Posts filed under ‘Trees’
As we gaze around at the beautiful autumn colors that our trees are showing us, we’re trying not to think about the arrival of the cold and snowy weather of winter. However, arrive it will, and now is the time to prepare your trees for those coming winter months. Although all trees are potentially susceptible to winter injury, young and/or thin-barked, and broadleaf evergreen trees require the most preparation.
Excessively cold temperatures, wind, and quick temperature changes can cause drying, browning, and death of evergreen foliage. This problem is most prevalent on broadleaf evergreens such as rhododendrons, laurels, boxwoods, and hollies. To help prevent this damage, construct a barrier of heavy burlap, like a fence, to block drying winds from their prevailing direction. If the entirety of the plant is exposed, loosely wrap it in burlap. In either case, be sure to leave the top of the plant exposed so light and air penetration can still occur. In addition, it is important to keep watering your trees up until the time of the first hard frost. A 4-6 inch layer of mulch over the root zone will also help the soil retain warmth and moisture. (Remember not to pile the mulch up against the trunk of the tree.)
Another issue of concern, which is also caused by rapidly fluctuating temperatures, is sunscald. This occurs when the sun has warmed the trunk of the tree, and then that trunk is rapidly cooled upon sudden shading from a cloud, etc. This condition results in elongated, dried and cracked areas of dead bark. This can be prevented by wrapping the trunk with commercial tree wrap (available at most home and garden centers) or other light-colored material. This will reflect sunlight and keep the bark at a more consistent temperature. The wrap should be placed on the tree in the fall and removed in the spring, after the last frost.
Broadleaf evergreen foliage damage and frost cracks are influenced by many factors, including plant species, location, drainage, natural protection, and how well established a plant is in the landscape. There is no specific temperature at which damage occurs, but if the forecast calls for temperatures below the average seasonal low (29-33°F for Washington, D.C.), it is best to utilize the protection methods outlined above.
Tree branches can be prone to breakage from heaving snow and ice loads and by strong winds. Weakly attached, overextended and broken limbs should be pruned. Trees with an upright form, such as juniper, arborvitae, and clump birch, can be wrapped in burlap, or held together by wrapping the branches collectively with twine or rope. Any wrapping material should be removed in the spring.
When natural food sources grow scarce in the winter, rodents may feed on the young bark and cambial tissue of trees. Plastic tree guards or a cylinder of ¼” wire mesh placed around the trunks of young trees will help prevent this damage. Be sure to remove these guards once the spring has come so the tree does not wind up growing into them.
Trees possess an extraordinary ability to withstand severe winter weather, with some being more hearty than others. However, with proper care and attention, your trees should come through the winter ready to show off their new flowers and foliage for spring.
-Greg Huse, Smithsonian Gardens Arborist & Tree Collection Manager
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.
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
In the summer of 2013 a specimen lacebark pine (Pinus bungeana) at the National Museum of Natural History had been in decline for several months. An investigation by Greg Huse, Smithsonian Gardens arborist, found very large girdling roots growing just below the soil surface. In his report Lacebark Pine # 122 Evaluation at NMNH he determined there was little to no chance that the tree could be rehabilitated. Within two months of issuing the report the tree turned completely brown and it was clear that it need to be removed.
Or did it? Could the once stately pine on the corner of Madison Drive and 9th Street that formed the border between the Butterfly Habitat Garden and the newly established Urban Bird Habitat find a second life?
As a mature specimen of this slow growing pine the tree exhibited extraordinary exfoliating bark in a patchwork of white, olive, light purple and silver. The multi-stemmed trunk was a striking structural element in the landscape that would be a significant loss. Luckily, there was a way to save this feature and in doing so support wildlife enhancing the value and educational lesson of the space. The tree was the perfect candidate to become a snag.
By turning the soon to be rotting trunk and branches into a snag it gains a new purpose in the Urban Bird Habitat serving as a space for nests, nurseries, storage, foraging, roosting and perching for birds, small mammals, and other wildlife in the city.
Here is how we did it:
The garden is a dynamic landscape and one must be prepared to deal with the changes that nature brings. Through creative thinking the Smithsonian Gardens’ staff discovered a great opportunity to turn what could have been a significant loss to gardens into a valuable resource. Today many museum visitors stop to look at this unique tree along the National Mall. Most seems puzzled by its presence but their questions are answered by the Snag interpretive panel.
So what do you think? Does your garden have a spot for a snag? Please share your thoughts in the comments below.
-James Gagliardi, Smithsonian Gardens Horticulturist
Living with Wildlife: Snags – The Wildlife Tree from the Washington Department of Fish and Wildlife.
What is the history of the Christmas tree? As far as common historical accounts are concerned, it all started with customs of the ancient Egyptians, Chinese, Scandinavians and other cultures that displayed evergreen trees, boughs and garlands during the winter. These decorations were symbols of everlasting life and reminders of the growth of spring, and they were also believed to ward off evil spirits, ghosts and illness.
