American sweetgum听(Liquidambar styraciflua), also known as听American storax,听hazel pine,听产颈濒蝉迟别诲,听谤别诲驳耻尘,听蝉补迟颈苍-飞补濒苍耻迟,听star-leaved gum,听补濒濒颈驳补迟辞谤飞辞辞诲,听or simply听sweetgum,听is a听听听in the genus听听native to warm temperate areas of eastern听听and tropical montane regions of听听and听. Sweetgum is one of the main valuable forest trees in the southeastern听, and is a popular ornamental tree in听. It is recognizable by the combination of its five-pointed star-shaped leaves (similar to听听leaves) and its hard, spiked fruits. It is currently classified in the plant听听, but was formerly considered a member of the听.
Description
Size
Liquidambar styraciflua听is a medium-sized to large tree, growing anywhere from 15鈥�20听m (50鈥�70听ft) in cultivation and up to 45听m (150听ft) in the wild,听with a trunk up 60鈥�90听cm (2鈥�3听ft) in diameter, on average.听Trees may live to 400 years.听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.
Bark and branches
Another distinctive feature of the tree is the peculiar appearance of its small branches and twigs. The bark attaches itself to these in plates edgewise instead of laterally, and a piece of the leafless branch with the aid of a little imagination readily takes on a reptilian form; indeed, the tree is sometimes called "alligatorwood".听The bark is a light brown tinged with red and sometimes gray with dark streaks and has a density of 590听kg/m3听(37听lb/cu听ft).听It is deeply fissured with scaly ridges.听The branches carry layers of cork.听The branchlets are pithy, many-angled, winged, and at first covered with rusty hairs, finally becoming red brown, gray or dark brown.听As an ornamental tree, the species has a drawback鈥攖he branches may have ridges or "wings" that cause more surface area, increasing weight of snow and ice accumulation on the tree. However, the wood is heavy and hard with an interlocking grain,听but is difficult to season.
Leaves
The听听usually have five (but sometimes three or seven) sharply pointed palmate lobes.听They are 8鈥�13听cm (3鈥�5听in) wide on average and have three distinct bundle scars.
They are long and broad, with a听6鈥�10听cm (2+1鈦�4鈥�4听in) petiole. The rich dark green, smooth, shiny, star-shaped leaves generally turn brilliant yellow, orange, red, and purple colors in the autumn.听This autumnal coloring has been characterized as not simply a flame, but a conflagration. Its reds and yellows compare to that of the听听(Acer), and in addition it has the dark purples and smoky browns of the听听(Fraxinus).听However, in the northern part of its range, and where planted in yet 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听听or semi-evergreen, with negligible fall color. The leaves are 8鈥�18听cm (3鈥�7听in) broad with glandular serrate teeth. The base is truncate or slightly heart-shaped. They come out of the bud plicate, downy, pale green, when full grown are bright green, smooth, shining above, paler beneath.听They contain tannin and when bruised give a resinous fragrance.
While the starry five-pointed leaves of听Liquidambar听resemble those of some听听(Acer),听Liquidambar听is easily distinguished from听Acer听by its glossy, leathery leaves that are positioned singly (), not in pairs (opposite) on the stems.听听and听听caterpillars feed on the leaves.
Flowers
The flowers typically appear in spring and persist into autumn/fall, sometimes persisting into winter. They are typically about听25鈥�40听mm (1鈥�1+1鈦�2听in) in diameter and are covered with rusty hairs.听The flowers are unisexual听and greenish in color. Staminate flowers in terminal racemes 5鈥�8听cm (2鈥�3听in) long, the pistillate in a solitary head on a slender peduncle borne in the axil of an upper leaf. Staminate flowers destitute of calyx and corolla, but are surrounded by hairy bracts. Stamens indefinite; filaments short; anthers introrse. Pistillate flowers with a two-celled, two-beaked ovary, the carpels produced into a long, recurved, persistent style. The ovaries all more or less cohere and harden in fruit. There are many ovules but few mature.
Fruit
The distinctive compound听听is hard, dry, and globose,听25鈥�40听mm (1鈥�1+1鈦�2听in) in diameter, composed of numerous (40鈥�60)听.听Each capsule, containing one to two small听, has a pair of terminal spikes (for a total of 80鈥�120 spikes). When the fruit opens and the seeds are released, each capsule is associated with a small hole (40鈥�60 of these) in the compound fruit.
Fallen, opened fruits are often abundant beneath the trees; these have been popularly nicknamed "burr (or bir) balls",听"gum balls",听"space bugs", "sticker balls",听"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.听The seeds are about听6听mm (1鈦�4听in) thick, winged, and wind-dispersed. Goldfinches, purple finches, squirrels, and chipmunks eat the seeds of the tree.听The seeds stratify within 30鈥�90 days at 1鈥�5听掳C (33鈥�41听掳F) or soaked in water for 15鈥�20 days.听The long-stemmed fruit balls of听Liquidambar听resemble those of the听听or buttonwood (Platanus occidentalis), but are spiny and remain intact after their seeds are dispersed; the softer fruits of听Platanus听disintegrate upon seed dispersal. The long-persisting fallen spiked fruits can be unpleasant to walk on; sweet gum is banned in some places for this reason.听In abundance, they can leave a lawn lumpy. The winter buds are yellow brown,听6听mm (1鈦�4听in) long, acute. The inner scales enlarge with the growing shoot, becoming听13听mm (1鈦�2听in) long, green tipped with red.