosettes in the fall as well as rosettes and shoots in the spring.
Tansy ragwort 
Senecio jacobaea
Tansy ragwort can be identified in its first year basal rosette stage, or in its mature second year flowering stage. Basal leaves can be hairless to lightly covered with whitish cottony hairs, especially on leaf undersides. The basal rosette has a ruffled appearance, due to its deeply indented and blunt-toothed lobing of the leaves. Mature plants are one to four feet tall, with stem leaves alternate on the stem and sessile. Flower inflorescences are in flat topped clusters, with each 20-60 flower heads per plant. Each flower head is composed of yellow, daisy-like flowers. Tansy ragwort has a taproot, and often a large woody rootstock.
            -Leaves dark green on top, whitish-green underneath, with a ragged, ruffled appearance.
            -Mature plants generally 1 to 4 feet tall
            -12-15 yellow ‘petals’, which are ray flowers
            - Flower heads in clusters of 20-60
Flowers June to October; seeds in August
            Look for tansy is sunny disturbed areas, such as roadsides and heavily-grazed pastures
Dig up the whole plant including roots. Flowers will go to seed after pulling, so bag and discard flower stalks.
Wild Carrot
Daucus carota
Wild carrot, or Queen Anne’s lace, is biennial. During the first year it develops a lacy rosette. The hollow flower stalk develops in the second year and stands between 2 and 4 feet in height. The flowers are small and white with the center flower usually being purple.
The flowers together form an umbel or the umbrella shape shown above, 3 to 6 inches in
What to look for:

Umbrella-like flower head made up of
small white flowers
When & where to find wild carrot:

Look in midsummer when wild carrot is in

Because wild carrot is a biennial, stoppingseed production is a good form of control.
This can range from cultivation, mowing, pulling or chemical control. Wild carrot may
be controlled by herbicides at three stages of growth: overwintered plants with early preplant, pre-emergence or post-emergence herbicide applications; established plants with
fall herbicide applications; and seedlings with pre-emergence or post-emergence herbicide
applications. Overwintered and established plants are generally more difficult to control
than seedlings.
Yellow Starthistle
Centaurea solstitialis
Yellow starthistle grows to a height of 2 to 5 feet. The plant stem is erect and rigid, bears many branches and is covered with white cottony hair. Its foliage is grey to bluish-green, and its leaves nearest to the soil are deeply lobed, while its upper stem leaves are almost linear or narrowly oblong. The leaf bases extend down the stems giving the stem a winged appearance. It generally flowers May through December, but in Oregon, it flowers July through September. The flower heads are yellow, located singly at theends of branches, and are armed with thorns up to ¾ inch long.
            • Yellow flower heads and long, sharp spines
            • Leaf bases extend down the stems giving it a winged appearance

Yellow starthistle is most easily found when flowering from July through September. It grows in dry areas, rangelands, pastures, edges of cropland, open woodlands, roadsides and disturbed areas. It favors sites originally dominated by perennial bunchgrasses such as south slopes with 12-25 inches of annual rainfall.

Small populations can be hand pulled. Effective control of yellow starthistle requires the suppression of seed production and an integrated approach using multiple control
methods such as mechanical and chemical. Mowing below branches and prior to seed
formation can help reduce populations. After control, establishment of perennial grass cover is usually necessary.

Eurasian watermilfoil
Myriophyllum spicatum



Eurasian water-milfoil is a non-native rooted aquatic plant with long stems that branch near the water's surface to create a canopy of floating foliage. The leaves are in whorls of four with 14-20 pairs of feathery leaf divisions. A spike of pink flowers emerges above the water and then falls horizontally when in fruit. Eurasian water-milfoil closely resembles the native northern water-milfoil (M. exalbescens). A reliable distinguishing characteristic is the number of leaf divisions; northern water-milfoil has fewer (5-12) than the non-native species.


Submerged green leaves that become limp when removed from water.  They are usually arranged in whorls of four around each node of the stem.  Each leaflet has 14-24 hairlike, paired divisions.  The flower spike extends with redish flowers up to  8 inches above the water surface.  Stems are brownish-red to light green in color.


Eurasian water-milfoil can grow in a variety of aquatic habitats, but prefers fertile, fine-textured inorganic sediments. It is an opportunistic species that invades disturbed lake beds, recreational waterways and slow moving streams. Optimal growth occurs in alkaline systems with high concentrations of dissolved inorganic carbon.


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