Tumbleweed

Tumbleweed

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A tumbleweed is the above-ground part of a plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

 that, once mature and dry, disengages
Abscission
Abscission is a term used in several areas of biology. In plant sciences it most commonly refers to the process by which a plant drops one or more of its parts, such as a leaf, fruit, flower or seed...

 from the root and tumbles away in the wind
Wind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...

. Usually, the tumbleweed is the entire plant apart from the roots, but in a few species it is a flower cluster
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...

. The tumbleweed habit
Habit (biology)
Habit, when used in the context of biology, refers to the instinctive actions of animals and the natural tendencies of plants.In zoology, this term most often refers to specific behavioral characteristics, even when directly related to physiology...

 is most common in steppe
Steppe
In physical geography, steppe is an ecoregion, in the montane grasslands and shrublands and temperate grasslands, savannas, and shrublands biomes, characterized by grassland plains without trees apart from those near rivers and lakes...

 and desert
Desert
A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...

 climates. The tumbleweed is a diaspore
Diaspore (botany)
In botany, a diaspore is a plant dispersal unit consisting of a seed or spore plus any additional tissues that assist dispersal. In some seed plants, the diaspore is a seed and fruit together, or a seed and elaiosome. In a few seed plants, the diaspore is most or all of the plant, known as a...

, aiding in dispersal
Seed dispersal
Seed dispersal is the movement or transport of seeds away from the parent plant. Plants have limited mobility and consequently rely upon a variety of dispersal vectors to transport their propagules, including both abiotic and biotic vectors. Seeds can be dispersed away from the parent plant...

 of propagule
Propagule
In horticulture, a propagule is any plant material used for the purpose of plant propagation. In asexual reproduction, a propagule may be a woody, semi-hardwood, or softwood cutting, leaf section, or any number of other plant parts. In sexual reproduction, a propagule is a seed or spore...

s (seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

s or spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...

s). It does this by scattering the propagules either as it tumbles, or after it has come to rest in a wet location. In the latter case, the tumbleweed opens mechanically as it absorbs water; apart from its propagules, the tumbleweed is dead.

Plants forming tumbleweeds



Although the number of species with the tumbleweed habit is small, quite a number of these species are common agricultural 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...

s.

Although thought to be native to Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...

, several annual species of Salsola
Salsola
Salsola is a genus of the subfamily Salsoloideae in the family Amaranthaceae. A common name of various members of this genus is saltwort, for its salt tolerance.-Description:...

(family Amaranthaceae
Amaranthaceae
The flowering plant family Amaranthaceae, the Amaranth family, contains about 176 genera and 2,400 species.- Description :Most of these species are herbs or subshrubs; very few are trees or climbers. Some species are succulent....

) that form tumbleweeds have become so common in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 that they are a common symbol in Western
Western (genre)
The Western is a genre of various visual arts, such as film, television, radio, literature, painting and others. Westerns are devoted to telling stories set primarily in the latter half of the 19th century in the American Old West, hence the name. Some Westerns are set as early as the Battle of...

 movies, where they are typically symbolic of desolation in frontier areas. Salsola pestifera became naturalized over large areas of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 after being imported from continental Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

 often in shipments with agricultural seeds. Salsola kali
Salsola kali
Kali soda is an annual plant that grows in arid soils and in sandy coastal soils. Its original range is Eurasian, but it has become naturalized, and even invasive, in North America, Australia, and elsewhere...

is said to have arrived in the United States in shipments of flax
Flax
Flax is a member of the genus Linum in the family Linaceae. It is native to the region extending from the eastern Mediterranean to India and was probably first domesticated in the Fertile Crescent...

 seeds to South Dakota
South Dakota
South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...

 in the nineteenth century.

