The largest tree beyond my door, and one of the largest trees in the immediate neighborhood, is a sweetgum. It probably isn’t that old and there are larger trees around, but it is still about 2′ in diameter and roughly 90 to 100′ tall, with furrowed light gray bark dappled with patches of a white crustose lichen on its trunk and pale green lichen on its branches (not as luxuriantly lichen covered as nearby oaks). Young sweetgums growing in a field have a conical, Christmas tree shape, and sweetgums actually have several ties to Christmas (this article was originally written for December). A sweetgum’s canopy usually becomes rounded with age, as is the case with this tree, and lower limbs growing into utility lines have been cut occasionally, so most of its great boughs are high in the air. It is a very exuberant tree. Many years ago it was surrounded by a grove of small sweetgums, at least some suckers from large exposed roots, and more still sprout. Some of the limbs of the big sweetgum develop vertical shoots that look just like large saplings several feet tall, later bending outward. Sweetgums probably aren’t meant to have a spreading form, and this tree has long had open space on most sides. Large sweetgums often have limbs that angle upward a short distance, with limbs closer to vertical branching off from the ends, and I might have seen how this form comes about. One calm summer evening a few years ago I was standing by a window when there was a whooshing sound and a huge, leafy limb fell, almost on our residential powerline. The top has been snapped off by lightning or wind at least once. Recently large pieces of a partially dead limb have fallen and there might be more dead branches than usual after the prolonged drought last summer and fall. At one time there was a very large squirrel nest made of leafy twigs in the principal fork high in the canopy, and hawk pairs have seemed to consider nesting in late winter. Birds often perch at the very top and during the winter some pry seeds out of the prickly ‘gumballs.’ Virginia creeper climbs up the wide trunk. Sweetgums might seem commonplace, but they have ecological and historical depths now largely forgotten.

Sweetgums are probably very familiar. In many places they are one of the first and most abundant woody pioneers to sprout in abandoned fields, joining other early successional trees like loblolly pines, cedars, winged elms, and ashes. Sweetgums bear large star-shaped leaves with five (sometimes seven or three) sharp, triangular points with slightly serrated edges, on very long petioles (leaf stems), and are often clustered on short side twigs. Along the west wall of UNC’s Coker Arboretum there is an unusual specimen whose leaves have five rounded points, an example of the Rotundiloba or roundleaf cultivar, apparently discovered in North Carolina in the 30’s and sterile. This tree is the state’s largest roundleaf sweetgum (90′ tall), according to the NC Forest Service, and there are others in the Arboretum. When bruised a sweetgum’s relatively thick leaves give off a characteristic, resinous fragrance reminiscent of pines. The leaves alternate along relatively thick twigs, green to bronze when young, spotted with pale lenticels, pores that allow the woody tissues to breathe, and sometimes corky growths. These warty growths can grow into “wings,” like those along the more delicate twigs of winged elms, which also grow in open areas and young woods, but sweetgums usually have smaller wings, if any, and have more robust twigs and buds than elms. Sweetgum twigs are supposed to have star-shaped pith in cross section, but I haven’t seen this so far. The furrowed but relatively soft pale gray bark, up to an inch or more thick, is one reason for the rare common name alligatorwood. The big sweetgum has light gray bark, very light gray on the south side (I wondered if the color was due to lichen, but it looks like bare bark), while a smaller sweetgum nearby has darker grayish bark.

The big, glossy greenish to bronze-colored terminal buds and smaller lateral buds, covered in a few large hair-fringed scales, glint in the wane winter sun, and it is a sign of spring when they begin to swell outside my window. It feels like no sooner do these big buds open, leaving pale yellowish bud scales littering the ground, then the spent male flowers also drop. Each monoecious tree produces flowers of both sexes, the yellowish green clusters of male flowers form spheres on stalks about 1 ½” tall, held upright at the twig tips as the shiny, vaguely spidery new leaves begin to unfold, while the female flower clusters hang as spiky green balls, much smaller than the mature fruit, each flower producing up to two seeds. The two styles of each flower become long spikes or beaks on the gumballs.

The dark brown mature ‘spiny’ gumballs can be seen dangling high in the air against the bracing skies of winter. They could be confused with the light brown balls of windborne seeds hanging on American sycamores, but sycamores have unmistakable pale bark, brown and flaking low on the trunk, becoming dappled green and then stark white at the treetops. In early winter I hear bits of pale grit falling on the leaf litter, and I think this come from the sweetgum, but their seeds are actually dark and resemble tiny miniature ash keys. Gumballs carpet the ground and a neighboring driveway by late winter, and help develop calluses when walked on bare foot the rest of the year, though they eventually wear down to merely rough balls.

