Weaving is a method of textile production in which two distinct sets of yarns or threads are interlaced at right angles to form a fabric or cloth. Other methods are knitting, crocheting and braiding or plaiting; the longitudinal threads are called the warp and the lateral threads are the weft or filling. The method in which these threads are inter-woven affects the characteristics of the cloth. Cloth is woven on a loom, a device that holds the warp threads in place while filling threads are woven through them. A fabric band which meets this definition of cloth can be made using other methods, including tablet weaving, back strap loom, or other techniques without looms; the way the warp and filling threads interlace with each other is called the weave. The majority of woven products are created with one of three basic weaves: plain weave, satin weave, or twill. Woven cloth can be woven in decorative or artistic design. In general, weaving involves using a loom to interlace two sets of threads at right angles to each other: the warp which runs longitudinally and the weft that crosses it.
One warp thread is called. The warp threads are held taut and in parallel to each other in a loom. There are many types of looms. Weaving can be summarized as a repetition of these three actions called the primary motion of the loom. Shedding: where the warp threads are separated by raising or lowering heald frames to form a clear space where the pick can pass Picking: where the weft or pick is propelled across the loom by hand, an air-jet, a rapier or a shuttle. Beating-up or battening: where the weft is pushed up against the fell of the cloth by the reed; the warp is divided into two overlapping groups, or lines that run in two planes, one above another, so the shuttle can be passed between them in a straight motion. The upper group is lowered by the loom mechanism, the lower group is raised, allowing to pass the shuttle in the opposite direction in a straight motion. Repeating these actions form a fabric mesh but without beating-up, the final distance between the adjacent wefts would be irregular and far too large.
The secondary motion of the loom are the: Let off Motion: where the warp is let off the warp beam at a regulated speed to make the filling and of the required design Take up Motion: Takes up the woven fabric in a regulated manner so that the density of filling is maintainedThe tertiary motions of the loom are the stop motions: to stop the loom in the event of a thread break. The two main stop motions are the warp stop motion weft stop motionThe principal parts of a loom are the frame, the warp-beam or weavers beam, the cloth-roll, the heddles, their mounting, the reed; the warp-beam is a wooden or metal cylinder on the back of the loom. The threads of the warp extend in parallel order from the warp-beam to the front of the loom where they are attached to the cloth-roll; each thread or group of threads of the warp passes through an opening in a heddle. The warp threads are separated by the heddles into two or more groups, each controlled and automatically drawn up and down by the motion of the heddles.
In the case of small patterns the movement of the heddles is controlled by "cams" which move up the heddles by means of a frame called a harness. Where a complex design is required, the healds are raised by harness cords attached to a Jacquard machine; every time the harness moves up or down, an opening is made between the threads of warp, through which the pick is inserted. Traditionally the weft thread is inserted by a shuttle. On a conventional loom, the weft thread is carried on a pirn, in a shuttle that passes through the shed. A handloom weaver could propel the shuttle by throwing it from side to side with the aid of a picking stick; the "picking" on a power loom is done by hitting the shuttle from each side using an overpick or underpick mechanism controlled by cams 80–250 times a minute. When a pirn is depleted, it is ejected from the shuttle and replaced with the next pirn held in a battery attached to the loom. Multiple shuttle boxes allow more than one shuttle to be used; each can carry a different colour.
The rapier-type weaving machines do not have shuttles, they propel the weft by means of small grippers or rapiers that pick up the filling thread and carry it halfway across the loom where another rapier picks it up and pulls it the rest of the way. Some carry the filling yarns across the loom at rates in excess of 2,000 metres per minute. Manufacturers such as Picanol have reduced the mechanical adjustments to a minimum, control all the functions through a computer with a graphical user interface. Other types use compressed air to insert the pick, they are all fast and quiet. The warp is sized in a starch mixture for smoother running; the loom warped by passing the sized warp threads through two or more heddles attached to harnesses. The power weavers. Most looms used for industrial purposes have a machine that ties new warps threads to the waste of used warps threads, while still on the loom an operator rolls the old and new threads back on the warp beam; the harnesses are controlled by dobbies or a Jacquard head.
