''Amaranthus tuberculatus'', commonly known as roughfruit amaranth, rough-fruited water-hemp, tall waterhemp, or common waterhemp, is a species of

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

. It is a summer annual broadleaf with a germination period that lasts several months. Tall waterhemp has been reported as a

weed A weed is a plant considered undesirable in a particular situation, "a plant in the wrong place", or a plant growing where it is not wanted.Harlan, J. R., & deWet, J. M. (1965). Some thoughts about weeds. ''Economic botany'', ''19''(1), 16-24. ...

in 40 of 50

U.S. states In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sove ...

Morphology

A distinguishing characteristic of tall waterhemp that sets it apart from similar members of the genus

Amaranthus ''Amaranthus'' is a cosmopolitan genus of annual or short-lived perennial plants collectively known as amaranths. Some amaranth species are cultivated as leaf vegetables, pseudocereals, and ornamental plants. Catkin-like cymes of densely pac ...

is the lack of hair on its stems and

leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...

. This characteristic gives the plant a bright, glossy appearance. The leaves of tall waterhemp tend to be long and narrow. The stem is typically erect and slender and can be up to three feet long. The color of the stem is green or red. Tall waterhemp is a

dioecious Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproductio ...

plant. The seedhead branches in the female are numerous, short, and smooth. The male seedhead branches are fewer, longer, and more slender than those of the female. The species has terminal spike

inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...

s and very short

bract In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or of ...

s with simple to highly branched flowers. Seed produced is reddish to black and less than 1/32 inch in diameter.

Geographic distribution

Tall waterhemp is native to

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

. It is believed to have originally had a range north of

Missouri Missouri is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. Ranking List of U.S. states and territories by area, 21st in land area, it is bordered by eight states (tied for the most with Tennessee ...

and

Tennessee Tennessee ( , ), officially the State of Tennessee, is a landlocked state in the Southeastern region of the United States. Tennessee is the 36th-largest by area and the 15th-most populous of the 50 states. It is bordered by Kentucky to th ...

to the

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five lakes ...

. It is now found in 40 states but is most common in the

Great Plains The Great Plains (french: Grandes Plaines), sometimes simply "the Plains", is a broad expanse of flatland in North America. It is located west of the Mississippi River and east of the Rocky Mountains, much of it covered in prairie, steppe, an ...

and

regions.

Habitat

Tall waterhemp predominantly grows in wet habitats, such as ponds, marshes, lakes, creeks, and other

riparian A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the terrestrial biomes of the Earth. Plant habitats and communities along the river margins and banks ar ...

zones. It also thrives along roadways and railroads as well as agricultural fields. It can grow in a variety of climates, as evidenced by its widespread range.

Growth and development

Tall waterhemp is a summer annual that produces a large number of very small seeds. It is considered an

r-strategist In ecology, ''r''/''K'' selection theory relates to the selection of combinations of traits in an organism that trade off between quantity and quality of offspring. The focus on either an increased quantity of offspring at the expense of individ ...

Emergence In philosophy, systems theory, science, and art, emergence occurs when an entity is observed to have properties its parts do not have on their own, properties or behaviors that emerge only when the parts interact in a wider whole. Emergence ...

can span several months and often occurs later in the season than other annual weeds, allowing the weed to evade typical weed control strategies such as

herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...

application and

tillage Tillage is the agricultural preparation of soil by mechanical agitation of various types, such as digging, stirring, and overturning. Examples of human-powered tilling methods using hand tools include shoveling, picking, mattock work, hoein ...

. One study observed 80% emergence not occurring until ten weeks after the initial emergence. Extreme temperatures have little effect on seed viability.

Germination Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, fer ...

occurs typically after soil temperature alternation, as this is required to break seed dormancy. Waterhemp has been found to germinate in a wide range of soil and temperature conditions. It has been found to germinate 17 years after seed set. While tall waterhemp cannot

self-pollinate Self-pollination is a form of pollination in which pollen from the same plant arrives at the stigma of a flower (in flowering plants) or at the ovule (in gymnosperms). There are two types of self-pollination: in autogamy, pollen is transferred t ...

, due to having separate male and female plants, it does not require any vectors for pollination. This allows for wind pollination over large distances, generating a large amount of

genetic diversity Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species, it ranges widely from the number of species to differences within species and can be attributed to the span of survival for a species. It is dis ...