Salsola tragus
Salsola tragus
Kali tragus is a species of flowering plant in the amaranth family known by the common name prickly Russian thistle, or simply Russian thistle. It is perhaps the most common species of tumbleweed, and may be known by this general name...

is an annual plant that breaks off at the stem
Plant 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...

 base, forming a tumbleweed that disperses its seeds as it rolls on top of the ground. It seems to have been imported into South Dakota from Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

 in 1870 or 1874 in shipments of flaxseed. It has become a noxious weed that has spread throughout North America to inhabit suitable habitats which include areas with disturbed soils like roadsides, cultivated fields and eroded slopes, and in natural habitats that have sparse vegetation like coastal and riparian sands, semi-deserts and deserts. Salsola tragus is the correct name for the narrow-leaved, weedy representative of the S. kali aggregate found widely over North America. It is an extremely variable species with many races which vary in distinctness, some of these varieties in the past have been divided into subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

 or even separate species. Though it is a noxious weed, Salsola tragus is useful on arid rangelands as forage for livestock.

Other members of the family Amaranthaceae that form tumbleweeds include Amaranthus albus
Amaranthus albus
Amaranthus albus is an annual species of flowering plant. It is native to the tropical Americas but a widespread introduced species in other places, including Europe, Africa, and Australia...

, native to Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

 but introduced and weedy in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

, and Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

; Amaranthus graecizans
Amaranthus graecizans
Amaranthus graecizans is an African species in the botanical family Amaranthaceae. It is naturalized in North America.Common names include tumbleweed and pigweed. page 27The edible leaves are used as a vegetable throughout Africa....

naturalized to North America from its native Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

; Amaranthus retroflexus
Amaranthus retroflexus
Amaranthus retroflexus is a species of flowering plant in the Amaranthaceae family with several common names, including Red-root Amaranth, Redroot Pigweed, Red Rooted Pigweed, Common Amaranth, and common tumble weed....

; Corispermum hyssopifolium; Kochia
Kochia
Kochia is a synonym of the genus Bassia, that belongs to the subfamily Camphorosmoideae of family Amaranthaceae.Two american species traditionally included in Kochia are now in genus Neokochia: Neokochia americana and Neokochia californica....

; and Cycloloma atriplicifolium, which is called the plains tumbleweed.

Atriplex rosea
Atriplex rosea
Atriplex rosea is a species of saltbush known by the common names tumbling saltbush, red orach, and tumbling orach. It is native to Eurasia but it is widespread elsewhere as an introduced species....

called the tumbling oracle or tumbling orach, is a member of the Chenopodiaceae
Chenopodiaceae
Chenopodiaceae were a family of flowering plants, also called the Goosefoot Family. They are now included within family Amaranthaceae. The vast majority of Chenopods are weeds, and many are salt and drought tolerant. A few food crops also belong to the family: spinach, beets, chard, quinoa, and...

.

In the aster family (Asteraceae
Asteraceae
The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...

), Centaurea diffusa (a knapweed) forms tumbleweeds. This species is native to Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...

 and naturalized in much of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

. Also in this family, Lessingia glandulifera
Lessingia glandulifera
Lessingia glandulifera is a species of flowering plant in the daisy family known by the common name valley lessingia. It is native to California and Baja California, where it grows in several types of habitat, from forest and desert to the coastline. This is an annual herb varying in maximum size...

sometimes forms tumbleweeds; it grows in desert areas, chaparral, and open pine forests of the western United States and is usually found on sandy soils.

In the legume family (Fabaceae
Fabaceae
The Fabaceae or Leguminosae, commonly known as the legume, pea, or bean family, is a large and economically important family of flowering plants. The group is the third largest land plant family, behind only the Orchidaceae and Asteraceae, with 730 genera and over 19,400 species...

), species reported to produce tumbleweeds include some members of the genus Psoralea
Psoralea
Psoralea is a genus in the legume family . Although most species are poisonous, the starchy roots of P. esculenta and P. hypogaea are edible...

, and Baptisia tinctoria
Baptisia tinctoria
Baptisia tinctoria is a herbaceous perennial plant in the family Fabaceae. It is native to eastern North America.-Distribution:...

.

In the plantain family (Plantaginaceae
Plantaginaceae
Plantaginaceae Juss. or plantain family, are a family of flowering plants in the order Lamiales. The type genus is Plantago L..In older classifications it used to be the only family of the order Plantaginales, but numerous phylogenetic studies, summarized by the Angiosperm Phylogeny Group, have...