The raising and lowering
Cincinnati is a major city in the U. S. state of Ohio, is the government seat of Hamilton County. Settled in 1788, the city is located at the northern side of the confluence of the Licking and Ohio rivers, the latter of which marks the state line with Kentucky; the city drives the Cincinnati–Middletown–Wilmington combined statistical area, which had a population of 2,172,191 in the 2010 census making it Ohio's largest metropolitan area. With a population of 296,943, Cincinnati is the third-largest city in Ohio and 65th in the United States, its metropolitan area is the fastest growing economic power in the Midwestern United States based on increase of economic output and it is the 28th-largest metropolitan statistical area in the U. S. Cincinnati is within a day's drive of 49.70% of the United States populace. In the nineteenth century, Cincinnati was an American boomtown in the middle of the country. Throughout much of the 19th century, it was listed among the top 10 U. S. cities by population, surpassed only by New Orleans and the older, established settlements of the United States eastern seaboard, as well as being the sixth-biggest city for a period spanning 1840 until 1860.
As Cincinnati was the first city founded after the American Revolution, as well as the first major inland city in the country, it is regarded as the first purely "American" city. Cincinnati developed with fewer immigrants and less influence from Europe than East Coast cities in the same period. However, it received a significant number of German immigrants, who founded many of the city's cultural institutions. By the end of the 19th century, with the shift from steamboats to railroads drawing off freight shipping, trade patterns had altered and Cincinnati's growth slowed considerably; the city was surpassed in population by other inland cities Chicago, which developed based on strong commodity exploitation and the railroads, St. Louis, which for decades after the Civil War served as the gateway to westward migration. Cincinnati is home to three major sports teams: the Cincinnati Reds of Major League Baseball; the city's largest institution of higher education, the University of Cincinnati, was founded in 1819 as a municipal college and is now ranked as one of the 50 largest in the United States.
Cincinnati is home to historic architecture with many structures in the urban core having remained intact for 200 years. In the late 1800s, Cincinnati was referred to as the "Paris of America", due to such ambitious architectural projects as the Music Hall, Cincinnatian Hotel, Shillito Department Store. Cincinnati is the birthplace of the 27th President of the United States. Cincinnati began in 1788 when Mathias Denman, Colonel Robert Patterson, Israel Ludlow landed at a spot at the northern bank of the Ohio opposite the mouth of the Licking and decided to settle there; the original surveyor, John Filson, named it "Losantiville". In 1790, Arthur St. Clair, the governor of the Northwest Territory, changed the name of the settlement to "Cincinnati" in honor of the Society of the Cincinnati, made up of Revolutionary War veterans, of which he was a member; the introduction of steamboats on the Ohio River in 1811 opened up the city's trade to more rapid shipping, the city established commercial ties with St. Louis and New Orleans downriver.
Cincinnati was incorporated as a city on March 1, 1819. Exporting pork products and hay, it became a center of pork processing in the region. From 1810 to 1830 its population nearly tripled, from 9,642 to 24,831. Completion of the Miami and Erie Canal in 1827 to Middletown, Ohio further stimulated businesses, employers struggled to hire enough people to fill positions; the city had a labor shortage until large waves of immigration by Irish and Germans in the late 1840s. The city grew over the next two decades, reaching 115,000 people by the year 1850. Construction on the Miami and Erie Canal began on July 21, 1825, when it was called the Miami Canal, related to its origin at the Great Miami River; the first section of the canal was opened for business in 1827. In 1827, the canal connected Cincinnati to nearby Middletown. During this period of rapid expansion and prominence, residents of Cincinnati began referring to the city as the Queen City. After the steamboats, railroads were the next major form of commercial transportation to come to Cincinnati.
