American Elm Traditional Cache

American Elm. Cultivar? Big surprise to me: "What's this leaf?" Daughter-in-law: "Elm?" She was right! I gave up on elms decades ago.

American Elm

Ulmus americana, generally known as the American elm or, less commonly, as the white elm or water elm, is a species native to eastern North America, occurring from Nova Scotia west to Alberta and Montana, and south to Florida and central Texas. The American elm is an extremely hardy tree that can withstand winter temperatures as low as −42 °C (−44 °F). Trees in areas unaffected by Dutch elm disease can live for several hundred years.

A prime example of the species was the Sauble Elm,which grew beside the banks of the Sauble River in Ontario, Canada, to a height of 43 m (140 ft), with a d.b.h. of 196 cm (6.43 ft) before succumbing to Dutch elm disease; when it was felled in 1968, a tree-ring count established that it had germinated in 1701.

 Ulmus americana (American Elm) This tree at Longwood Gardens was planted in the 1930's and is the last American elm in the gardens (the others having been lost to Dutch Elm Disease). The picture was taken on May 22, 2004

For over 80 years, U. americana has been identified as a tetraploid, i.e. having double the usual number of chromosomes, making it unique within the genus. However, a study published in 2011 by the Agricultural Research Service of the USDA revealed that about 20% of wild American elms are diploid, and may even constitute another species. Moreover, several triploid trees known only in cultivation, such as ‘Jefferson’ , are possessed of a high degree of resistance to Dutch elm disease, suggesting the diploid parent trees, which have markedly smaller cells than the tetraploid, may too be highly resistant to the disease.

Classification

Ulmus americana was first described and named by Carl Linnaeus in his Species Plantarum, published in 1753. No subspecies or varieties are currently recognized within the species.

Description

The American elm is a deciduous hermaphroditic tree which, before the introduction of Dutch elm disease, commonly grew to > 30 m (100 ft) tall with a trunk > 1.2 m (4 ft) d.b.h. supporting a high, spreading umbrella-like canopy.

The leaves are alternate, 7–20 cm long, with double-serrate margins and an oblique base. The perfect flowers are small, purple-brown and, being wind-pollinated, apetalous.

The flowers are also protogynous, the female parts maturing before the male, thus reducing, but not eliminating, self-fertilization, and emerge in early spring before the leaves.

The fruit is a flat samara 2 cm long by 1.5 cm broad, with a circular papery wing surrounding the single 4–5 mm seed. As in the closely related European White Elm Ulmus laevis, the flowers and seeds are borne on 1–3 cm long stems. American Elm is wholly insensitive to daylight length (photoperiod), and will continue to grow well into autumn until injured by frost. 

Early photos of New England American elms, showing growth patterns, The New International Encyclopædia (1905) 

Ecology

The American elm occurs naturally in an assortment of habitats, most notably rich bottomlands, floodplains, stream banks, and swampy ground, although it also often thrives on hillsides, uplands and other well-drained soils. On more elevated terrain, as in the Appalachian Mountains, it is most often found along rivers. The species' wind-dispersed seeds enable it to spread rapidly as suitable areas of habitat become available. American elm produces its seed crop in late spring (which can be as early as February and as late as June depending on the climate) and the seeds usually germinate right away with no cold stratification needed (occasionally some might remain dormant until the following year). The species attains its greatest growth potential in the Northeastern US, while elms in the Deep South and Texas grow much smaller and have shorter lifespans, although conversely their survival rate in the latter regions is higher due to the climate being unfavorable for the spread of DED.

In the United States, the American elm is a major member of four major forest cover types: black ash-American elm-red maple; silver maple-American elm; sugarberry-American elm-green ash; and sycamore-sweetgum-American elm, with the first two of these types also occurring in Canada. A sugar maple-ironwood-American elm cover type occurs on some hilltops near Temiscaming, Quebec.

Pests and diseases

The American elm is highly susceptible to Dutch elm disease (DED) and elm yellows; it is also moderately preferred for feeding and reproduction by the adult elm leaf beetle Xanthogaleruca luteola, and highly preferred for feeding by the Japanese beetle Popillia japonica in the United States. Trees grown in Europe have proven very susceptible to damage by leaf-feeding insects in general, far more so than Asiatic elms.

U. americana is also the most susceptible of all the elms to verticillium wilt, whose external symptoms closely mimic those of DED. However, the condition is far less serious, and the tree should recover the following year.

Dutch elm disease

Dutch elm disease (DED) is a fungal disease which has ravaged the American elm, causing catastrophic die-offs in cities across the range. It has been estimated that only approximately 1 in 100,000 American elm trees is DED-tolerant, most known survivors simply having escaped exposure to the disease. However, in some areas still not populated by the Dutch elm disease-carrying elm bark beetle, the American elm continues to thrive, notably in Florida, most of Alberta and British Columbia.

