11/16/2020

American Sweet Gum

The Ohio Chapter ISA continued efforts to advance responsible tree care practices through research, technology, and education while promoting the benefits of trees. This Tree-Of-The-Month is commonly known as the American Sweet Gum or the Satinwood, Redgum, Sapgum, Starleaf-Gum, or Bilsted, the Latin name of Liquidambar styraciflua.

The American Sweet Gum is a low-maintenance deciduous shade tree native from Connecticut to Florida and Missouri further south to Texas, Mexico, and Central America. It is also native from the Sierra Madre of Mexico into Central America's cloud forests to Nicaragua. The United States Department of Agriculture states that the American Sweet Gum is native to Ohio's southern portions along the Ohio River.

This tree's Genus name Liquidambar comes from the Latin words liquidus meaning liquid and ambar. The meaning of amber has two parts that produce a fragrant resin. Specific epithet styraciflua means flowing storax. The common name of Sweet Gum refers to an aromatic balsam or gum that exudes from wounds of the tree. The American Sweet Gum belongs to the plant family, commonly known as Altingiaceae.  The genus Liquidambar has 15 commonly known species worldwide. These 15 species are widespread and are commonly found in China, Korea, Thailand, Taiwan, Laos, Vietnam, Turkey, Rhodes(Rhodes is the largest of the Dodecanese islands of Greece), North America and Mexico, and down to Honduras. In cultivation, this tree can be found in warm temperate and subtropical climates around the world beyond its previously described native ranges.

The American Sweet Gum typically grows to 60-80' (less frequently to 120') tall with a straight trunk. This tree species require little pruning as it has a natural central leader form; with age, it may develop over extended lateral branches. The American Sweet Gum has the habit of a pyramidal tree in its youth, but it gradually develops an oval-rounded crown as it matures. The American Sweet Gum Glossy has long-stalked, deep green leaves (4-7" across) that have toothed margins. Each of the American Sweet Gum leaves is 5-7 pointed and has star-shaped lobes. The American Sweet Gum leaves are fragrant when they are bruised or crushed. The fall color of the American Sweet Gum can be incredible with layers of a brilliant mixture of yellows, oranges, purples, and reds. The American Sweet Gum branches and branchlets may have distinctive corky ridges. The American Sweet Gum non-showy, monoecious, yellow-green flowers appear in spherical clusters in April-May. The American Sweet Gum female flowers give way to the infamous gum balls, hard, spherical, bristly fruiting clusters to 1.5" in diameter. The American Sweet Gum gum balls mature to dark brown and usually remain on the tree through the winter, but can create clean-up problems and potential slip hazards during the general period of December through April as the clusters fall to the ground.

Planting Requirements

Spring planting is recommended as fall-planted sweetgum can occasionally suffer from dieback. In the wild, American Sweet Gum grows in bottomland areas with rich, moist soil but can tolerate various soil conditions. The American Sweet Gum tree does not do well when planted in locations where roots are limited in their development. American Sweet Gum grows best in soils that are moderately coarse to fine soils that are well-drained and slightly acidic (pH 6.1- 6.5). American Sweet Gum develops a deep taproot with numerous highly developed laterals on well-drained bottomland sites and a shallow, wide-spreading root system on poorly drained sites. American Sweet Gum is very intolerant to shade but will tolerate temporary flooding. It also tolerates high salt sites if protected from high winds.

Daily watering is necessary for the first few weeks following planting. After one month, watering should be reduced to two times per week and continue for one year. The establishment takes 6 to 12 months for each inch of trunk diameter. Larger trees benefit from irrigation during the second year, and after that, if site conditions become dry.

Property Maintenance and Public Safety

In pedestrian areas, fruiting clusters of American Sweet Gum must be cleaned up because they create unsightly litter and create human safety problems (for example, slip hazards by inadvertently stepping on a cluster or an individual gumball). Reportedly, growth regulator products can be applied to Sweet Gum trees by sprays or by trunk injections that may reduce the fruiting cluster and reduce the likelihood of gumball hazards.

