Archive for March, 2014

Hope for the American Elm

American Elm

The American elm at the intersection of Constitution Ave. and 9th St. on the grounds of the National Museum of Natural History. Eric Long, photographer.

Smithsonian Gardens manages the health and maintenance of 1,873  trees in the Washington, D.C. area. As you walk around the Smithsonian gardens and museums you may notice a common theme: many of these trees are mature specimens with historical context and connection to the museums they surround. This is extremely evident as you walk the grounds of the National Museum of Natural History, where the extensive American elm plantings bring us back to a time when Ulmus americana was the predominant street tree in America. In fact, the large specimen on the corner of 9th Street and Constitution Avenue predates the museum, which celebrated its centennial in 2010.

As Dutch Elm Disease (DED) has wiped out the majority of stately American elms throughout the U.S., we at Smithsonian Gardens work diligently to monitor and manage our trees in order to prevent the spread of this lethal disease.

NMNH, 1909. Smithsonian Institution Archives.

Center Market vendors outside of the National Museum of Natural History in 1909. Dutch Elm Disease wiped out many of the majestic elms that predate the museum. Image courtesy of the Smithsonian Institution Archives.

It is with this management strategy in mind that we carefully select replacements when elm trees at the Smithsonian need to be removed. When one of the younger elms on the north lawn of the National Museum of Natural History was critically damaged during a storm, we once again debated and discussed which “resistant” elm to replace it with. One of the best choices for a true Ulmus americana replacement is the ‘Jefferson’ Elm (Ulmus americana ‘Jefferson’), selected through the collaborative efforts of the National Park Service and the USDA’s Agricultural Research Service (ARS).

This tree was selected for its excellent DED resistance and the fact that as a true species, it exhibits the classic American elm form, unlike some of the resistant hybrids.

‘Jefferson’ elms leaf out earlier in the spring and maintain their green color better in the summer than other U. americana specimens. We were very lucky to receive this tree from the National Park Service as it is just becoming available in the commercial trade at this time, and can be difficult to find. The National Park Service propagates ‘Jefferson’ by cuttings from the original tree, located on the National Mall, and grows the seedlings for six years at its National Capital Region Nursery. It is a long process and a difficult one, as only about 5% of the cuttings live to become mature trees. Hopefully this selection will become more common in the nursery trade so that we can once again plant these majestic trees with confidence. Until that time, we are very thankful for the ongoing collaboration between the National Park Service and Smithsonian Gardens to ensure that the American elm still graces the Washington, D.C. landscape.

-Jonathan Kavalier, Smithsonian Gardens Supervisory Horticulturist 

March 20, 2014 at 2:22 pm Leave a comment

Orchid Oddity: Habenaria medusa

Anyone who’s seen specimens from the Smithsonian Orchid Collection knows that this most diverse and species-rich plant family can display truly bizarre yet strangely beautiful forms. Literally every day, some improbable flower comes into bloom in our greenhouses. But there is one plant that invariably causes jaws to drop when viewed in full bloom. Most onlookers agree it is among our most spectacular and prized orchid species in the collection.

Habenaria medusa

Habenaria medusa via eol.

Habenaria medusae is a terrestrial orchid from monsoonal habitats in Indonesia and mainland southeast Asia. Producing a basal rosette of leaves from a subterranean corm, the plant is fairly nondescript until it sends up a 20-inch inflorescence bearing ten to twenty or more truly astounding flowers. Most prominent is the outstanding lip, composed of finely dissected, radially arranged fringe reminiscent of Medusa’s head of snakes, from which it gets its name. One might ask why such a lip evolved in the first place; in this case it is still somewhat of a mystery. Thought to be moth-pollinated because of its white color, sweet evening fragrance and nectar spur, the deep fringe is actually a fairly commonplace feature of moth flowers. Though no one knows exactly why, something about these deeply fringed flowers acts as a highly effective attractant to moths.

Habenarias are known for being difficult to cultivate, intolerant of poor or chemically treated water, and needing a strict, dry winter dormant period. They rot easily if watered during their dry season. Despite its sensitive nature, the Smithsonian’s specimen has proven to be more amenable than most to cultivation and has bloomed three times since being purchased as a small bulb from a vendor from Singapore at the World Orchid Conference. This year the plant was selfed (pollinated with its own pollen) to create more seedlings of this delightful species and also crossed with a related species with a deep coral pink lobed lip in the hopes of producing flowers with a colorful medusa lip.

-Tom Mirenda, Smithsonian Gardens orchid specialist

Visit our orchids at the United States Botanic Garden’s exhibit Orchid Symphony, a collaboration between Smithsonian Gardens and USBG, now through April 27th, 2014!

March 10, 2014 at 7:00 am Leave a comment


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