Liquidambar styraciflua

Liquidambar styraciflua, commonly known as the American sweetgum among other names, is a deciduous tree in the genus Liquidambar native to warm temperate areas of eastern North America and tropical montane regions of Mexico and Central America. Sweetgum is one of the main valuable forest trees in the southeastern United States, and is a popular ornamental tree in temperate climates. It is recognizable by the combination of its five-pointed star-shaped leaves (similar to maple leaves) and its hard, spiked fruits. It is currently classified in the plant family Altingiaceae, but was formerly considered a member of the Hamamelidaceae.

Names

This plant's genus name Liquidambar was first given by Linnaeus in 1753 from the Latin ('fluid') and the Arabic ('amber'), in allusion to the fragrant terebinthine juice or gum which exudes from the tree. Its specific epithet styraciflua is an old generic name meaning 'flowing with storax' (a plant resin).

The common name "sweetgum" refers to the species' "sweetish gum", contrasting with the blackgum (Nyssa sylvatica), only distantly related, with which the sweetgum overlaps broadly in range. The species is also known as the "redgum", for its reddish bark. However, the first mention of any use of the amber is described by Juan de Grijalva, the nephew of the governor of Cuba, in the year 1517.

Juan de Grijalva tells of gift exchanges with the Mayas "who presented them with, among other things, hollow reeds of about a span long filled with dried herbs and sweet-smelling liquid amber which, when lighted in the way shown by the natives, diffused an agreeable odour."

The species was introduced into Europe in 1681 by John Banister, the missionary collector sent out by Bishop Compton, who planted it in the palace gardens at Fulham in London, England. The tree is a symmetrical shape and crowns into an egg shape when the branches get too heavy after its first two years of cultivation. It is deeply fissured with scaly ridges. The branchlets are pithy, many-angled, winged, and at first covered with rusty hairs, finally becoming red brown, gray or dark brown. but is difficult to season.

They are long and broad, with a petiole. The rich dark green, smooth, shiny, star-shaped leaves generally turn brilliant yellow, orange, red, and purple colors in the autumn. However, in the northern part of its range, and where planted in colder areas, the leaves are often killed by frost while still green. On the other hand, in the extreme southern or tropical parts of its range, some trees are evergreen or semi-evergreen, with negligible fall color. The base is truncate or slightly heart-shaped.

While the starry five-pointed leaves of Liquidambar resemble those of some maples (Acer), Liquidambar is easily distinguished from Acer by its glossy, leathery leaves that grow in an alternate pattern, and not in pairs on the stems. Luna and promethea moth caterpillars feed on the leaves. "space bugs", "sticker balls", "spike balls", or "monkey balls".

The fruit is a multicapsular spherical head and hangs on the branches during the winter. The woody capsules are mostly filled with abortive seeds resembling sawdust.

Uses

Wood

thumbnail|Lumber

thumb|right|Harvesting redgum in [[Richland County, South Carolina, 1904]]

Sweetgum (Liquidambar styraciflua) is one of the most important commercial hardwoods in the Southeastern United States. Its wood is bright reddish brown (with the sapwood nearly white) and may have black grain in the heartwood; it is heavy, straight, satiny, and close-grained, but not strong. It takes a beautiful polish, but warps badly in drying. The wood has a specific gravity of 0.5910. It is too liable to decay for outdoor use. and is one of the most important materials for plywood manufacturers. It is used for furniture, interior trim, railroad ties, cigar boxes, crates, flooring, barrels, woodenware, and wood pulp. It is also used for veneer for plywood. The wood is very compact and fine-grained, the heartwood being reddish, and, when cut into planks, marked transversely with blackish belts. The wood is also used to make chopsticks for the East Asian market, as it has a naturally light color with appeal to certain segments of the Asian market.

Resin

The tree's gum resin, for which the tree is named, exudes from the bark of the tree when wounded.

Shikimic acid

L. styraciflua seeds may be a renewable source of shikimic acid.

Medicinal

Traditionally, sweet gum has been used in Chinese medicine to treat issues such as diarrhea, coughs, and skin sores.

Cultivation

thumb|A group of young sweetgum in autumn

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Liquidambar styraciflua is a popular ornamental and forestal tree, cultivated for its distinctive foliage and intense autumn colors. It is commonly grown throughout its native North American range as well as many other temperate parts of the world, including moderately high elevations in the tropics. It is highly regarded in Bogotá, Colombia. The species grows best in moist, acidic loam or clay soil, and tolerates poor drainage. It typically grows with other coastal plain species such as willow oak and sweetbay magnolia. Its salt tolerance is moderate. Chlorosis can develop on alkaline soil, especially where organic matter is low. Also, the American sweetgum tree does not grow well in shady areas.