In the fall sweetgums are valued for color, with leaves turning light yellow, red, and purple, sometimes nearly black.

As pioneers, sweetgums dislike shade and put on height quickly to keep their place in the sun. They can grow up to 150′ tall and 5′ across or more. The NC Forest Service lists two champion American sweetgums, a 134′ tall tree at Merchants Millpond State Park and a tree 138′ tall, but with the same circumference, in Wilson County. There are two national champion sweetgums, in Virginia and Texas. Two large sweetgums near the corner of Lawson and Lincoln streets at NCCU might be the largest I have seen by some inches, and pretty large sweetgums are common in the bottomlands along Northeast Creek. Reportedly a sweetgum can live for 400 years.

Sweetgum has been known as liquidamber, bilsted, red gum, star gum, and American storax. Its scientific name is Liquidambar styraciflua, coined by Linnaeus in 1753; the generic name meaning “liquid amber” while the specific name means “flowing with styrax (storax).” Earlier, in 1686, English naturalist John Ray had termed it Styrax liquida. Depending on the system, sweetgums are in their own family or are classified with witch hazels, uncommon woodland shrubs that bloom in winter on steep hillsides above Northeast Creek and elsewhere in the Triangle.

Sweetgums of some kind have been around for at least 99 million years and once grew across the Northern Hemisphere, but today there are only three other species: L. orientalis in Turkey and two species in East Asia, L. formosana and L. acalycina. American sweetgums range from southwest Connecticut through much of Eastern North America, south to Nicaragua. According to the Tropicos floral database, sweetgums are known as tzo-te in Chiapas and Guatemala, quiramba in Guatemala, and liquidambar in Belize, Honduras, and Nicaragua.

The Spanish recognized sweetgum by its fragrance when they first encountered it in the New World. The Old World’s storax or styrax, a fragrant resin, was used in incense, perfumes, medicines, added to wine, and applied to hair but the source was mysterious in Europe, beyond vendors in places like Constantinople. Linnaeus gave the name Styrax to a genus of small trees, some found here, thinking that one of them was the source, but today classical storax (or rosemalles) is thought to come from Turkish sweetgums, originally harvested by Turkey’s Yuruks, a nomadic Turkic group. This traditional industry is reportedly endangered. Apparently the Turkish sweetgum was scientifically described only in the mid-19th century. In his first hand account of the 16th century conquest of Mexico conquistador Bernal Díaz del Castillo describes the feasts presented to Aztec emperor Motecuhzoma Xocoyotzin. Included were “three tubes much painted and gilded, which held liquidambar [apparently called xochiocotzoquahuitl in native Nahuatl, referring to the pinelike fragrance] mixed with certain herbs which they call tobaco.” After eating the emperor would inhale a little smoke and sleep, a reported effect of storax. The Spanish might have first encountered American storax used in incense a few years earlier further down the coast of Central America. Several years after the war in Mexico, Álvar Núñez Cabeza de Vaca encountered sweetgums growing near Appalachicola in Florida during the Narváez expedition.

American storax, also called copalm balm, was described as a heal all by 16th century Spanish herbalist Francisco Hernández de Toledo, who spent several years researching in Mexico and Central America. John Banister is credited with introducing sweetgums to Europe in 1681. In 1839 styrene was first distilled from storax, and about a century later styrofoam was made from polystyrene. Storax was used to treat illnesses such as dysentery during the Civil War. An American storax industry developed during WWI, but was subsequently abandoned in favor of cheaper storax from abroad, only to be reactivated around WWII when the supply from the Japanese-held Taiwan was cut off. Apparently the expertise was only retained in Clarke County in southwest Alabama, making it the center of the wartime industry. A sweetgum there produces only ½ to one pound per year, and the amount is supposed to depend on the amount of foliage and increases going south.

In recent times storax has been used in salves, adhesives, fragrance, perfuming powders, perfume fixative, soap, and tobacco flavoring. It has been smoked for sleep, chewed for sore throat, colds, diarrhea, ringworm, catarrah, and applied to sores, wounds, piles, etc. It was used to clear mucous, and as an anti-septic and anti-inflammatory. Sweetgum leaf essential oil is chemically similar to Australian tea tree oil. The inner bark was boiled with milk to alleviate diarrhea. The resin has long been a chewing gum and teeth cleaner. Storax (not necessarily American) is supposed to be a component of commercially available compound tincture of benzoin.