The Christmas tree tradition as we now know it is thought to have begun in Germany in the 16th century when devout Christians began bringing trees into their homes and decorating them. Early decorations included nuts, fruits, baked goods and paper flowers. It is a widely held belief that Martin Luther was the first person to add lights to the tree. During a walk home one evening, he was struck by the twinkling stars through the evergreen trees and decided to recreate that feeling at home for his wife and children by erecting a tree and decorating it with candles.
In the early 19th century, the custom of the Christmas tree began to spread to European nobility. It wasn’t until 1846, however, that the tradition gained widespread public adoption. In that year, the popular British royals, Queen Victoria and her German husband, Prince Albert, were sketched for The Illustrated London News standing next to a Christmas tree in Windsor Castle with their children. Being popular amongst the British people, the practice became very fashionable and soon spread to the east coast of the United States. Due to this rise in popularity, tree ornaments were manufactured in large numbers, and U.S. patents for electric tree lights (1882) and metal ornament hooks (1892) were issued.
With their increasing popularity and acceptance, along with readily available ornaments and electric lights, Christmas trees began appearing in town squares and other public places and became commonplace in private homes.
The most popular species of trees for the holidays are Scotch pine, Douglas fir, Fraser fir, balsam fir, and white pine. Although artificial trees are popular with some, growing, living trees clean the air and water, trap atmospheric carbon, and provide wildlife habitat. When they are ready to be discarded, they can be turned into mulch and recycled back into the environment.
-Greg Huse, Smithsonian Gardens arborist
As Abraham Lincoln once said, “We cannot consecrate-we cannot hallow-this ground. The brave men, living and dead, who struggled here, have consecrated it, far above our poor power to add or detract.” In honor of Veterans Day in 2010, Brian Thacker, a recipient of the Congressional Medal of Honor was joined by representatives from the Medal of Honor Foundation, the National Air and Space Museum, and many veteran Smithsonian staff and volunteers to dedicate The Medal of Honor Tree on the grounds of the National Museum of American History (NMAH). Traditionally, red oaks (Quercus rubra) lined the north side of the museum. However, over time many of these trees were lost. To fill in the spaces left by the missing trees, Smithsonian Gardens collected trees from placed of historic significance to the United States such as the Lexington Green, the Trail of Tears, and the Manassas Battlefield. Brett McNish, Supervisory Horticulturist with Smithsonian Gardens, originally had the idea to seek out these historic trees and in conversation with a close friend in the museum community came up with the idea for the Medal of Honor Tree.
The tree commemorates recipients of the Congressional Medal of Honor. This award was created on July 12, 1862 when the bill S.J.R. No. 82 was signed into law by President Lincoln. The law designated that Medals of Honor were to be “presented, in the name of Congress, to such non-commissioned officers and privates as shall most distinguish themselves by their gallantry in action, and other soldier-like qualities.” Following the establishment of the Medal of Honor, soldiers quickly began receiving the medals for their valiant efforts in battle. The largest number of Medal of Honor recipients in one day of battle (120) took place at the Battle of Vicksburg on May 22, 1863. Since its creation, 3,463 service men and women have received the Medal of Honor. A variety of individuals have received the Medal of Honor representing the complex fabric of our nation. Medal of Honor recipients include one woman (Mary Walker), eighty-seven African Americans, forty-one Hispanic-Americans, thirty-three Asian-Americans, and thirty-two American Indians. Since 1918, Medals of Honor can only be given to members of the U.S. Armed Forces. However, exceptions have been made in special circumstances. Sixty-one Canadians, for example, hold the Medal of Honor, many of them from actions in the American Civil War. While the Medal of Honor now must be given to a member of the U.S. Armed Forces, they do not have to be U.S. citizens. The most recent Medal of Honor was awarded to Captain William D. Swenson on October 15, 2013.
To dedicate the Medal of Honor Tree, consecrated ground from 16 battlefields relating to 11 different wars that the United States was involved in were collected and added to the soil at the base of the tree. McNish discussed the immense task of collecting soil samples from these battlefields: “My goal was to get at least one soil sample from every war the US fought. Then it came down to what was possible to obtain. I think I came close to getting most of them. It took me about six months to get everything.” The process of collecting the soil involved many helping hands from the USDA, Department of State, Department of Defense, the American Battle Monuments Commission, and others, along with “a hefty FedEx bill” McNish noted. He created little collection kits made out of heat-resistant plastic containers.
A number of interesting stories grew out of the soil collection project. The soil collected from Luxembourg was from General George Patton’s grave at the Luxembourg American Cemetery and Memorial. The soil from Iwo Jima had its own history; it had been previously been collected by a Marine who visited the island on a pilgrimage. The soil then made its way to numerous veterans who took a little of it for themselves. McNish received the remaining soil from a retired Air Force officer in an airport VIP lounge. Then U.S. Ambassador to the Republic of Korea, Honorable Kathleen Stephens, collected Korean War soil from the Pusan Perimeter, an area that witnessed some of the first fighting of the Korean War. Soil from Haiti was collected by a group of Smithsonian curators working on post-earthquake relief for Musée National d’Haiti (the National Museum of Haiti). Because of difficulties mail, obtaining soil from Afghanistan was very difficult. The soil went through numerous hands before it was finally spread under the tree by an SI employee who had just returned from a tour of duty in Afghanistan.
