Amaranthus tuberculatus
Encyclopedia
Amaranthus tuberculatus, commonly known as tall waterhemp or roughfruit amaranth, is a species of flowering plant
. It is a summer annual broadleaf with a germination period that lasts several months
Tall waterhemp has been reported as a weed
in 40 of 50 U.S. States
and leaves
. 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
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
s and very short bract
s with simple to highly branched flowers. Seed produced is reddish to black in colour and less than 1/32 inch in diameter.
. It is believed to have originally had a range north of Missouri
and Tennessee
to the Great Lakes
. It is now found in 40 states.
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
, 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
. Another factor contributing to genetic diversity is the large amount of seed produced. Tall waterhemp in competition with soybean
has been reported to produce from between 300,000 to 5,000,000 seed per plant. Tall waterhemp also has a rapid growth rate, 50%-70% greater than other annual weeds.
have been observed in experimental fields but have not been observed in agronomic fields.
. In Europe 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
Extension recommends a preemergence application followed by one or more postemergence applications. Tall waterhemp have been reported resistant to acetolactate synthase
inhibiting (ALS) herbicides and the triazines, with some individual weeds being resistant to both herbicides groups. Resistance 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.
According to Bob Hartzler of Iowa State University
, the most effective control of tall waterhemp is achieved by cultural practices that promote growth of the desired vegetation.
Flowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...
. It is a summer annual broadleaf with a germination period that lasts several months
Tall waterhemp has been reported as a weed
Weed
A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-controlled settings, especially farm fields and gardens, but also lawns, parks, woods, and other areas. More specifically, the term is often used to...
in 40 of 50 U.S. States
Morphology
A distinguishing characteristic of tall waterhemp that sets it apart from similar members of the genus Amaranthus is the lack of hair on its stemsPlant stem
A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...
and leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
. 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
Dioecious
Dioecy is the property of a group of biological organisms that have males and females, but not members that have organs of both sexes at the same time. I.e., those whose individual members can usually produce only one type of gamete; each individual organism is thus distinctly female or male...
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
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. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
s and very short bract
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 often different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture...
s with simple to highly branched flowers. Seed produced is reddish to black in colour and less than 1/32 inch in diameter.
Geographic distribution
Tall waterhemp is native to the United States and CanadaCanada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. It is believed to have originally had a range north of Missouri
Missouri
Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...
and Tennessee
Tennessee
Tennessee is a U.S. state located in the Southeastern United States. It has a population of 6,346,105, making it the nation's 17th-largest state by population, and covers , making it the 36th-largest by total land area...
to the Great Lakes
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...
. It is now found in 40 states.
Habitat
Tall waterhemp predominantly grows in wet habitats, such as ponds, marshes, lakes, creeks, and other riparian 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 amount of very small seed. It is considered an r-strategist. 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 application and tillage. One study observed 80% emergence not occurring until ten weeks after the initial emergence. Extreme temperatures have little effect on seed viability. GerminationGermination
Germination is the process in which a plant or fungus emerges from a seed or spore, respectively, and begins growth. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the...
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
Self-pollination is a form of pollination that can occur when a flower has both stamen and a carpel in which the cultivar or species is self fertile and the stamens and the sticky stigma of the carpel contact each other in order to accomplish pollination...
, 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
Genetic diversity, the level of biodiversity, refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary....
. Another factor contributing to genetic diversity is the large amount of seed produced. Tall waterhemp in competition with soybean
Soybean
The soybean or soya bean is a species of legume native to East Asia, widely grown for its edible bean which has numerous uses...
has been reported to produce from between 300,000 to 5,000,000 seed per plant. Tall waterhemp also has a rapid growth rate, 50%-70% greater than other annual weeds.
Interspecific hybridization
Interspecific hybrids of tall waterhemp and Amaranthus hybridusAmaranthus hybridus
Amaranthus hybridus, commonly called Smooth Amaranth, Smooth Pigweed, Red Amaranth, or Slim Amaranth, is a species of annual flowering plant. It is a weedy species found now over much of North America and introduced into Europe and Eurasia.-Description:A. hybridus grows from a short taproot and can...
have been observed in experimental fields but have not been observed in agronomic fields.
Agricultural impacts and control
In North America, tall waterhemp is considered a major weed of agricultural fields and other disturbed habitats. The Southern Weed Science Society includes tall waterhemp on their list of weed species. However, it is not listed on the federal noxious weed list or any state lists in the United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. In Europe 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 University is a public research university in East Lansing, Michigan, USA. Founded in 1855, it was the pioneer land-grant institution and served as a model for future land-grant colleges in the United States under the 1862 Morrill Act.MSU pioneered the studies of packaging,...
Extension recommends a preemergence application followed by one or more postemergence applications. Tall waterhemp have been reported resistant to acetolactate synthase
Acetolactate synthase
The acetolactate synthase enzyme 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 and the triazines, with some individual weeds being resistant to both herbicides groups. Resistance to acifluorfen
Acifluorfen
Acifluorfen is an herbicide. It is effective against broadleaf weeds and grasses and is used agriculturally on fields growing soybeans, peanuts, peas, and rice.-See also:* Lactofen, an ester derivative also used as an herbicide....
and other diphenyl ether herbicides has been reported. Even more alarming is the emergence of waterhemp resistant to the latest generation of herbicides, HPPD
4-Hydroxyphenylpyruvate dioxygenase
4-Hydroxyphenylpyruvate dioxygenase HPPD is an Fe-containing enzyme, that catalyzes the second reaction in the catabolism of tyrosine - the conversion of 4-hydroxyphenylpyruvate to homogentisate.-Function:...
inhibitors.
According to Bob Hartzler of Iowa State University
Iowa State University
Iowa State University of Science and Technology, more commonly known as Iowa State University , is a public land-grant and space-grant research university located in Ames, Iowa, United States. Iowa State has produced astronauts, scientists, and Nobel and Pulitzer Prize winners, along with a host of...
, the most effective control of tall waterhemp is achieved by cultural practices that promote growth of the desired vegetation.