), Plantago cretica
Plantago cretica
Plantago cretica is a species of Plantago, family Plantaginaceae....

.

In the Solanaceae
Solanaceae
Solanaceae are a family of flowering plants that include a number of important agricultural crops as well as many toxic plants. The name of the family comes from the Latin Solanum "the nightshade plant", but the further etymology of that word is unclear...

, Solanum rostratum
Solanum rostratum
Solanum rostratum is a species of nightshade that is native to the United States and northern and central Mexico. Common names include buffalo bur, spiny nightshade, and Texas thistle....

.

In the mustard family (Brassicaceae
Brassicaceae
Brassicaceae, a medium sized and economically important family of flowering plants , are informally known as the mustards, mustard flowers, the crucifers or the cabbage family....

), Sisymbrium altissimum
Sisymbrium altissimum
Sisymbrium altissimum is a species of Sisymbrium. The plant is native to the western part of the Mediterranean Basin in Europe and Northern Africa and is widely naturalized throughout most of the world, including all of North America. It was probably introduced into North America by a contaminant...

, Crambe maritima, Lepidium
Lepidium
Lepidium is a genus of plants in the mustard family Brassicaceae. It includes about 175 species found worldwide, including cress and pepperweed; additional common names include peppercress, peppergrass, and pepperwort...

, and Anastatica (a resurrection plant
Resurrection plant
A resurrection plant is any plant with the habit of reviving after seeming to be dead or of seeming to revive when being in fact dead.Examples include...

) form tumbleweeds. Very similar in habit to Anastatica, but very distantly related, are the spore-bearing Selaginella lepidophylla
Selaginella lepidophylla
Selaginella lepidophylla is a species of desert plant in the spikemoss family . S. lepidophylla is noted for its ability to survive almost complete desiccation; during dry weather in its native habitat, its stems curl into a tight ball and uncurl when exposed to moisture...

(a lycopod
Lycopodiophyta
The Division Lycopodiophyta is a tracheophyte subdivision of the Kingdom Plantae. It is the oldest extant vascular plant division at around 410 million years old, and includes some of the most "primitive" extant species...

) and earthstar mushroom family (Geastraceae
Geastraceae
The earthstars are the family Geastraceae of gasterocarpic basidiomycetes . It includes the genera Geastrum and Myriostoma. About sixty-four species are classified in this family, divided among eight genera....

). All of these curl into a ball when dry, and uncurl when moistened.

A tumbleweed formed from the flower cluster (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...

) occurs in some species of the parsley family (Apiaceae
Apiaceae
The Apiaceae , commonly known as carrot or parsley family, is a group of mostly aromatic plants with hollow stems. The family is large, with more than 3,700 species spread across 434 genera, it is the sixteenth largest family of flowering plants...

).

The garden plant "baby's-breath" (Gypsophila paniculata
Gypsophila paniculata
Gypsophila paniculata, commonly known as Baby's-breath, is a cultivated ornamental garden plant in the Caryophyllaceae family, popular in the florist trade to provide a background for more colourful flowers....

), which is in the pink family Caryophyllaceae
Caryophyllaceae
The Caryophyllaceae, commonly called the pink family or carnation family, is a family of flowering plants. It is included in the dicotyledon order Caryophyllales in the APG III system, alongside 33 other families, including Amaranthaceae, Cactaceae and Polygonaceae...

, has a dry inflorescence that forms tumbleweeds. In parts of central and western North America, it has become a common weed in many locations including hayfields and pastures.

Anatomy


In some species, the tumbleweed is detached from the plant by abscission
Abscission
Abscission is a term used in several areas of biology. In plant sciences it most commonly refers to the process by which a plant drops one or more of its parts, such as a leaf, fruit, flower or seed...

 of the plant stem
Plant 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...

; abscission has been shown in Psoralea and Kochia.

Similar diaspores


Diaspores made of inflorescences occur also in some grasses
Poaceae
The Poaceae is a large and nearly ubiquitous family of flowering plants. Members of this family are commonly called grasses, although the term "grass" is also applied to plants that are not in the Poaceae lineage, including the rushes and sedges...