Sweetgumballs are or were painted and hung on Christmas trees. They could probably also be used in crafting and if nothing else cats chase them. Chinese sweetgum balls, apparently called lu lu tong in Mandarin and softer than our gumballs, are used herbally.

Sweetgums are a prominent source of lumber, with heavy and strong but not very flexible wood. After about 60 years trees develop reddish heartwood below the white sapwood. Sometimes the sapwood was sold as sap gum and the heartwood as red gum. Unesteemed “gum wood” was often called satin walnut or hazelwood and could even be passed off as exotic Circassian walnut, rosewood, and mahogany. The wood polishes and stains well and the heartwood can display interesting figures. Sweetgum has been used in furniture, indoor trim, veneer, flooring, crates, cigar boxes, toys. barrels, boats, chopsticks, woodenware, plywood, railroad ties, and for pulp.

Many bird species, squirrels, and chipmunks feed on sweetgum seeds, while beavers eat the bark. Larvae of a sweetgum bark beetle bore in living and dead wood. Many moths eat the leaves as caterpillars, including several common geometers (inchworms), luna moths, promothea or spicebush silkmoths, hickory horned devils (the impressive caterpillars of regal walnut moths), imperial moths, sweetgum leafrollers, and the large Paectes. The big, ethereal light green to yellowish, long tailed luna moth, once known as the pale empress of the night, is relatively common and its caterpillars can feed on several tree species, but their abundance seems to vary greatly across the Triangle. They seem to be abundant around Falls Lake; a few years ago I would often notice the large black barrellike droppings of caterpillars under sweetgums and look up to see the thick green accordion-shaped caterpillars with yellow markings hidden high overhead. Luna moths might also be common around NCSU. On the other hand I’ve seen few around Jordan Lake or in Chapel Hill and Durham, though sweetgums are common there too (but tuliptrees might be the more common deciduous pioneer in Chapel Hill).

Black walnuts are familiar yet very unusual and valuable trees, and quite rare growing wild around here. At Jordan Lake State Recreation Area’s Seaforth access there are several exceptionally large trees of various kinds, including a black walnut. It’s spreading boughs are shaggy with resurrection ferns, verdant green after rain, contrasting with the yellowish-green of the walnut leaves, and appear dead at other times. The walnut is partially hollow and has dead branches, so it seems precarious and I wonder if the raised water table and/or heavy summer foot traffic is harming it. There are several much younger walnuts nearby. Near UNC’s Friday Center there is a black walnut about 2′ across, with a plaque saying it sprouted circa 1880. Large walnuts line paths at Durham’s West Point on the Eno. There are a few walnuts in the Northeast Creek basin. A tall tree more than a foot across grows at the base of a moist northwest facing slope near tributary Burdens Creek. It is a mystery how it got there. A few miles away there are spindly but nut-producing walnuts growing wild by a road in Chatham County connected only to Durham and Wake.

Their large nuts, classified botanically as drupes, fall around October, later than acorns and hickory nuts. An unusual feature is their smooth, relatively soft, fragrant, yellowish-green changing to black, staining husks, resembling a lemon more than a nut such as a pecan. Last fall there were unusually few walnuts under the Burdens Creek tree, whether because of the drought or because production varies yearly. On the other hand smallish nuts covered the ground under the Chapel Hill tree last October, and squirrels were gathered when I visited.

Black walnuts have dark, regularly furrowed bark and are tall and narrow in forests but short and very broad without competition. Giants can grow to 150′ tall and 6′ across, but walnut wood is valuable, so valuable that trickery and poaching occurs, and many were cut. They have large pinnately compound leaves up to 2′ long and 6” wide, with 9 to 23 long-pointed and serrated leaflets in pairs, smaller at the ends of the leaf, and usually there isn’t a leaflet at the tip. The leaflets have very short stems (petiolules) and the compound leaves alternate along the twigs. There is some hairiness on the underside of the leaflets and the leaf stem, called a rachis. Broken leaves and husks have a distinctive smell, lemony to me. Their leaves turn yellow early, contrasting with the dark trunks.

Several trees have similar leaves. White walnuts or butternuts, native in the Smokies, and introduced here, have oblong nuts, fewer leaflets (but usually with a terminal leaflet), and while both walnuts have chambered pith inside their twigs, it is darker brown in butternuts. Both species have grayish buds and the leaves fall to reveal three-lobed leaf scars, but there is a hairy spot only in butternuts and their buds are elongated. Hickories, such as bitternuts and pecans, are in the walnut family, but typically have fewer leaflets per leaf, a terminal leaflet, buds covered in scales, pith without chambers, and their nuts are usually dehiscent, opening along sutures. Locusts and Ailanthus also have pinnate compound leaves but are often small trees with multiple trunks growing in open areas. Ailanthus have very large leaves and leaf scars, a distinctive smell, and are most common in built-up areas while black locusts are thorny and produce fragrant white pealike flowers in late April.