Check with a local Ohio International Society of Arboriculture Certified Arborist for what cultivars will work in your location.

Cultivars

This tree species and its various cultivars are often sold and are available from nurseries throughout the Ohio region, and it transplants easily in the spring of the year. Check with a local Ohio International Society of Arboriculture Certified Arborist for what cultivars will work in your location.

• 'Brotzman #1' - Selected for its corky bark and winter hardiness.
• "Burgundy™ '- Good red to purple fall color, but may not be as winter hardy as the species
• 'Cherokee' is a virtually seedless clone reportedly hardy to USDA Zone 5b and patented in 1997 by Earl Cully of Illinois.
• Emerald Sentinel® sweet-gum (Liquidambar styraciflua 'Clydesform'): A narrow-pyramidal shape; grows 30 feet high and 12 feet wide. Fall color yellow-orange.
• 'Gold Star' - Variegated form of sweetgum with splotches of yellow over green.
• 'Golden Sun'- New leaves emerge pale yellow in spring, changing to green in summer and turning red in autumn. Golden-yellow stems
• 'Gumball' - A multistemmed, slow-growing selection with an oval shape. Shrub-like habit.
• 'Rotundiloba' is a seedless clone selected in North Carolina in 1930. Hardy to USDA Zone 6b. Leaves of this fruitless cultivar are lobed rather than pointed. This is the most commercially important selection of sweetgum.
• 'Moraine' was introduced and patented in 1980 by the Siebenthaler Company of Dayton, Ohio. It has excellent purple, red, orange, and yellow fall foliage, which starts in late September to early October and usually finishes by mid-November in most Ohio locations and has the zone hardiness of USDA Zone 5b.
• 'Lane Roberts'medium-sized tree with a broad, pyramidal, fairly open crown. Large, star-shaped, lobed foliage is glossy green in spring and summer before turning brilliant red and purple shades in the autumn. It does produce insignificant flowers followed by burr-like fruit clusters. The wood exudes a sweet-smelling resin when pierced, giving the tree its common name.
• Slender Silhouette sweet-gum (Liquidambar styraciflua 'Slender Silhouette'): A narrow, columnar form, growing 6 to 8 feet wide and 60 feet high.
• 'Oconee' Sweetgum - Fall leaves - Is similar to 'Gumball,' but it has a more rounded habit and better fall color.
• 'Palo Alto’-Moderate-growing deciduous tree with a narrow pyramidal growth habit. The young maple-like leaf has a slightly purple hue and reddish leaf stems. The leaves are somewhat smaller than typical of the species. In summer, the foliage is bright green, turning orange-red to deep purple in autumn. Small yellow flowers in the summer are inconspicuous but are followed by round, spiky fruits that make an intriguing feature. The bark is very distinctive in appearance with deep furrows and takes on a light grey hue as it matures.
• 'Silver King'-is a conical, deciduous tree that develops a dense crown on a pyramid-shaped frame. The star-shaped leaves are glossy green in color, with a creamy white variegated edge, turning shades of red, purple, and orange before falling with the frosts. In winter Sweet Gum 'Silver King' still brings interest with fissured and corky bark. Insignificant greenish-white flowers in spring are followed by spiny, green fruit ripening dark brown.
• 'Variegata' or 'Gold Dust' was discovered more than 100 years ago by the now-defunct Baker Nursery, Painesville, Ohio. This clone has leaves blotched, spotted, and streaked yellow.
• 'Worplesdon' -Long narrow lobes to the leaves, which turn yellow and orange in the autumn. It is reported to occasionally produces fruit.

Environmental Importance

Like many native insects and other biological components, the Luna moth (Actias luna) utilizes sweetgum as one of its larval host species throughout Liquidambar's native range in the United States and northern Mexico. The seeds of the American Sweet Gum are small outside the seed pod but are often eaten by many birds, ranging from chickadees to wild turkeys, and by squirrels and chipmunks.