In 1836, the Little Miami Railroad was chartered. Construction began soon after, to connect Cincinnati with the Mad River and Lake Erie Railroad, provide access to the ports of the Sandusky Bay on Lake Erie. Cincinnati acted as a "border town" during the slave-owning period between 1810 and 1863, its location, on the border between the free state of Ohio and the slave state of Kentucky, made it a prominent location for slaves to escape the slave-owning south. Many prominent abolitionists called Cincinnati their home during this period, made it a popular stop on the Underground Railroad. In 2004, the National Underground Railroad Freedom Center was completed along Freedom Way in Downtown, honoring the city's past involvement in the Underground Railroad. In 1859, Cincinnati laid out six streetcar lines. By 1872, Cincinnatians could travel on the streetcars within the city and transfer to rail cars for travel to the hill communities; the Cincinnati Inclined Plane Company began transporting people t
Yarn is a long continuous length of interlocked fibres, suitable for use in the production of textiles, crocheting, weaving, embroidery, or ropemaking. Thread is a type of yarn intended for sewing by machine. Modern manufactured sewing threads may be finished with wax or other lubricants to withstand the stresses involved in sewing. Embroidery threads are yarns designed for needlework; the word yarn comes from Middle English, from the Old English gearn, akin to Old High German's garn yarn, Greek's chordē string, Sanskrit's hira band. Yarn can be made from a number of synthetic fibers. Many types of yarn are made differently though. There are two main types of yarn: spun and filament; the most common plant fiber is cotton, spun into fine yarn for mechanical weaving or knitting into cloth. Cotton and polyester are the most spun fibers in the world. Cotton is grown throughout the world. After harvesting it is prepared for yarn spinning. Polyester is extruded from polymers derived from natural oil. Synthetic fibers are extruded in continuous strands of gel-state materials.
These strands are drawn and cured to obtain properties desirable for processing. Synthetic fibers come in three basic forms: staple and filament. Staple is cut fibers sold in lengths up to 120mm. Tow is a continuous "rope" of fibers consisting of many filaments loosely joined side-to-side. Filament is a continuous strand consisting of anything from 1 filament to many. Synthetic fiber is most measured in a weight per linear measurement basis, along with cut length. Denier and Dtex are the most common weight to length measures. Cut-length only applies to staple fiber. Filament extrusion is sometimes referred to as "spinning" but most people equate spinning with spun yarn production; the most spun animal fiber is wool harvested from sheep. For hand knitting and hobby knitting, thick and acrylic yarns are used. Other animal fibers used include alpaca, mohair, llama and silk. More yarn may be spun from camel, possum, musk ox, dog, rabbit, or buffalo hair, turkey or ostrich feathers. Natural fibers such as these have the advantage of being elastic and breathable, while trapping a great deal of air, making for a warm fabric.
Other natural fibers that can be used for yarn include cotton. These tend to be much less elastic, retain less warmth than the animal-hair yarns, though they can be stronger in some cases; the finished product will look rather different from the woolen yarns. Other plant fibers which can be spun include bamboo, corn and soy fiber. T-shirt yarn is a yarn made directly from t-shirts, the fiber composition is determined by the material the t-shirt is made from. In general, natural fibers tend to require more careful handling than synthetics because they can shrink, stain, fade, wrinkle, or be eaten by moths more unless special treatments such as mercerization or superwashing are performed to strengthen, fix color, or otherwise enhance the fiber's own properties. Protein yarns may be irritating to some people, causing contact dermatitis, wheezing, or other reactions. Plant fibers tend to be better tolerated by people with sensitivities to the protein yarns, allergists may suggest using them or synthetics instead to prevent symptoms.
Some people find that they can tolerate organically grown and processed versions of protein fibers because organic processing standards preclude the use of chemicals that may irritate the skin. When natural hair-type fibers are burned, they tend to have a smell of burnt hair. Cotton and viscose yarns burn as a wick. Synthetic yarns tend to melt though some synthetics are inherently flame-retardant. Noting how an unidentified fiber strand burns and smells can assist in determining if it is natural or synthetic, what the fiber content is. Both synthetic and natural yarns can pill. Pilling is a function of fiber content, spinning method, contiguous staple length, fabric construction. Single ply yarns or using fibers like merino wool are known to pill more due to the fact that in the former, the single ply is not tight enough to securely retain all the fibers under abrasion, the merino wool's short staple length allows the ends of the fibers to pop out of the twist more easily. Yarns combining synthetic and natural fibers inherit the properties of each parent, according to the proportional composition.
