Appendices & Glossary - Botanical Research Institute of Texas

1314 APPENDIX TWENTY-ONE/COMMERCIALLY IMPORTANT TIMBER TREES OF EAST TEXAS
LIQUIDAMBAR STYRACIFLUA L. SWEETGUM
(HAMAMELIDACEAE, WITCH-HAZEL FAMILY)
Other Common Names: REDGUM, WHITEGUM, STAR-LEAVED GUM, ALLIGATOR TREE, BILSTED, SATIN-WALNUT
Form and Size: medium to tall trees to 41 m; trunk straight, tall, often free of branches on lower half, 0.6–1.5(–2.25) m in
diameter; crown often pyramid-shaped but commonly more rounded in the western part of the range.
Leaves: deciduous, simple, alternate; leaf blades to 19(–25) cm long and 12(–16) cm wide, deeply palmately 5–7 lobed, starlike
in shape, the lobes acuminate, marginally toothed, bright green and smooth above, paler and smooth beneath except
for a few clusters of hairs in the axils of the main veins, pleasantly fragrant if crushed, quite showy in fall, turning
yellow to orange, red, deep crimson, or purplish; petioles (4.4–)6–10(–15) mm long.
Buds: terminal buds 6–12 mm long, broadest near the base and cone-shaped, sharp-pointed at the tip, covered with shiny,
reddish-brown scales.
Flowers: unisexual, male and female flowers on the same tree (plants monoecious), appearing in spring, without sepals or
petals; male flowers in several tight green clusters on an upright stalk ca. 5–9 cm long, the clusters produced at the tips
of branchlets; female flowers tightly clustered at the end of a hanging stalk produced in the axils of newer leaves, the
stalk 2.5–5 cm long, the flower cluster 1.2–1.7 cm in diameter.
Fruits: fruits in hard, woody, light brown, globose clusters 2.5–4 cm in diameter, these clusters composed of many individual
small capsules, each ending in 2 curved, horn-like points and each maturing 1–2 winged seeds, the fruits maturing
in autumn and persistent in winter.
Bark: grayish-brown, thick, with deep fissures separating the narrow, scaly ridges; small branches often with irregular
corky wings.
Wood: sapwood (called sapgum in the lumber industry) white, frequently with a pinkish tinge, often discolored with blue
sap stain; heartwood (called redgum) gray to varying shades of reddish-brown, the darker grades frequently with
darker streaks of pigment (called figured redgum); dull yellowish to brown discolorations indicate early stages of decay
and should not be confused with figured redgum; wood hard, heavy, not particularly strong, with grain frequently interlocked;
growth rings inconspicuous. The wood is capable of taking a high polish and has sometimes been exported
as “Satin Walnut”; it has also been passed off as mahogany, rosewood, or circassian walnut.
Habitat: flood plains, low hammocks (= thickly wooded areas), swamps, riverbanks, fields, woodlands, often in successional
areas (the species is frequently a pioneer species in areas such as old fields and logged areas and can form dense
stands).
Range: mostly Pineywoods and eastern Post Oak Savannah in Texas, but also native west in Red River drainage to Lamar Co.,
widely cultivated further west; widespread primarily in the southeastern U.S. from CT south to FL west to TX and OK.
Principal Uses: this is the most important species in the U.S.A. for hardwood veneer production, with the veneer used extensively
in furniture, panels, baskets, boxes, crates, and cigar boxes. The gum (oleoresin) obtained from the bark is used
in soaps and cosmetics, adhesives, lacquers, incense, and as a flavoring in tobacco.
Historical Uses: barrels (slack cooperage), mine props, railroad ties, pulp, planing-mill products (especially trim), radio
and television cabinets; oleoresin used medicinally by Native American groups and settlers as an antiseptic and in
treating skin diseases and dysentery, and also as a natural chewing gum. During World Wars I and II, the oleoresin was
used as a base in the manufacture or soaps, drugs, and adhesives.
Other Significant Information: SWEETGUM is the leading commercial hardwood species in East Texas and one of the most
important hardwoods in the southeastern U.S. It also produces a gum (balsamic oleoresin), called American styrax or
storax, a thick, clear, brownish yellow, semisolid or solid with a distinctive odor. The resin is collected from the inner
bark by gashing the outer bark. The strikingly colorful foliage in fall makes this a widely used lawn and street tree. The
species is one of the most adaptable hardwoods in terms of site and soil differences. It can even be planted on the alkaline
black “gumbo” of the Blackland Prairie, though care must be taken to prevent iron deficiencies. One is taken aback
when encountering SWEETGUM in montane cloud forests on the Mexico-Guatemala border. SWEETGUM is but one example
of the numerous East Texas deciduous forest genera that show a floristic relationship between some isolated forests in
the mountains of Mexico and Guatemala and those in the eastern United States. This relationship represents a Middle
Miocene (15–14 mya) extension of deciduous forests and associated fauna (particularly amphibians) to the south during
a period of widespread climatic cooling (e.g,, Antarctic glaciation). Subsequently, during the Pliocene (5.3–1.8 mya)
and later, the climate warmed and dried, and other types of vegetation (e.g., prairie and dry area shrub communities)
spread at the expense of deciduous forest. As a result, the once continuous deciduous forests became fragmented—
many plants thus have a disjunct distribution.
Recognition in the Field: the alternate, simple, deeply palmately 5–7 lobed, ± star-shaped, fragrant leaves and woody globose
clusters (to 3 cm in diam.) of 2-beaked fruits are distinctive.