. Another factor contributing to

is the large amount of seed produced. Tall waterhemp in competition with

soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses. Traditional unfermented food uses of soybeans include soy milk, from which tofu an ...

has been reported to produce from between 300,000 and 5,000,000 seeds per plant.Hartzler, R.G., B.A. Battles and D. Refsell. 2004. Effect of common waterhemp emergence date on growth and fecundity in ''Glycine max''. Weed Sci. 52. Tall waterhemp also has a rapid growth rate, 50–70% greater than other annual weeds.

Interspecific hybridization

Interspecific hybrids of tall waterhemp and ''

Amaranthus hybridus ''Amaranthus hybridus'', commonly called green amaranth, slim amaranth, smooth amaranth, smooth pigweed, or red amaranth, is a species of annual flowering plant. It is a weedy species found now over much of North America and introduced into Europ ...

'' have been observed in experimental fields but have not been observed in agronomic fields.

Agricultural impacts and control

, tall waterhemp is considered a major weed of agricultural fields and other disturbed habitats. The

Southern Weed Science Society Southern may refer to: Businesses * China Southern Airlines, airline based in Guangzhou, China * Southern Airways, defunct US airline * Southern Air, air cargo transportation company based in Norwalk, Connecticut, US * Southern Airways Express, M ...

includes tall waterhemp on their list of weed species. However, it is not listed on the federal

noxious weed A noxious weed, harmful weed or injurious weed is a weed that has been designated by an agricultural or other governing authority as a plant that is injurious to agricultural or horticultural crops, natural habitats or ecosystems, or humans or liv ...

list or any state lists in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

. In

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

and other continents where the species has been introduced, naturalization is an infrequent occurrence. Because of the long germination window for tall waterhemp, a single herbicide application is unlikely to be an effective control strategy.

Michigan State University Michigan State University (Michigan State, MSU) is a public university, public Land-grant university, land-grant research university in East Lansing, Michigan. It was founded in 1855 as the Agricultural College of the State of Michigan, the fi ...

Extension recommends a preemergence application followed by one or more postemergence applications. Some populations of tall waterhemp have been reported resistant to

acetolactate synthase The acetolactate synthase (ALS) enzyme (also known as acetohydroxy acid or acetohydroxyacid synthase, abbr. AHAS) is a protein found in plants and micro-organisms. ALS catalyzes the first step in the synthesis of the branched-chain amino acids ...

inhibiting (ALS)

herbicides Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...

and the

triazines Triazines are a class of nitrogen-containing heterocycles. The parent molecules' molecular formula is . They exist in three isomeric forms, 1,3,5-triazines being common. Structure The triazines have planar six-membered benzene-like ring but ...

, with some individual weeds being resistant to both

groups. Resistance to

acifluorfen Acifluorfen is the ISO common name for an organic compound used as an herbicide. It acts by inhibiting the enzyme protoporphyrinogen oxidase which is necessary for chlorophyll synthesis. Soybeans naturally have a high tolerance to acifluorfen ...

and other diphenyl ether herbicides has been reported. Even more alarming is the emergence of waterhemp resistant to the latest generation of herbicides, HPPD inhibitors. Furthermore, waterhemp at a site in

Nebraska Nebraska () is a state in the Midwestern region of the United States. It is bordered by South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Kansas to the south; Colorado to the southwe ...

was found to be resistant to 2,4-D, a

phenoxy herbicide Phenoxy herbicides (or "phenoxies") are two families of chemicals that have been developed as commercially important herbicides, widely used in agriculture. They share the part structure of phenoxyacetic acid. Auxins The first group to be discover ...

. According to Bob Hartzler of

Iowa State University Iowa State University of Science and Technology (Iowa State University, Iowa State, or ISU) is a public land-grant research university in Ames, Iowa. Founded in 1858 as the Iowa Agricultural College and Model Farm, Iowa State became one of the n ...

, the most effective control of tall waterhemp is achieved by cultural practices that promote growth of the desired vegetation.

References

External links

Common Waterhemp // Mizzou WeedID

Waterhemp Take Action
{{Taxonbar, from=Q4740176 tuberculatus Flora of North America Plants described in 1849 Dioecious plants