American Sweetgum

Basic Information
Tree ID: 
46
Family: 
Altingiaceae
Genus and species: 
Liquidambar styraciflua
Variety: 
Rotundiloba
Description: 
Liquidambar styraciflua is known as the American sweetgum. It is a deciduous tree that can be found in southeastern U.S., as well as southern Mexico and Central America. The sweetgum is a fast-growing tree that develops a significant taproot that tolerate high moisture levels in soil. It is used for its lumber, and is one of the most common sources of hardwood and plywood, but also produces spectacular colors as it drops its leaves in the fall. The sweetgum is a monoecious species and is pollinated primarily by wind. The sweetgum produces a resin that can harden and be used for chewing gum as well as medicinal purposes. Some other fun facts about the American sweetgum include that it provides protection and food for many forest animals, including squirrels, deer, doves, and chipmunks. It can be especially resistant to attack by insects, which makes them very helpful trees in reforestation projects and reclamations of former mineral mines. Finally, sweetgum trees can fix nitrogen and promote soil health. Our American sweetgum is situated in a beautiful green area between OML and Kroon Hall. It offers a calming presence in the heart of the science buildings at Yale, and is surely a special tree to observe, especially in the autumn.
Surveyors: 
Peri Shamlian, Ann Sarnak
Location
Area: 
Prospect and Sachem
Collected Data
Tree shape: 
Spreading, open, pyramid
Date of tree entry: 
03/03/2016
Height: 
8.53 m
Diameter at breast height: 
0.23 m

Bark
The bark of the American sweetgum is a gray-brown color, and becomes more and more ridged/fissured with increasing age. Ridges tend to form definitively for trees at about 25 years old. Younger trees, on the other hand, tend to have smoother bark, and occasionally displace cork-like projections, as shown in the picture.
Twigs & branches
Young twigs and branches of the sweetgum have characteristically corky ridges on which the fruits hang. The trunk of the sweetgum is rather straight; in small trees, branches protrude to create a pyramidal form and are small in diameter, while once the tree has aged, dominant branches emerge and their diameters expand. Branches tend to droop a bit and can carry small thorns, and the twigs themselves tend to be red/brown colored. If sweetgum blight develops, then the ends of those branches infected (usually toward the top) die. The twigs and branches are quite break-resistant.
Foilage
The fall foliage of the American sweetgum is quite spectacular, as shown in the picture to the left; leaves can be yellow, orange, red, and even purple during late October and November before leaves are dropped for winter dormancy in December. Sweetgum leaves tend to have 5 lobes, arranged in a star-like shape, with palmate venation (which means that each vein has roughly the same size through each lobe). Each leaf blade tends to be 4-8 inches, and the edges are serrated, meaning slightly jagged/notched around each leaf's border.
Reproductive Structures
The flowers of the American sweetgum bloom from March to May, and since the species is monoecious, the trees contain both pistillate and staminate flowers, but each flower contains one or the other sexual reproductive parts (i.e., a single flower doesn't have both pistil and stamen). The flowers tend to sit on higher up branches. Male flowers tend to sit above the leaves, while female flowers tend to hand below them. Male flowers can fall to the ground, while female flowers will usually stay on the tree, with specialized tube structures with sticky surfaces so as to catch the pollen which is dispersed by wind. The female structure is what hardens up into what are colloquially known as "gum balls," discussed further in the following section on sweetgum fruit. Sweetgum trees only begin to flower at maturity around 20-30 years old.
Fruit
The "gum balls," as described above, develop from female flower when they dry up and fall to the ground. They tend to be about 1.5 inches in diameter and are yellow/green while still on the tree and dark brown in color once they fall, usually dropping in late winter/early spring. These fruits can litter the ground and are sometimes understood as a safety hazard. L. styraciflua "Rotundiloba" is the name of a cultivar (specially/selectively breeded sub-species) of sweetgum that actually does not have these fruits.
Seasons
  • Sweetgum in Fall
  • Sweetgum in Winter
  • Sweetgum in Spring
  • Sweetgum in Summer
Research
Natural range of distribution: 
Habitat: 
The American sweetgum is primarily distributed in the eastern and southern regions of the United States. It grows in Connecticut (obviously!), but can grow as far south as central Florida and eastern Texas, and as far west as Missouri and Oklahoma. The sweetgum is also found in central America, including Guatemala, Honduras, and Nicaragua. It is most populous in the American South, though, especially in the lower Mississippi Valley. The sweetgum tree can withstand a wide range of temperatures, given that winter temperatures in the Northeast can get below freezing and summer temperatures can near 100 degrees Farenheit.
Origin, history, and uses: 

The name Liquidambar styraciflua means “liquid amber” and styraciflua is in reference to styrax balsam, which is a kind of resin produced by the sweetgum that can be chewed for medicinal and recreational purposes. The American sweetgum is native to North America, and its genus has only 5 other species included. According to the Arbor Day Foundation, the first mention of the sweetgum in history came from the diary of a Spanish conquistadore in 1519, who watched a ceremony between Cortez and Montezuma, in which the “liquid amber” resin from a sweetgum tree was used. Indeed, in North American Indian medicine, the resin from sweetgum trees were used to treat several ailments, as well as for dental hygiene.  