Since its planting in 2010, the Medal of Honor Tree at NMAH is decorated every Veterans Dhistoay with a large red, white, and blue ribbon with a yellow center to highlight its significance in remembering the sacrifices of our nation’s service men and women.
-Mattea Sanders, Smithsonian Gardens intern
When people walk through the landscapes of Smithsonian Gardens, they often take pleasure in the beauty and majesty of the trees that are found throughout. The large spreading canopies, colorful spring and summer blooms, and brilliant autumn colors make for a feast for the eyes. Although we take great pride in the appearance of the trees here at Smithsonian Gardens, we also manage them for the numerous benefits that they provide, many of which are often not recognized.
Urban trees provide myriad contributions to the areas where they grow. Some of those benefits include:
- Storm water runoff and flooding reduction. It has been found that trees absorb the first 30% of most precipitation events through their leaf systems, and up to another 30% can be absorbed and held by their root systems.
- Traffic calming. Research shows that tree lined streets have fewer and less severe traffic accidents than those with no trees.
- Reduction of air pollution. Tree crowns capture and trap air pollutants, including automobile exhaust gasses and particulate matter. The severity of asthma and other negative health impacts are reduced in the presence of trees.
- Carbon sequestration. Trees absorb and retain carbon, thereby contributing to the reduction of greenhouse gasses. A US Forest Service study found that the average annual carbon sequestration of urban areas in the U.S. is approximately 26 million tons totaling a $2 billion value.
- Lowering of air temperatures. Urban areas can become extremely hot, as all of the concrete, asphalt and other hardscapes absorb heat throughout the day. In areas with trees, air temperatures can be reduced by 3-10°F, and properly shaded neighborhoods can realize energy cost savings of up to 35%.
- Improve your health. The findings of one study show that areas that have many trees can lower blood pressure, have a calming effect on teens and adults with ADHD, and contribute to overall emotional and psychological health.
- Add to property values. Realtor based estimates of street tree versus non-street tree comparable streets show a $15,000-$20,000 increase in home or business value.
So, the next time you’re enjoying the trees here at Smithsonian Gardens, remember all of the wonderful and helpful things they’re doing for us!
-Greg Huse, Smithsonian Gardens Arborist and Tree Collection Manager
As parents, teachers, and students wrap up the first couple of months of the new school year. Smithsonian Gardens horticulturist Christine Price-Abelow thought it would be fun to highlight a few plants with names linked to education. Keep an eye out for these plants growing in the museum gardens on your next class field trip!
1. Chinese Scholar-tree (Sophora japonica)
Chinese Scholar-tree is also known as the Japanese Pagodatree. In its native country of China the Scholar–tree was often planted near Buddhist shrines, hence the name. However it is commonly used as a city or street tree in the United States. It has a moderate to fast growth rate and usually reaches a height of 40-60’ with a nice rounded crown. Sophora trees have a compound leaf which casts a light shade and they are very tolerant to heat, drought and pollution. They produce creamy white flowers in mid-July followed by a pod type fruit. This “educational” tree can be found on the west side of the National Air and Space Museum near the McDonald’s trailer and seating area.
2. Princeton Elm (Ulmus americana ‘Princeton’)
The next time you visit Smithsonian Gardens and the National Mall, be sure to look up at the large towering trees shading the walkways. A large percentage of this tree canopy is made up of American elms, specifically the ‘Princeton’ American Elm. As you know, most plant cultivars are named for people and places and the ever popular Princeton elm is no exception. The Princeton elm was first introduced in 1922 by William Flemer of Princeton Nurseries located near Princeton, New Jersey. The Princeton elm was originally selected for its resistance to Dutch elm disease and aesthetic beauty. There are many examples of the Princeton elm planted throughout the U.S. and they can be genetically linked to a 200+ year old American elm tree formerly growing at Princeton Cemetery near Princeton University.
American elms have a beautiful yellow fall color and make excellent shade trees. They are fast growing and reach a height of about 80’ with a spread of 50-60’. The Princeton cultivar is known for its disease resistance and large dark green leaves. They are also a great choice for urban landscapes. Plant your own piece of history!
Smithsonian Gardens is using Ulmus Americana ‘Princeton’ as a street tree and in the tree box planters surrounding the museums.
3. Pencil Cactus (Euphorbia tirucalli)
In keeping with our “Back to School” theme, our next featured plant is the pencil cactus. Though often referred to as a cactus, this plant is actually a succulent and a member of the Euphorbia family. The pencil cactus is native to Africa and India, therefore it is grown as a seasonal tropical plant or a houseplant in the Washington, D.C. area. This euphorbia’s distinctive round, rod-shaped branches that resemble the familiar school implement give the plant its nickname. They are very easy to grow and can be propagated by cuttings.
*A note of caution, you should always wear gloves when working around this plant; it exudes a milky, latex-type sap that can cause an allergic skin reaction for some people.
This plant can be found growing in a large container in the Ripley Garden.
-Christine Abelow-Price, Smithsonian Gardens Horticulturist