Synthetics are added to lower cost, increase durability, add unusual color or visual effects, provide machine washability and stain resistance, reduce heat retention or lighten garment weight. Spun yarn is made by twisting staple fibres together to make a cohesive thread, or "single." Twisting fibres into yarn in the process called spinning can be dated back to the Upper Paleolithic, yarn spinning was one of the first processes to be industrialized. Spun yarns may be a blend of various types. Combining synthetic fibres with natural fibres is common; the most used blends are cotton-polyester and wool-acrylic fibre blends. Blends of different natural fibres are common too with more expensive fibres such as alpaca and cashmere. Yarn is selected for different textiles based on the characteristics of the yarn fibres, such as warmth, light weight, durability (nylo
International Union for Conservation of Nature
The International Union for Conservation of Nature is an international organization working in the field of nature conservation and sustainable use of natural resources. It is involved in data gathering and analysis, field projects and education. IUCN's mission is to "influence and assist societies throughout the world to conserve nature and to ensure that any use of natural resources is equitable and ecologically sustainable". Over the past decades, IUCN has widened its focus beyond conservation ecology and now incorporates issues related to sustainable development in its projects. Unlike many other international environmental organisations, IUCN does not itself aim to mobilize the public in support of nature conservation, it tries to influence the actions of governments and other stakeholders by providing information and advice, through building partnerships. The organization is best known to the wider public for compiling and publishing the IUCN Red List of Threatened Species, which assesses the conservation status of species worldwide.
IUCN has a membership of over 1400 non-governmental organizations. Some 16,000 scientists and experts participate in the work of IUCN commissions on a voluntary basis, it employs 1000 full-time staff in more than 50 countries. Its headquarters are in Switzerland. IUCN has observer and consultative status at the United Nations, plays a role in the implementation of several international conventions on nature conservation and biodiversity, it was involved in establishing the World Wide Fund for Nature and the World Conservation Monitoring Centre. In the past, IUCN has been criticized for placing the interests of nature over those of indigenous peoples. In recent years, its closer relations with the business sector have caused controversy. IUCN was established in 1948, it was called the International Union for the Protection of Nature and the World Conservation Union. Establishment IUCN was established on 5 October 1948, in Fontainebleau, when representatives of governments and conservation organizations signed a formal act constituting the International Union for the Protection of Nature.
The initiative to set up the new organisation came from UNESCO and from its first Director General, the British biologist Julian Huxley. The objectives of the new Union were to encourage international cooperation in the protection of nature, to promote national and international action and to compile and distribute information. At the time of its founding IUPN was the only international organisation focusing on the entire spectrum of nature conservation Early years: 1948–1956 IUPN started out with 65 members, its secretariat was located in Brussels. Its first work program focused on saving species and habitats and applying knowledge, advancing education, promoting international agreements and promoting conservation. Providing a solid scientific base for conservation action was the heart of all activities. IUPN and UNESCO were associated, they jointly organized the 1949 Conference on Protection of Nature. In preparation for this conference a list of gravely endangered species was drawn up for the first time, a precursor of the IUCN Red List of Threatened Species.
In the early years of its existence IUCN depended entirely on UNESCO funding and was forced to temporarily scale down activities when this ended unexpectedly in 1954. IUPN was successful in engaging prominent scientists and identifying important issues such as the harmful effects of pesticides on wildlife but not many of the ideas it developed were turned into action; this was caused by unwillingness to act on the part of governments, uncertainty about the IUPN mandate and lack of resources. In 1956, IUPN changed its name to International Union for Conservation of Nature and Natural Resources. Increased profile and recognition: 1956–1965 In the 1950s and 1960s Europe entered a period of economic growth and formal colonies became independent. Both developments had impact on the work of IUCN. Through the voluntary involvement of experts in its Commissions IUCN was able to get a lot of work done while still operating on a low budget, it established links with the Council of Europe. In 1961, at the request of United Nations Economic and Social Council, the United Nations Economic and Social Council, IUCN published the first global list of national parks and protected areas which it has updated since.