Black walnuts seem to like well-drained soil and usually grow far from waterways. They grow fast, but are long-lived and don’t like shade, and they have a way to preserve their sunlight.

Black walnuts produce wind-pollinated catkins before leafing, each tree having both sexes. The dangling male catkins are 3 – 5” long. The female flowers are in clusters of 2-5 near the twig tips. The male and female flowers open at different times, but self-pollination is possible. A sapling can produce nuts after only five years, but few until age 10 – 15. The huge nuts are covered in a smooth husk, surrounding a seed with very thick, irregular wooden walls. ‘Everyone’ eats the nuts, yet I often find many left under wild trees and it takes a lot of effort to get inside. Apparently walnuts need a long cold period to sprout, and squirrels can steal planted nuts.

Black walnuts are known botanically as Juglans nigra, the generic name being an abbreviation for Latin Jovis glans, the acorn or nut of Jupiter (it was said people once lived on acorns while the gods ate walnuts). The word walnut originally referred to Persian walnuts, and is supposed to be a combination of the Anglo-Saxon for Welsh or Celtic, signifying foreign, and nut, wealh hnutu, as opposed to hazelnuts. Walnuts are honored in many place names, such as Cary’s Walnut Creek.

An unusual feature of black walnuts is their allelopathy. The walnut near Burdens Creek grows in a mature deciduous forest, but is in a sunnier glade. Around now toothworts and other early wildflowers bloom around it, joined by pink redbuds, an understory tree in the pea family, and in summer other peas cover the ground. Legumes often carpet the ground under walnuts in summer. Black walnuts produce hydrojuglone, which oxidizes into juglone and washes into the soil, to poison competitors, though ash, legumes, etc. seem immune. Some soil bacteria seem to be able to live on juglone.

Despite poisoning other plants, walnuts are edible to many animals. Squirrels, white footed-mice, and chipmunks disperse the nuts. In winter rabbits and deer nibble saplings. On the other hand walnut is harmful to horses and fish. Many insects feed on walnuts, including a curculio weevil, woodboring beetles, the walnut lace bug, stinkbugs, and aphids. Walnut fruitflies are supposed to develop in the husks, but I haven’t seen any. Many lepidopterans consume walnut, including one small butterfly, the banded hairstreak. Moths include gigantic hickory horned devils (caterpillars of the royal or regal walnut moth), related imperial moths, luna moths, walnut caterpillars and other Datanas, monkey slugs, walnut sphinx moths, curved-tooth geometers (a relatively large dark brown moth common at lights around April or May), American dagger moths and relatives, salt marsh caterpillars, fall webworms, walnut shoot moths, and several more.

Walnuts have a lot of versatility for humanity. Nuts are gathered from the ground and the nutmeat can be eaten raw, ground into flour, or boiled for oil used for cooking, fuel, and as polish (butternuts are more famous for oil). The trees can be taped like sugar maples. The husks produce a dye used to color cloth and even hair, and as ink. Walnut is supposed to repeal bedbugs and other insects, and I have wondered if the husks could be used to treat wood. Pulverized nuts are used in abrasives, filters, tires, composted, etc. The beautiful smooth wood was also used in furniture, paneling, veneer, cabinets, carriages, sewing machines, appliances, musical instruments, and for both cradles and caskets. During wars it went for gunstocks and airplane propellers. Walnut resists decay, so it was used for rail fences and railroad ties.

The leaves and husks have been known to cause dermatitis, but there are many herbal uses. The bark was used for toothaches; husks were used for ringworm, external inflammation, and to cause sleep; leaves were used for insect repellant and reportedly for sunscreen; and various parts were used to treat gastrointestinal problems. Juglone could be useful as a sedative and cancer inhibitor.

Thousand canker disease is an emerging threat for walnuts, though still far from here. Unlike other new catastrophic forest maladies like emerald ash borer and laurel wilt, thousand canker disease is native to North America, but was apparently unknown in the East until it reached Knoxville around 2010, so black walnuts still lack resistance. Thousand canker disease is caused by a recently discovered fungus spread by the walnut twig beetle, native in the Southwest and Mexico. In fall 2012 the disease was found in Haywood County, bordering Tennessee, but it is not known to have spread elsewhere in North Carolina since. The disease is present in several Western states, but only four Eastern states. Butternuts are susceptible and also face a canker noticed in 1967, probably from Asia. So walnut is another wood to be careful about moving over distances.

