Elms (Ulmus sp.)

The dorm was conveniently located and designed very literally as an apartment block. Red brick, windows outlined in white-grey, medical students returning to their own beds before waltzing around patient beds, science students returning from the labs in the wee hours of the morning, eyes full of sleep and thoughts full of pipette tips.

And a little way outside, standing tall, is a majestic American elm tree (Ulmus americana), its branches arching gracefully to give it an umbrella-shaped crown. Given its size it must have been there for years now, sheltering generations of people from the sun, and less effectively the rain or snow, whilst they grabbed lunch at the carts. Its companions are a crabapple tree, a couple of oaks, and a whole lot of squirrels, one of which once cold-heartedly turned down my offer of a cookie, chocolate chip to boot. (No, I haven’t forgotten.)

american elm

Elms, as a genus, first originated 20 million years ago in central Asia, and have spread over most of the Northern hemisphere. For their pleasing shapes and shade, they’re often grown as ornamental trees. Elm wood is resistant to splitting due to its interlocking grain, and thus valued in making wagon wheel hubs and chair seats. Romans and Italians planted elms to provide support for their vines, and branches and leaves can even be used to feed livestock. Medicinally, the inner bark of the slippery elm (Ulmus rubra) is used as a nutritional supplement and demulcent (something that creates a soothing film over mucous membranes, relieving some pain and inflammation such as that from coughs or sore throats).

One characteristic of elms is their serrate leaves, usually asymmetrical at the base and marked with distinct veins running parallel from the central vein to the edges. Flowers are small, and in the case of the American elm, brown. Elms can often grow very tall. I suppose this gives them better access to the wind, which they need to help disperse their samaras (winged flat seeds). These seeds are often a fresh, pretty, green before they mature and turn brown, which allows them to participate in photosynthesis.

elm seeds

Perhaps the most common disease affecting elms is the Dutch elm disease, a fungal disease caused by microfungi of the Ophiostoma genus and transmitted by elm bark beetles. Interestingly, the way this disease kills elms is similar to viral pathology in humans. Rather than the fungus itself killing the tree’s cells, it is the elm’s reaction to the fungus that does it in. In attempting to prevent the fungus from spreading further, the tree plugs its own xylem, equivalent to their blood vessels, with cell distensions known as tyloses. Whilst this does prevent fungal spread, it also prevents leaves from getting water and nutrients from the roots, thus killing the tree. As a testament to the value of elms, scientists spent years developing disease resistant strains and fungicidal injections that could help save the trees.

Despite their rather banal colours, elms, and in particular this American elm, served as my calendar throughout the year. I loved watching the flowers and leaves emerge in the spring and turn dark green in the summer, rustling every so often. In the autumn they’d turn a lovely golden yellow that caught the sunlight in the most beautiful way, transforming into glowing chandeliers. When they browned and covered the ground, autumn was well under way. Finally its graceful silhouette featured in many of my photos in the winter, sometimes frosted with a layer of soft snow, and in storms surrounded by a cloud of snowflakes catching the light from the lamp nearby.

References

  1. https://en.wikipedia.org/wiki/Demulcent
  2. https://en.wikipedia.org/wiki/Dutch_elm_disease
  3. https://en.wikipedia.org/wiki/Elm
  4. https://en.wikipedia.org/wiki/Ulmus_americana
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