IUCN's best known publication, the Red Data Book on the conservation status of species, was first published in 1964. IUCN began to play a part in the development of international treaties and conventions, starting with the African Convention on the Conservation of Nature and Natural Resources. Environmental law and policy making became a new area of expertise. Africa was the focus of many of the early IUCN conservation field projects. IUCN supported the ‘Yellowstone model’ of protected area management, which restricted human presence and activity in order to protect nature. IUCN and other conservation organisations were criticized for protecting nature against people rather than with people; this model was also applied in Africa and played a role in the decision to remove the Maasai people from Serengeti National Park and the Ngorongoro Conservation Area. To establish a stable financial basis for its work, IUCN participated in setting up the World Wildlife Fund
Knitting is a method by which yarn is manipulated to create a textile or fabric used in many types of garments. Knitting creates multiple loops of yarn, called stitches, in a line or tube. Knitting has multiple active stitches on the needle at one time. Knitted fabric consists of a number of consecutive rows of intermeshing of loops; as each row progresses, a newly created loop is pulled through one or more loops from the prior row, placed on the gaining needle, the loops from the prior row are pulled off the other needle. Knitting may be done by using a machine. Different types of yarns, needle sizes, stitch types may be used to achieve knitted fabrics with different properties. Like weaving, knitting is a technique for producing a two-dimensional fabric made from a one-dimensional yarn or thread. In weaving, threads are always straight, running parallel either crosswise. By contrast, the yarn in knitted fabrics follows a meandering path, forming symmetric loops symmetrically above and below the mean path of the yarn.
These meandering loops can be stretched in different directions giving knit fabrics much more elasticity than woven fabrics. Depending on the yarn and knitting pattern, knitted garments can stretch as much as 500%. For this reason, knitting was developed for garments that must be elastic or stretch in response to the wearer's motions, such as socks and hosiery. For comparison, woven garments stretch along one or other of a related pair of directions that lie diagonally between the warp and the weft, while contracting in the other direction of the pair, are not elastic, unless they are woven from stretchable material such as spandex. Knitted garments are more form-fitting than woven garments, since their elasticity allows them to contour to the body's outline more closely. Extra curvature can be introduced into knitted garments without seams, as in the heel of a sock. Thread used in weaving is much finer than the yarn used in knitting, which can give the knitted fabric more bulk and less drape than a woven fabric.
If they are not secured, the loops of a knitted course will come undone. To secure a stitch, at least one new loop is passed through it. Although the new stitch is itself unsecured, it secures the stitch suspended from it. A sequence of stitches in which each stitch is suspended from the next is called a wale. To secure the initial stitches of a knitted fabric, a method for casting on is used. During knitting, the active stitches are secured mechanically, either from individual hooks or from a knitting needle or frame in hand-knitting. There are two major varieties of knitting: weft knitting and warp knitting. In the more common weft knitting, the wales are perpendicular to the course of the yarn. In warp knitting, the wales and courses run parallel. In weft knitting, the entire fabric may be produced from a single yarn, by adding stitches to each wale in turn, moving across the fabric as in a raster scan. By contrast, in warp knitting, one yarn is required for every wale. Since a typical piece of knitted fabric may have hundreds of wales, warp knitting is done by machine, whereas weft knitting is done by both hand and machine.
Warp-knitted fabrics such as tricot and milanese are resistant to runs, are used in lingerie. Weft-knit fabrics may be knit with multiple yarns to produce interesting color patterns; the two most common approaches are intarsia and stranded colorwork. In intarsia, the yarns are used in well-segregated regions. In the more complex stranded approach, two or more yarns alternate within one row and all the yarns must be carried along the row, as seen in Fair Isle sweaters. Double knitting can produce two separate knitted fabrics simultaneously. However, the two fabrics are integrated into one, giving it great warmth and excellent drape. In securing the previous stitch in a wale, the next stitch can pass through the previous loop from either below or above. If the former, the stitch is denoted as a ` plain stitch; the two stitches are related in that a knit stitch seen from one side of the fabric appears as a purl stitch on the other side. The two types of stitches have a different visual effect. Patterns and pictures can be created in knitted fabrics by using knit and purl stitches as "pixels".
Individual stitches, or rows of stitches, may be made taller by drawing more yarn into the new loop, the basis for uneven knitting: a row of tall stitches may alternate with one or more rows of short st
Alabama is a state in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east and the Gulf of Mexico to the south, Mississippi to the west. Alabama is the 30th largest by area and the 24th-most populous of the U. S. states. With a total of 1,500 miles of inland waterways, Alabama has among the most of any state. Alabama is nicknamed the Yellowhammer State, after the state bird. Alabama is known as the "Heart of Dixie" and the "Cotton State"; the state tree is the longleaf pine, the state flower is the camellia. Alabama's capital is Montgomery; the largest city by population is Birmingham. The oldest city is Mobile, founded by French colonists in 1702 as the capital of French Louisiana. From the American Civil War until World War II, like many states in the southern U. S. suffered economic hardship, in part because of its continued dependence on agriculture. Similar to other former slave states, Alabamian legislators employed Jim Crow laws to disenfranchise and otherwise discriminate against African Americans from the end of the Reconstruction Era up until at least the 1970s.
