Posts tagged ‘tree care’

The Smithsonian Gardens Tree Collection: Proactive Management

Smithsonian elm tree

This American elm tree on the grounds of the National Museum of Natural History is over two hundred years old. Eric Long, photographer.

The Smithsonian Gardens Tree Collection currently consists of over 1,850 trees, approximately 1,400 of which are located on the downtown Washington, D.C. and Anacostia campuses.  These trees add beauty to our grounds, and they offer myriad environmental and health-related benefits.  Unfortunately, it seems that trees are constantly under attack by a host of problems, ranging from severe climate, to native and exotic pests and diseases, to damage from construction and development projects, to the tough urban environment in which they grow.  Once these plants become stressed, it’s more likely that they will suffer due to one or more of these issues.  In addition, as trees grow, certain structural defects can develop which may cause problems in the future, especially when severe weather events can exploit the inherent weaknesses in these defects.

For these reasons, we at Smithsonian Gardens take a proactive, rather than reactive, approach to caring for these green assets.  Oftentimes, defects, cultural stressors, or insect and disease infestations that have gone unnoticed for a time can be difficult, if not impossible, to reverse.  Therefore, a thorough health and structure assessment of these trees was completed at the end of 2014.  This assessment consisted of a top-to-bottom, 360 degree visual evaluation of each tree.  All defects and other potential issues were noted and assigned a rating based on the severity of the condition observed.

Tree Banding

Smithsonian Gardens staff band trees.

What we had at the end of the evaluations was a complete list of trees, their problems (if they had any), and recommendations for correcting anything of concern.  Based on the ranking system, we now have an organized and detailed list of what maintenance and tree care work is needed, with a clear indication of where we need to start.  This has enabled Smithsonian Gardens to find and fix issues before they become more serious, and gives us the ability to be proactive with our tree management.  It also gives us a better idea of how to budget for upcoming maintenance needs.  Prevention is the best medicine, and any time we can find and correct an issue before it becomes serious it allows us to keep our trees happy and healthy for many years to come.

-Greg Huse, Smithsonian Gardens Arborist and Tree Collection Manager

 

January 14, 2015 at 6:30 am 2 comments

Preparing Your Trees for Winter

Japanese coral bark maple

Japanese coral bark maple (Acer ) in the Mary Livingston Ripley Garden, next to the Smithsonian Arts & Industries Building.

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.)

Kean Hall Garden wrapped in burlap for winter.

The boxwoods in the Kean Hall Garden in Livingston, New Jersey wrapped up in burlap for the winter, 1955. Smithsonian Institution, Archives of American Gardens, Garden Club of American Collection.

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

November 19, 2014 at 7:27 am Leave a comment


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