The American elm is particularly susceptible to disease because the period of infection often coincides with the period, approximately 30 days, of rapid terminal growth when new springwood vessels are fully functional. Spores introduced outside of this period remain largely static within the xylem and are thus relatively ineffective.

The American elm's biology in some ways has helped to spare it from obliteration by the Dutch elm disease, in contrast to what happened to the American chestnut with the chestnut blight. The elm's seeds are largely wind-dispersed, and the tree grows quickly and begins bearing seeds at a young age. It grows well along roads or railroad tracks, and in abandoned lots and other disturbed areas, where it is highly tolerant of most stress factors. Elms have been able to survive and to reproduce in areas where the disease had eliminated old trees, although most of these young elms eventually succumb to the disease at a relatively young age. There is some reason to hope that these elms will preserve the genetic diversity of the original population, and that they eventually will hybridize with DED-resistant varieties that have been developed or that occur naturally. After 20 years of research, American scientists first developed DED-resistant strains of elms in the late 1990s.

Fungicidal injections can be administered to valuable American elms, to prevent infection. Such injections generally are effective as a preventive measure for up to three years when performed before any symptoms have appeared, but may be ineffective once the disease is evident.

Cultivation

In the 19th and early 20th century, American elm was a common street and park tree owing to its tolerance of urban conditions, rapid growth, and graceful form. This however led to extreme overplanting of the species, especially to form living archways over streets, which ultimately produced an unhealthy monoculture of elms that had no resistance to disease and pests. These trees' rapid growth and longevity, leading to great size within decades, also favored its horticultural use before the advent of Dutch elm disease. Ohio botanist William B. Werthner, discussing the contrast between open-grown and forest-grown American elms, noted that:

In the open, with an abundance of air and light, the main trunk divides into several leading branches which leave the trunk at a sharp angle and continue to grow upward, gradually diverging, dividing and subdividing into long, flexible branchlets whose ends, at last, float lightly in the air, giving the tree a round, somewhat flattened top of beautifully regular proportions and characteristically fine twiggery.

It is this distinctive growth form that is so valued in the open-grown American elms of street plantings, lawns, and parks; along most narrower streets, elms planted on opposite sides arch and blend together into a leafy canopy over the pavement. However, elms can assume many different sizes and forms depending on the location and climate zone, and the classic vase-like shape is far from the norm in naturally-occurring (as opposed to cultivated) specimens.

Wood

 A wooden hand plane made of American elm. 

The American elm's wood is coarse, hard, and tough, with interlacing, contorted fibers that make it difficult to split or chop, and cause it to warp after sawing. Accordingly, the wood originally had few uses, save for making hubs for wagon wheels. Later, with the advent of mechanical sawing, American elm wood was used for barrel staves, trunk-slats,and hoop-poles, and subsequently became fundamental to the manufacture of wooden automobile bodies, with the intricate fibers holding screws unusually well.

Pioneer and traditional uses

Young twigs and branchlets of the American elm have tough, fibrous bark that has been used as a tying and binding material, even for rope swings  for children, and also for making whips.

John Ostrander’s elm trees (planted in 1877, pictured here in 1953) arched over East Avenue for nearly a century.

The Cornell Daily Sun, Volume 55, Number 129, 22 March 1935 

Campus Elms Harbor Overalled Tarzans

Seven out-of-place Tarzans have been swinging dizzily from limb to limb on the beautiful old elms of the Quadrangle for the last four days. These men are not out for their dally dozen, however, but are busily examining the trees 'for evidences of the dread Dutch Elm disease, which has been depredating the elms in New York State for the last two years. , They also are Industriously cutting off the dead wood from the ninety year old elms. If any evidences of the Dutch Elm disease are found, that ls, if the inner cambium layer of the twigs is brown, then down will come one of the Quadrangle's mighty monarchs, to save the other trees on the Campus and in the vicinity.

In the 1960s, Dutch Elm Disease finally killed all the elms on Cornell's campus. In 1969, the grounds crew left one six foot tall stump in front of Willard Straight Hall to be a lasting reminder of the elms, affectionately known to Cornellians as the Stump. For a decade, students used the stump as a combination soapbox/message board, delivering speeches from atop the piece of wood and tacking posters to its sides. In 1975, a student group sawed down the stump in the middle of the night and ransomed it for charity. Unfortunately, though the grounds crew reattached the stump, vandals knocked it over again. The stump stayed down, never again to be raised. Today, the stump is memorialized with a plaque at the tree's original location.

Elms on Central Avenue, "Arch of Heaven", 1933

The cache is a tied in, camoed, "micro" pill bottle, that you have to push hard to open and close. Please BYOP and put everything back as you found it, including the rubber band around the log and the plastic bag zipped closed.

Parking is hard during the week, daytime at least. I usually park at the Botanical Garden Visitor center. Free at night and weekends, 1 hour free any time, but you have to print a tag to show that you don't overstay. It's a nice walk around Beebe Lake.