Despite the growth of major industries and urban centers, white rural interests dominated the state legislature from 1901 to the 1960s. During this time, urban interests and African Americans were markedly under-represented. Following World War II, Alabama grew as the state's economy changed from one based on agriculture to one with diversified interests; the state's economy in the 21st century is based on management, finance, aerospace, mineral extraction, education and technology. The European-American naming of the Alabama River and state was derived from the Alabama people, a Muskogean-speaking tribe whose members lived just below the confluence of the Coosa and Tallapoosa rivers on the upper reaches of the river. In the Alabama language, the word for a person of Alabama lineage is Albaamo; the suggestion that "Alabama" was borrowed from the Choctaw language is unlikely. The word's spelling varies among historical sources; the first usage appears in three accounts of the Hernando de Soto expedition of 1540: Garcilaso de la Vega used Alibamo, while the Knight of Elvas and Rodrigo Ranjel wrote Alibamu and Limamu in transliterations of the term.
As early as 1702, the French called the tribe the Alibamon, with French maps identifying the river as Rivière des Alibamons. Other spellings of the name have included Alibamu, Albama, Alibama, Alabamu, Allibamou. Sources disagree on the word's meaning; some scholars suggest the word comes from amo. The meaning may have been "clearers of the thicket" or "herb gatherers", referring to clearing land for cultivation or collecting medicinal plants; the state has numerous place names of Native American origin. However, there are no correspondingly similar words in the Alabama language. An 1842 article in the Jacksonville Republican proposed it meant "Here We Rest." This notion was popularized in the 1850s through the writings of Alexander Beaufort Meek. Experts in the Muskogean languages have not found any evidence to support such a translation. Indigenous peoples of varying cultures lived in the area for thousands of years before the advent of European colonization. Trade with the northeastern tribes by the Ohio River began during the Burial Mound Period and continued until European contact.
The agrarian Mississippian culture covered most of the state from 1000 to 1600 AD, with one of its major centers built at what is now the Moundville Archaeological Site in Moundville, Alabama. This is the second-largest complex of the classic Middle Mississippian era, after Cahokia in present-day Illinois, the center of the culture. Analysis of artifacts from archaeological excavations at Moundville were the basis of scholars' formulating the characteristics of the Southeastern Ceremonial Complex. Contrary to popular belief, the SECC appears to have no direct links to Mesoamerican culture, but developed independently; the Ceremonial Complex represents a major component of the religion of the Mississippian peoples. Among the historical tribes of Native American people living in present-day Alabama at the time of European contact were the Cherokee, an Iroquoian language people. While part of the same large language family, the Muskogee tribes developed distinct cultures and languages. With exploration in the 16th century, the Spanish were the first Europeans to reach Alabama.
The expedition of Hernando de Soto passed through Mabila and other parts of the state in 1540. More than 160 years the French founded the region's first European settlement at Old Mobile in 1702; the city was moved to the current site of Mobile in 1711. This area was claimed by the French from 1702 to 1763 as part of La Louisiane. After the French lost to the British in the Seven Years' War, it became part of British West Florida from 1763 to 1783. After the United States victory in the American Revolutionary War, the territory was divided between the United States and Spain; the latter retained control of this western territory from 1783 until the surrender of the Spanish garrison at Mobile to U. S. forces on April 13, 1813. Thomas Bassett, a loyalist to the British monarchy during the Revolutionary era, was one of the earliest white settlers in the state
Fraxinus pennsylvanica, the green ash or red ash, is a species of ash native to eastern and central North America, from Nova Scotia west to southeastern Alberta and eastern Colorado, south to northern Florida, southwest to Oklahoma and eastern Texas. It has spread and become naturalized in much of the western United States and in Europe from Spain to Russia. Other names more used include downy ash, swamp ash and water ash. Fraxinus pennsylvanica is a medium-sized deciduous tree reaching 12–25 m tall with a trunk up to 60 cm in diameter; the bark is gray on young trees, becoming thick and fissured with age. The winter buds are reddish-brown, with a velvety texture; the leaves are 15–30 cm long, pinnately compound with seven to nine leaflets, these 5–15 cm long and 1.2–9 cm broad, with serrated margins and short but distinct, downy petiolules a few millimeters long. They are green both below; the autumn color is golden-yellow and depending on the climate, Green Ash's leaves may begin changing color the first week of September.