Below is an article I wrote for the April issue of the Parkwood Inside/Out.

The rarest tree in Parkwood

The big tree between the Parkwood Athletic Association field and the Masjid Ibad Ar-Rahman mosque might seem unremarkable, the quintessential tree, but it is the only Eastern or Carolina cottonwood I know of in Parkwood. Until recently it was the only one I knew of anywhere, but a year or two ago I was at the intersection of 54 and 55 and realized that the tall tree beside a stream between Walgreens and McDonalds is a cottonwood, and I saw a cottonwood of some kind at the Rollingview area of Falls Lake. River Dave once told me there are some along the Eno River and closer afield at New Hope Creek. Next to Parkwood’s cottonwood there used to be a pile of ballfield gravel, which resembles rocks along the Eno, so I wondered if the cottonwood might have come with a load of gravel, but since there is another arone around, maybe it came from this area after all.

Cottonwoods (Populus deltoides) are real poplars (“tulip poplars” are in the magnolia family) and resemble famous relatives like quaking aspens. The name poplar might come from a Latin phrase, arbor populi, the people’s tree, and the deltoides probably refers to the leaf shape. Eastern cottonwoods have large, spade-shaped leaves ending in a long point and with hook-shaped serrated edges. The leaf petioles are long and compressed, and there are glands at the leaf end. With these long stems, the thick leaves flap in a breeze, making a lot of noise. The yellowish twigs have a lumpy profile and have a squarish cross-section where there is a lot of growth. The terminal buds are covered by 6-7 scales and are supposed to be sticky or resinous, but not fragrant. Cottonwood leaves fall early in the season and without much color. Cottonwoods put on height quickly, as much as 13’ their first year, getting about 100’ tall (but higher in the West), sometimes after only 15 years, and develop an ever spreading form similar to broccoli, as can be seen in Parkwood. Our cottonwood has a stout trunk with strong branches starting near the ground and sweeping around, ending in twigs with an upward turn like claws. Cottonwoods have thick bark, but young trees are not very fire-tolerant, one factor limiting where they could grow out on the prairies. As with many fast-growing trees, cottonwoods don’t live very long, only about a century.

Other poplars grow in NC, including swamp cottonwoods (P. heterophylla), but I think our tree is an Eastern cottonwood. The only other poplars I know of in Durham are the very columnar Lombardy poplars, European ornamentals planted in yards, and white poplars, naturalized European trees which have an overall white appearance and form thickets, such as the one behind the former Triangle Nursery.

Long, wind-pollinated catkins (thus the name necklace poplar) emerged on Parkwood’s cottonwood in early March, while the leaves were still in large, conical buds. Each tree produces only one sex of flowers. On female trees small cottony seeds mature later in the spring, and fill the air. Wind dispersal allows cottonwoods to find rare open ground, such as bare banks of streams. The seeds have to drift to suitable ground fast, because they don’t remain viable very long.

In tree-rich Durham, cottonwoods are just another deciduous tree, but they could be called a Laura Ingalls Wilder tree, and were valued out on the prairies, where they were one of the few large trees, usually growing near water. The outer sapwood is wide, whitish, and lightweight, while the heartwood is dark brown. Cottonwood is easy to carve, but inflexible and warps a lot when drying, so it is mainly used for crates, plywood, excelsior (shredded wood, like the mulch on the path to the Hidden Playground), matches, and paper pulp. Indians in the Midwest used cottonwood for poles and started fires with the roots, and reportedly teepees relate to the shape of cottonwood leaves and children played with various tree parts. Cottonwoods are planted as windbreaks and to reclaim mines.

Deer, beavers, rabbits, and mice chew on the twigs and livestock can eat saplings if hay runs out. One guide says tea of the inner bark was used as a “female tonic” and to relieve scurvy, and cottonwoods produce aspirinlike salicin. Purple finches and other birds and squirrels eat the buds and catkins. Bees sometimes harvest the pollen, though the trees don’t rely on animals for pollination. Mourning cloak and red admiral caterpillars might eat the leaves, but around here they have many other choices, so cottonwoods seem to have few herbivores. Cottonwoods frequently develop internal rot, creating cavities for owls and squirrels.

To find out about the black locusts blooming at Parkwood Lake Dam this month and the honeylocusts on the Tobacco Trail, check out my article in the April issue of the Chatham County Line) newspaper.

My article in the May issue covers catalpa trees, such as the southern catalpa on Revere Road and others blooming in a few weeks.