The other uses of the American sweetgum include lumber, veneer, and plywood, as well as fuel and pulpwood. The sweetgum, which also provides the material for hardwood, is one of the most important trees for timber in the country. The reason for the sweetgum’s name is that early American pioneers used to peel the bark off of the tree and scrape the gum off of the bark, which was used as chewing gum and also another resin derivative from the tree is used in fragrances, pharmeceuticals, soaps and natural medicines.

The American sweetgum is often planted as a street tree in surburban areas, but it also can tend to form thickets within forests. The tree grows best in deep, moist soil (it can only tolerate very moderate drought), with a pH no higher than 7. There are several different popular cultivars of the sweeetgum, including “Burgundy” which is better adapted to the American South, “festival” with peach-colored foliage, “Moraine” which is best adapted to cold, and Rotundiloba, which has no fruit production.

Phenology: 
Mixed buds of the American sweetgum form in mid-September, and the tree drops its leaves in the fall, and goes dormant during winter. After dormancy, the small green flowers of the sweetgum begin to bloom from March to May. From March to April, meiosis occurs to produce haploid gametes, with pollen dispersal occurring afterward. This tree is monoecious, meaning that it has both staminate and pistillate structures in the same plant. These flower structures are quite flowers and can be easily damaged in the cold. Fertilization occurs in late spring, and winged seeds, formed within the mature fruit and inside "seed balls," are dispersed by the wind from September to November. Each of these seed balls can contain up to 50 seeds. Once the seed has germinated and the vegetative buds appear, there is a rapid growth of leaves, also during the spring time.
References: 

Arbor Day Foundation, “American Sweetgum Liquidambar styraciflua,” Tree Guide, Accessed April 19, 2016.

B.W. Wells Association, “News from Rockcliff Farm: Spring Flowers of the Sweet Gum Tree – Liquidambar styraciflua,” April 7, 2016, https://bwwellsassociation.wordpress.com/2016/04/07/spring-flowers-of-th….

Carolina Nature, “Sweetgum,” Accessed April 25, 2016 http://www.carolinanature.com/trees/list.html.

Cathy Heidenreich, “Sweetgum, Confederate Native Becoming Yankee Favorite,” Geneva Arboretum Association, New York State Agricultural Experiment Station, Accessed April 22, 2016 http://www.hort.cornell.edu/bjorkman/lab/arboretum/trees/sweetgum.html

E. Richard Toole, “Sweetgum Blight,” U.S. Department of Agriculture Forest Service Forest Pest Leaflet 37, April 1959, Accessed April 21, 2016, http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fsbdev2_043681.pdf

Edward F. Gilman and Dennis G. Watson, “Liquidambar styraciflua: Sweetgum,” University of Florida IFAS Extension, Accessed April 27, 2016 https://edis.ifas.ufl.edu/st358.

Lady Bird Johnson Wildflower Center, “Liquidambar styraciflua,” Native Plant Database, The University of Texas at Austin, Accessed at April 19, 2016 http://www.wildflower.org/plants/result.php?id_plant=LIST2.

Missouri Botanical Garden Plant Finder, “Liquidambar styraciflua,” Accessed April 20, 2016 http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=c116.

Natasha Gilani, “Uses for a Sweet Gum Tree,” SF Gates, Accessed at http://homeguides.sfgate.com/uses-sweet-gum-tree-44350.html.

Paul P. Kormanik, “Sweetgum,” USDA Forest Services, Northeastern Area State and Private Forestry, Accessed April 27, 2016 http://www.na.fs.fed.us/pubs/silvics_manual/volume_2/liquidambar/styraci…

Ray R. Hicks, Jr. and M. Reines, “The Phenology of Sweetgum Liquidambar Styraciflua,” Journal Series Paper No. 102 of University of Georgia College of Agriculture Experiment Stations.

The Ohio State University College of Food Agricultural, and Environmental Sciences, PocketGardener, “Liquidambar styraciflua,” Accessed April 27, 2016, http://hvp.osu.edu/pocketgardener/source/description/li_iflua.html

Virginia Tech Department of Forest Resources and Environmental Conservation, “Sweetgum,” Accessed April 27, 2016 http://dendro.cnre.vt.edu/dendrology/syllabus/factsheet.cfm?ID=53.

Media and Arts
"The Sweetgum Tree" by the Spanish band Nino Y Pistola

“gumballs” crunch beneath feet,

spikes prickle our soles 

they say it’s “litter” but it reminds us that these seeds will spread 

against the harsh conditions

the frost

the drought

the acid toxic the remnants of zinc and phosphorus

roots stronger than ever before, and soon within a generation 

spectacular flowers will show, if not now then we can imagine their brilliance for our children and our children’s children. 

our liquid amber will

one day

taste sweet.