A century ago, the streets and parklands of America were lined with stately Elm trees. Elms are loved for their graceful shape, with branches like spreading fountains, and their green leaves that turn gold in fall. They are ideal street trees because their upward arching limbs don’t interfere with traffic, requiring very little pruning to maintain clearance underneath.
Sadly, the American elm (Ulmus americana) fell victim to a devastating pathogen called Dutch elm disease, which spread rapidly throughout the country the same way the Emerald Ash Borer is killing our native ash trees today. Dutch elm disease was first noticed in continental Europe in 1910, and eventually spread throughout the continent killing millions of trees. It arrived in the United States in 1928, in a shipment of logs from The Netherlands to the Ohio furniture industry. Of the estimated 77 million elms in North America in 1930, over 75% had been lost by 1989.
The loss of so many street trees was a tragedy from which many towns and cities still haven’t fully recovered. A major challenge has been finding a comparable shade tree so ideal for lining city streets. Many cities and towns have turned to the Japanese Zelkova, a rugged survivor closely related to elms but resistant to Dutch elm disease. Zelkova tolerates urban conditions well and can be used as a street tree, because it shares the upward-arching growth habit that made American Elm so ideal. Zelkova has interesting bark, clean serrated foliage and good fall color. It has a spreading, upright branching, vase-shaped structure, with a compact crown shorter and more rounded than the American elm.
As the tree ages, gray-brown outer bark peels off, exposing an orangish inner bark. Medium green leaves turn to shades of yellow, orange, brown, deep red to reddish-purple in fall. Zelkova tolerates most soil types, but prefers deep, moist, well drained soils. It does well in full sun. Established trees are drought and wind tolerant, resistant to Dutch elm disease, elm leaf beetle and Japanese beetle.
Zelkova is a large tree; some varieties can reach 75 feet tall and wide at maturity, but 40-50 feet tall and wide is more common. “Village Green” Zelkova is a popular variety; an excellent shade tree with a spreading habit 40 feet tall and wide at maturity. “Green Vase” is a narrower, more vase-shaped cultivar ideally suited for street tree and driveway planting. “Halka” is similar, but faster-growing than “Green Vase”. “City Sprite” and “Musashino” are smaller Zelkovas, growing less than 20 feet wide, ideal for smaller spaces and lining driveways.
Most people scratch their heads when we mention Zelkova because it’s a little-known tree to the general public, however it’s well known to arborists and widely used by city street tree managers. Once you learn to recognize it you’ll see it everywhere, particularly along city streets. We think it will become much more popular in the coming years, as people seek a substitute for the wildly popular Bradford pear, sales of which will be banned in Ohio starting next year because of its invasiveness.
Steve Boehme is a landscape designer/installer specializing in landscape “makeovers”. “Let’s Grow” is published weekly; column archives are on the “Garden Advice” page at www.goodseedfarm.com. For more information is available at www.goodseedfarm.com or call GoodSeed Farm Landscapes at (937) 587-7021.