During the late 1970s and throughout the 1980s, Sweetgums were a popular landscaping and street tree. Three varieties, Palo Alto, Festival, and Burgundy, introduced in the late 1950s by the Saratoga Horticultural Foundation in Palo Alto, California became popular in the urban landscapes of California because of their pleasing appearance, striking fall colors, and ability to grow quickly and thrive; however, as the trees matured, the damage caused by surface roots and the increased production of seed balls led to the tree being considered a nuisance and a liability. Thousands of trees would be removed and repairs had to be conducted on nearby structures damaged by roots. The Western Arborist published a study that concluded that Sweetgums accounted for the greatest number of trees causing damage; in the city of Alameda alone it was found that 69% of Liquidambars planted in the city were either damaging or beginning to damage nearby structures. It is now recommended that the trees be planted at least 15 to 20 feet from structures and that they should not be used as street trees.

Among the many cultivars of Liquidambar styraciflua are (those marked have gained the Royal Horticultural Society's Award of Garden Merit):

'Burgundy' – dark red to purple fall colors may persist through winter
'Clydesform' – columnar or narrowly pyramidal; slow growth to 9 meters; yellow-orange fall colors; also sold as 'Emerald Sentinel'
'Festival' – columnar; pale green summer leaves; bright fall hues of yellow, pink and red; less hardy than most
'Firehouse' - pyramidal; bright red fall color; defoliates early; little to no seed production
'Goduzam' – variegated; pink to red-purple in autumn; also called 'Gold Dust'
'Grazam' – pyramidal, with glossy leaves. Orange, red and purple fall colors
'Gumball' – dwarf shrubby cultivar seldom more than tall, with purple-red fall color
'Lane Roberts' ()
'Moraine' – upright, rounded form, fast growth, red fall color, hardy to −30 °C
'Palo Alto' – various shades of red in fall; best in California
'Parasol' – develops rounded crown; mature height 10 meters; deep red fall color
'Penwood' ()
'Rotundiloba' – sterile cultivar with rounded lobes on leaves, originally discovered in North Carolina in the 1930s
'Slender Silhouette' – very narrow columnar form
'Worplesdon' () – cutleaf cultivar with orange, red and purple fall colors

thumb|right|Sweetgum (red) in a natural park

The organizers of the September 11th Memorial in New York donated a grove of sweetgum trees to the Flight 93 Memorial in Shanksville, Pennsylvania.

Infection on Liquidambar styraciflua

The imperfect fungus Dicarpella dryina <small>Sutton</small> is a leaf parasite reported to occur on a wide range of host plants, including species of sweetgum (Liquidambar styraciflua <small>L.</small>). Limber and Cash reported that leaf spots produced by this pathogen on several different genera of forest trees were 2–5 mm diameter with regular margins. During the summer of 1994 in the Nacogdoches County area of Texas, a prominent leaf spot on sweetgum was widespread. Infected leaves had numerous necrotic lesions, each surrounded by a reddish halo. The lesions tended to merge resulting in large areas of dead tissue. Infection and fungal development of D. dryina were investigated on leaves of sweetgum using a combination of microscopic techniques. D. dryina infection on sweetgum has been associated with the disease red leaf spot. Results of this investigation indicate that D. dryina can penetrate leaf tissue directly, thus having the ability to initiate infection on both upper and lower leaf surfaces. In other regions of the U.S., sweetgum populations may not be as susceptible to local populations of this fungus.

Environmental stress factors may also be involved, as reports have indicated that herbicide application and chlorosis caused by iron deficiency may increase susceptibility of D. dryina. Tannins (a type of biomolecule found in trees to protect it from fire, insects, and bacteria) have been reported to occur in healthy tissue of a variety of plants including sweetgum. They may prevent pathogen invasion by inhibiting fungal enzyme activity. Although cells of healthy sweetgum tissue appear rich in tannins, these materials apparently were not effective in preventing fungal colonization by D. dryina.

Notes

References

Bibliography

External links

Interactive Distribution Map for Liquidambar styraciflua
University of Michigan – Dearborn: Native American Ethnobotany of Liquidambar styraciflua
Landscaping.about.com: American Sweetgum Trees