Tree of the Month: American Elm - Colonial Spirit
American Elm Trees
Tall, slender, with wavy branches and a full crown, American elm trees once dominated American forests and towns alike. As a widespread native species, they have always been loved as massive, hardy trees that make a good place to set yourself under. In fact, one could argue the nation was founded under the most famous elm tree of all: The Liberty Tree, which stood in Boston, Massachusetts from 1646 to 1775. Despite their symbolic prominence, however, elm tree numbers today are lower than in the past.
Elms were one of the most important street trees until the early twentieth century, but after much of America’s elms were devastated by Dutch Elm Disease from the 1930s onward, they weren’t replanted when a specimen died. However, innovations at nurseries and through public research have led to new species of elm trees that are resistant to the disease. While elms are still a common forest tree despite Dutch Elm Disease, homeowners can contribute to bringing them back into towns and cities by choosing to plant cultivars that are resistant to the fungal infection.
Identifying an American Elm Tree
Ulmus americana, also called a white elm or American elm, can be found across the eastern half of the United States and southern parts of Canada. These trees prefer moist soil, but they will tolerate a range of soil types, including compacted and low-nutrient soil. This, in addition to drought tolerance, allows elms to thrive in a town or city environment.
Spotting an elm isn’t difficult when you know what to look for, since they have a very distinct body shape and style of leaf. The trees create a V shape as they mature, and their thin trunks tend to have a diagonal crisscross texture. These interlaced layers of bark create deep ridges as they grow older. As they get bigger and taller, the roots of an elm will buttress, rising above the ground at the base (though not as prominently as a cypress tree).
The leaves of an elm are characteristic as well: the simple, single-leaf structure has an asymmetrical bottom half, as if an animal took a bite of one side. The edges of the pointed, oval leaves have distinctive double serrations, with both big and small pointed “teeth.” The bright green leaves are some of the first to bloom in spring, and in the fall, American elm trees turn golden yellow before they drop their leaves for winter.
An American elm tree is a canopy tree and can reach a height of 60 feet or more on average, with a crown width of 40 feet or more. It’s a fast-growing tree, making it popular to plant in residential areas where a healthy tree can live up to and over 100 years.
Elm trees, as some of the biggest and most widespread, offer habitat to a range of native insects and wildlife that depend on the trees for food, reproduction, and shelter. Small mammals like squirrels, chipmunks, and opossums live in elms, as do birds like finches, chickadees, and woodpeckers. Many birds that eat insects are attracted to the caterpillars that live on elm leaves, while the survivors turn into moths that bats, frogs, and owls eat.
Dutch Elm Disease
Dutch Elm Disease (Ophiostoma novo-ulmi) gets its name from the discovery of the tree infection in the Netherlands in the early 1920s, where it was first recognized (and believed to be originally from Asia). By the time the fungus reached the UK and the US in the 1930s, it was unable to be controlled, and the disease wiped out millions of trees across Europe and North America. In the US, it is believed to have arrived on a shipment of contaminated logs from Europe, first being noted in Cleveland, Ohio, where it spread like wildfire throughout the continent over the following decades.
The fungal spores are carried by native bark beetles by moving from elm to elm. The fungus also spreads between infected trees by spreading between roots of neighboring trees. The close proximity of trees, whether in a forest, in a yard, or along a street, permitted a fast spread of the fungal infection. By 1970, tens of millions of American elms had been destroyed.
Types of American Elm Trees
In the decades following the infection, horticulturalists in private nurseries and in government departments worked hard to develop species of elms that would be resistant to the Dutch Elm fungal disease. Today, these are readily available to be purchased and planted in neighborhoods and woodlands across the country.
Choosing a disease-resistant cultivar to plant in your yard is one of the best ways to reintroduce the elm tree back into Nashville neighborhoods. Here, we’ll look at the Colonial Spirit cultivar of elm (Ulmus americana), as well as a shorter, American-bred hybrid variety of elm (Ulmus frontier). The biggest differentiators between these are the size and autumnal color of the trees.
Colonial Spirit Cultivar
The Colonial Spirit cultivar of American elm is prized for its resistance to Dutch Elm Disease. This particular type of elm was originally bred in a nursery, and it offers all the benefits of an American elm: a sturdy canopy tree that reaches heights of 60 feet on average with dense foliage in the summer and bare branches in winter. The Nashville Tree Conservation Corps has the Colonial Spirit elm available from Hale & Hines Nursery through our tree sale so that Nashville residents can incorporate this beloved species back into our city’s ecosystem.
Frontier Elm
The Frontier elm is an American-bred elm, the result of research led by the U.S. National Arboretum. This hybrid of European and Chinese elms is Dutch Elm-resistant and is shorter than an American elm. At a height of about 40 feet at maturity, the Frontier elm’s leaves turn a deep red color in fall, giving this a special place in a neighborhood canopy. We’re glad to offer this hardy tree through our tree sale as well.
Caring for Your Elm
If you have an elm on your property, whether it’s young or mature, proper care is the best way to ensure it will stay around for a long time. Having a certified arborist inspect your tree once a year will keep it in healthy, trimmed condition, with access to any necessary fungicides that will help it be more resistant to potential threats, including diseases like Dutch Elm, but also Elm Yellows (caused by an infectious bacteria-like organism) and beetle infections. Regular pruning and trimming will keep an elm’s long branches safe and secure as they grow and reach out year after year.
How Rare Are American Elm Trees?
Before the Dutch Elm Disease outbreak in the 1930s, the American elm was widespread and regularly planted. Since then, however, they’re less common, especially in neighborhoods, but not necessarily rare in general. With innovations in breeding elm species to resist the fungal infection, as well as good care of mature specimens, their numbers are steadily rising with every new planting.
What Is Interesting About the American Elm Tree?
Elm trees are a source of morel mushrooms! Morels are a favorite for sauces, grits, or risotto, while others like to sauté or fry the mushrooms alone. The morel fungus has a symbiotic relationship with elm trees in particular, as well as with ash and apple trees. In-ground fungal growth, known as mycorrhiza, helps break down nutrients in the soil for living tree roots to absorb, while providing structure for the soil and holding some moisture. When an elm dies, the fungus sprouts mushrooms at the ground’s surface to reproduce by spreading its spores. Wild mushroom foragers know that when they find a dead elm still standing, the wet spring to follow will likely produce a batch of morels to gather. Be very careful when mushroom hunting, however, since some morel look-alikes are toxic. Check out some of the HENOSIS mushroom farm products that we carry!
Elms and Nashville
American elm trees are an essential part of our city’s wooded ecosystem; these tall canopy trees provide shade in the summer while losing their leaves to allow sunlight through in winter. Planting elms in yards and along sidewalks is an important way that residents and neighborhoods can contribute to filling some open space or replacing old trees and those lost in natural disasters, whether to storm or disease.
Consider volunteering with the Nashville Tree Conservation Corps to help us plant trees and look out for their best interest around town. Learn more about volunteering with the NTCC, and visit our tree saleif you are in need of a native tree to plant locally! If you haven’t already, sign up for our newsletter to read more about trees in Nashville.