Contact Info
Missouri River Institute
The University of
South Dakota
414 E. Clark Street
Science Center
Vermillion, SD 57069

Financial support for website development provided by the
Living River Group
of the
Sierra Club




Poison Ivy (Toxicodendron radicans)

Poison ivy is a woody vine with compound leaves comprised of three leaflets.  The margins (edges) of the leaves may be smooth, toothed, or lobed.  Poison ivy produces clusters of small green flowers in June and July.  The fruits are small, white berries.  Many bird species use the seeds as a food source, and thus spread seeds to new areas.  Poison ivy grows in a variety of habitats, but is most commonly found on the edges of wooded areas.  Plants may occur as erect shrubs or as vines climbing trees, fences, or buildings, and can often turn bright red and yellow in the fall.  Virginia creeper has a similar growth habit and frequents the same habitats as poison ivy, but is easily distinguished from poison ivy because it has five leaflets instead of three.  Poison ivy is responsible for more than 2 million cases of skin poisoning each year.  The toxin causes inflammation and swelling, accompanied by painful irritation and blisters.  Symptoms usually occur within 12 to 24 hours after contact with the plant, but sometimes may not appear until 3 to 4 days after exposure.  The toxin is an oily compound present in all parts of the plant.  The toxin retains its potency even after plants have been killed.  The oil can be carried on clothing, tools, pets, and in smoke, and it retains its toxicity for long periods.  Poison ivy is commonly found along the riparian forests and islands along the Missouri River, and should be avoided whenever possible.  Remember the old saying… "Leaves of three, let it be"

Sweet Clover (Melilotus albus)

Sweet clover is a biennial herb that is very common in the riparian habitats along the Missouri River.  Native to Europe and Asia, sweet clover was originally introduced to North America in the early 1900's to serve as a supplemental forage crop, and can now be found in all 50 U.S. states.  Plants can grow to approximately 7 feet in height, and can sometimes be woody at the base.  Flowering occurs from April to September, when yellow, pea-like flowers develop in a branched inflorescence at the tips of the flowering stems.  Individual flowers are less than ¼ inch long, and fruits are small, circular, and light brown pods that contain 1 seed.  These seeds may remain viable in the soil for years (up to 30 years or more).    Sweet clover has adapted to a variety of conditions, withstanding both hot and cold climates.  Plants occur along roadsides, in open fields, pastures and other disturbed areas.  It grows well in direct sunlight and in partial shade.  Sweet clover is an obligate biennial, which means that the plant always puts its energy into developing a healthy root system during the first season, and during the second season, it flowers, sets seed and dies. 

Purple Loostrife (Lythrum salicaria)

Purple loosestrife is an invasive and non-native perennial herb found along the Missouri River that grows to a height of 3-10 feet.  Originally from Eurasia, mature plants can have 1 to 50 4-sided stems that are green to purple and often branched, making the plant bushy and woody in appearance.  The flowers are magenta-colored with five to seven petals and bloom from June to September.  Seeds are contained in capsules that burst at maturity in late July or August, and are dispersed by wind and water.  A single stem can produce an estimated two to three million seeds per year from a single rootstock.  Purple loosestrife is capable of invading wetlands such as wet-meadows, river and stream banks, pond edges, backwater edges, and ditches.  Once established, patches of purple loosestrife can expand and grow very quickly, often out competing native grasses, sedges, and other native flowering plants.  Once established, control of purple loosestrife is very difficult and expensive.  Physical removal and the utilization of herbicides are the most typical control methods used.

Canada Thistle (Cirsium arvense)

Canada thistle is a non-native, and invasive species commonly found in the riparian habitats along the Missouri River.  It is an herbaceous perennial that grows to 1.5-4 feet tall, and has prickly leaves and an extensive creeping root-system.  The stems are branched, often slightly hairy, and ridged.  Leaves are simple, lance-shaped and irregularly lobed with spiny, toothed margins, and are arranged alternately along the stem.  Fragrant, rose to purple, and sometimes white flower heads appear from June through October.  Small light brown seeds break off easily, fall near the parent plant, and are wind dispersed.  One plant is capable of producing up to 5,000 seeds, which are capable of germinating eight to ten days after they are dispersed.  Canada thistles have a very strong and fibrous tap root, that may easily extend feet into the soil.  It grows in barrens, glades, meadows, prairies, fields, pastures, and waste places.  It does best in disturbed upland areas but also invades wet areas with fluctuating water levels such as stream bank sedge meadows and wet prairies.  Natural communities that are threatened by Canada thistle include non-forested plant communities such as prairies, savannas, glades, sand dunes, field and meadows that have been impacted by disturbance.  This highly invasive thistle prevents the coexistence of other plant species through shading, competition for soil resources and possibly through the release of chemical toxins poisonous to other plants.  Repeated manual and chemical control efforts are necessary to control Canada thistle, however these methods can be quite expensive and only successful on a small scale.

Partridge Pea (Chamaecrista fasciculata)

The partridge pea is a native, annual plant commonly found along the Missouri River, and can grow to two feet in height.  Shorter plants are often erect, while taller plants are inclined to sprawl.  The slender hairless stems are initially light green, but become reddish brown in the fall.  The leaves are alternate and compound, and range in color from light to dark green.  Bright, irregularly shaped yellow flowers appear along the major stems from mid-summer through early Fall and are about 1" across. These flowers have no floral scent, however they are regarded as an important pollen source for honeybees and bumblebees.  The seeds of this plant are an important food item to many wildlife species, including greater prairie-chickens, ring-necked pheasant, waterfowl, grassland birds, and field mice.  Partridge pea grows on prairies, bluffs, riverbanks and river bottoms, as well as in upland hardwood forests.  Partridge pea is most common on sandy soils, and grows best in full sunlight, but can tolerate partially shady conditions.  Partridge pea has low water requirements, and can grow and produce seeds under extreme drought conditions.

Horsetail (Equisetum hyemale)

Horsetail is a very common plant often found in the riparian habitats along the Missouri River.  Also known as "Scouring Rush", it is a non-flowering, rush like evergreen perennial that typically grows 3-5' tall and is native to portions of Eurasia, Canada, and the U.S.  It typically occurs in wet woods, moist hillsides, and along bodies of water such as lakes, rivers, and ponds.  Horsetail has rigid, rough, hollow, vertically-ridged and segmented dark green stems that are up to ½" diameter at the base of the plant.  Each node (joint on the plant) has a tiny whorl of scale-like leaves that are fused into an ash gray sheath.  Photosynthesis is carried out in the stems of the plant, and some stems bear a pine cone-like fruiting head that contain numerous spores for reproduction.  The evergreen stems are particularly noticeable in the winter and can provide significant interest to the landscape.  Stems have a very high silica content and were used by early American settlers for polishing pots and pans, hence the common name scouring rush.