, including Schedonnardus paniculatus and some species of Eragrostis and Aristida. In these plants, the inflorescences break off and tumble in the wind instead of the whole plant. The species of Spinifex
Spinifex (genus)
Spinifex is a genus of perennial coastal grasses. They are one of the most common plants that grow in sand dunes along the coasts of Australia, New Zealand and New Caledonia.. As they help stabilise the sand, these grasses are an important part of the entire sand dune ecosystem. Of the four species...

from Southeast Asia are prominent examples of this dispersal adaptation. These grasses are often called tumble-grasses, including such species as Panicum capillare
Panicum capillare
Panicum capillare, known by the common name Witchgrass, is a species of grass. It is native plant to most of North America from the East Coast through all of the West Coast and California. It can be found as an introduced species in Eurasia, and as a weed in gardens and landscaped areas...

and Eragrostis pectinacea
Eragrostis pectinacea
Eragrostis pectinacea is a species of grass known by the common name Tufted lovegrass. This plant is native to the Americas from Canada to Argentina...

in the United States.

In Southern Africa genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of Amaryllidaceae
Amaryllidaceae
Amaryllidoideae is the subfamily of flowering plants that takes its name from the genus Amaryllis. It is part of the family Amaryllidaceae, in order Asparagales...

 such as Boophane
Boophone
Boophone is a genus of herbaceous, perennial and bulbous plants in the Amaryllis family . It consists of two species distributed in Tropical and Southern Africa...

, Crossyne, and to a lesser extent Brunsvigia
Brunsvigia
Brunsvigia is a flowering plant genus in the family Amaryllidaceae, subfamily Amaryllidoideae. It contains about 20 species native to South Africa....

, bear inflorescences in the form of globular umbels with long, spoke-like pedicels, either effectively at ground level, or breaking off once the stems are dry and the seeds ripe. The light, open, globular structures form very effective tumbleweed diaspores, dropping the seeds usually within a few days as the follicles fail under the wear of rolling. The seeds are fleshy, short-lived, and germinate rapidly where they land. Being poisonous and distasteful, they are not attractive to candidate transport animals, so the rolling diaspore is a very effective strategy for such plants.

Wind dispersed fruits that tumble or roll on the ground, sometimes known as "tumble fruits", are rare. Some are technically achenes. Highly inflated indehiscent fruits that may facilitate tumbling include Alyssopsis, Coluteocarpus, Physoptychis, and Physaria
Physaria
Physaria is a genus of flowering plants in the mustard family. Many species are known generally as twinpods. They are native to the Americas, with many species endemic to western North America. They are densely hairy perennial herbs often growing prostrate or decumbent, along the ground in patches...

.

Environmental effects



Tumbleweeds have a significant effect on wind soil erosion in open regions, particularly on dry-land agricultural operations where the outside application of additional moisture is impossible. One study showed that a single Russian Thistle can remove up to 44 gallons of water from the soil while competing with a wheat crop. The amount of water removed from fallow land more subject to erosion would be even higher. In addition to the moisture consumed by the plant, significant damage to the protective soil crust is caused by the tumbleweeds' motion. The damage to the soil surface then provides exposure for subsequent wind damage and topsoil loss.

Symbolism


The tumbleweed's association with the Western
Western (genre)
The Western is a genre of various visual arts, such as film, television, radio, literature, painting and others. Westerns are devoted to telling stories set primarily in the latter half of the 19th century in the American Old West, hence the name. Some Westerns are set as early as the Battle of...

 film has led to a highly symbolic meaning in visual media. It has come to represent locations that are desolate, dry, and often humorless, with few or no occupants. A common use is when characters encounter a long abandoned or dismal-looking place: a tumbleweed will be seen rolling past, often accompanied by the sound of a hollow, dry wind. This is sometimes used in locations where tumbleweeds are not expected, for comedic effect. It is also sometimes used to punctuate a bad joke or a character otherwise making an absurd declaration, with the plant rolling past in the background and the wind effect emphasizing the awkward silence (similar to the sound of crickets).

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