The flowers are produced in spring in compact panicles. The fruit is a samara 2.5–7.5 cm long comprising a single seed 1.5–3 cm long with an elongated apical wing 2–4 cm long and 3–7 mm broad. It is sometimes divided into two varieties, Fraxinus pennsylvanica var. pennsylvanica and Fraxinus pennsylvanica var. lanceolata Sarg. on the basis of the hairless leaves with narrower leaflets of the latter, but the two intergrade and the distinction is no longer upheld by most botanists. It is the most distributed of all the American ashes, although its range centers on the midwestern U. S. and Great Plains. The natural habitat of green ash is exclusively stream sides and bottomlands; the large seed crops provide food to many kinds of wildlife. Green ash is threatened by the emerald ash borer, a beetle introduced accidentally from Asia. Asian ashes have a high tannin content in their leaves which makes them unpalatable to the beetle, while most American species do not. A common garden experiment showed that green ash is killed when exposed to emerald ash borer, while the Asian species F. mandschurica shows resistance against emerald ash borer.
The United States Forest Service has discovered small numbers of green ash in the wild that have remained healthy after emerald ash borer swept through the population. The possibility of these trees possessing genetic resistance to the beetle is being investigated with the hope that green ash could be restored using the surviving trees; the spread of emerald ash borer was facilitated by the extensive use of green ash as an ornamental tree in the central U. S. following the loss of American elms in the 1950s-60s due to Dutch elm disease. That epidemic was the result of a similar overuse of elms in urban environments, leading to a monoculture that lacked any disease or pest resistance. Scientifically for green ash this is because modern cultivars utilized regionally were parented from sometimes only four individual trees selected for unique traits and male seedless flowering. Proclaiming a harsh lesson learned, cities like Chicago did not replace dead elms with a 1:1 ash:elm ratio. Instead, silver and sugar maples, honey locust, linden/basswood, redbud and hackberry, among others, were utilized during this recovery period and in new urban and suburban areas.
With these additional species, many cities were able to reduce the percent of ash and other species to much lower levels than during the Dutch elm disease era where from 56% to 100% of the trees were elm. Injections and spraying of ashes with pesticides has been used in city parks to protect valued trues from emerald ash borer. Record cold temperatures during the winter of 2018-19 are estimated to have killed as much as 80% of ash borer larva in the Upper Midwest. Both American elm and green ash were popular due to rapid growth and tolerance of urban pollution and road salt, so many housing developments in Michigan were lined from end to end with ashes, a result of which the beetles had an enormous food supply to boost their population well above Infestation thresholds; the tree was extensively propagated and sold by local nurseries. According to the American Nursery Industry, "Back in the late 1980s, Dr. Frank Santamour Jr. a research geneticist with the U. S. National Arboretum, proposed the 10-20-30 formula for diversity in the urban forest, limiting the plantings in a community to no more than 10 percent within a single species, 20 percent within a genus and 30 percent within a family.""
Many communities are using a more strict 5-10-20 rule today, because of the threat posed by emerald ash borer. The emerald ash borer proved to be a far worse and more serious threat than epidemics of the past such as chestnut blight and Dutch elm disease because those diseases spread at a slower rate, only affected one species, did not kill the trees before they could attain reproductive maturity. Many areas have banned the sale of ash seedlings in nurseries, although seeds may be sold as they are not a vector for the insect. Green ash is one of the most planted ornamental trees throughout the United States and much of Canada but Alberta, including in western areas where it is not native, it is widely planted in Argentina. It is popular due to its good form and resistance to disease. About 40% of boulevard trees in Edmo