Ethnobotany

The American Sweet Gum is one of the most important commercial hardwoods in the Southeastern United States, and its handsome hardwood is often put to a great many uses, one of which is a veneer for plywood. The American Sweet Gum wood has been widely used for many applications, including flooring, furniture, and home interiors. The gum obtained from genus plants has been used for various purposes, including chewing gum, incense, perfumes, folk medicines, and flavorings. Known in Europe for its medicinal and aromatic qualities, sweetgum has long been valued in the New World. It is documented that in 1519. Montezuma shared xochiocotzoquahuitl (sweetgum) balsam with Cortés. Its genus name, Liquidambar, comes from the Latin liquidus (liquid) and ambar (amber) and refers to the bark's aromatic resin. Pioneer families used sweetgum as it has been used through the ages: for healing wounds, chewing, incense and perfumery. The resin was used in manufacturing drugs, soaps, and adhesives during World War I and World War II. In the southern U.S., sweetgum is an important timber tree used primarily as a veneer for furniture. The heartwood is pink and is referred to as redgum. The white sapwood is called sapgum.

In Chinese herbal medicine, lu lu tong, or "all roads open," is the hard, spiky fruit of native sweetgum species. It first appeared in Omissions' medical literature from the Materia Medica, by Chen Cangqi, in 720 AD. Bitter in taste, aromatic, and neutral in temperature, lu lu tong is claimed to promote blood and qi movement, water metabolism and urination, expels wind, and unblocks the channels. It is an ingredient in formulas for epigastric distention or abdominal pain, anemia, irregular or scanty menstruation, low back or knee pain and stiffness, edema with difficult urination, and nasal congestion.

​Tree Selection Tips
The Ohio Chapter ISA recommends working with an ISA Certified Arborist when selecting or caring for any tree in your landscape. To better guide you on the vital plant information for the American Sweet Gum use our friendly user's guide below:

Written by Mark A. Webber BCMA, CPH, LTE,  MArborA, OCMNT, TRAQ, TPAQ

Literature Sources:

Bensky, D; Clavey; Stöger, Erich (2004). Chinese Herbal Medicine: Materia Medica. Eastland Press. ISBN 978-0-939616-42-8.  (Collected on November 12, 2020)

https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=c116

https://holdenarb.org/horticulture/plant-profiles/sweetgum/  (Collected on November 12, 2020)

https://www.uky.edu/hort/Sweetgum#:~:text=Selected%20cultivars%3A&text='Brotzman%20%231'%20%2D%20Selected,splotches%20of%20yellow%20over%20green.  (Collected on November 12, 2020)

Hsu, E.; Andews, S. (2005). "Tree of the year: Liquidambar" (PDF). International Dendrology Society Yearbook. 2004: 11–45. Archived from the original (PDF) on 2017-10-22. Retrieved 2020-11-12.

https://en.wikipedia.org/wiki/Liquidambar (Collected on November 12, 2020)

https://www.burncoose.co.uk/site/plants.cfm?CFID=b75bcfee-db6d-41df-af5b-79047d34ca30&CFTOKEN=0&pl_id=2570 (Collected on November 12, 2020)

https://www.frankpmatthews.com/catalogue/liquidambar(Collected on November 12, 2020)

https://plants.usda.gov/factsheet/pdf/fs_list2.pdf (Collected on November 12, 2020)

https://www.srs.fs.usda.gov/pubs/misc/ag_654/volume_2/liquidambar/styraciflua.htm    (Collected on November 12, 2020)

U.S. Department of Agriculture, Forest Service. 1965. Silvics of forest trees of the United States. H. A. Fowells, comp. U.S. Department of Agriculture, Agriculture 

Photograph sources Mark A. Webber 2020