Plant Stewardship

Tree Care program Hazard tree removals Integrated pest management Planting news

Caring for the Arboretum Trees and Plant Collections

The Arboretum's plantings constitute one of the premier woody plant collections in the United States with nearly 4400 different kinds of plants. These plantings are displayed among trees of our native Puget trough hemlock-cedar forest zone. The retention of native trees is part of WPA's naturalistic landscape style. This style also poses special challenges and needs in providing for the care of both native and collected plants. The maintenance and care of these plants is closely tied to our mission of education, conservation, and display. Both University and City staff work hard in caring for the Arboretum's landscape. Conservation of the plant collections in this highly utilized facility includes management for insect and disease pests, weak and dead plant removal, hazard reduction, plant replacement, and landscape restoration.

The Arboretum employs a holistic approach to managing plant health problems, combining the use of carefully timed, least toxic control applications, cultural practices to improve plant vigor, and the removal of severely affected plants beyond restoration. Extensive monitoring and follow-up evaluations are a critical part of this work. Click here for more information about plant health care and the pest management program at the Arboretum.

The arboriculture program covers care and management of collection and native trees. The goal is to reduce potential hazards through inspections and preventive work, as well as conserving the plant collections. This work includes pruning and training for young trees, cabling and bracing to preserve scaffold limbs in large trees, pruning and removal. The effects of root rot diseases as large trees age are a major contributor to hazards and actual failures in the larger native trees, particularly big-leaf maples.

Tree Care program

Sonic Tomography at the Arboretum

The UW Botanic Gardens would like to thank Tree Solutions, Inc. for bringing the latest technology in tree risk assessment to the Washington Park Arboretum. Tree Solutions assessed three large native trees using sonic tomography, a device that measures sound waves to detect decay and other abnormalities in wood.

Tree risk assessment is a vital component of maintaining the urban forest. Visual assessments typically provide more than enough information, but what cannot be seen yields valuable information to the Tree Risk Assessor.

Healthy looking trees often have decay inside the trunk and limbs. The decay's extent and the tree's overall vitality determine management (pruning, cabling, removal). Traditional methods of assessing decay include sounding the tree with a mallet, using an increment borer, and drilling. The resistograph is a more sophisticated method which uses a fine drill bit and produces a printed record.

In sonic tomography, sound waves sent through the tree are measured by sensors placed around the assessed part. These waves feed into a computer, which analyzes the input to produce a color image that accurately depicts both healthy and decayed wood. This detailed information greatly helps to manage the Arboretum's main attraction…the trees!

Hazard tree removals

There are no removals scheduled at this time. For questions about tree removals, please contact David Zuckerman, Horticulture Staff Supervisor, 206-543-8008 or dzman@u.washington.edu.

Integrated pest management

Garden Loosestrife

UW Botanic Gardens received a $75,000 grant from the Washington State Department of Ecology – Water Quality Program Aquatic Weeds Management Fund for research on reducing the population of garden loosestrife, a noxious weed that is covering the shoreline properties of Lake Washington and Foster and Marsh Islands of the Washington Park Arboretum. Professor Kern Ewing is the Principal Investigator.

Garden loosestrife (Lysimachia vulgaris) is a Class B noxious weed in Washington State and King County. King County requires control of this weed, which establishes itself in wetland areas, is very aggressive and invasive, and is a serious threat to the native character of area wetlands. It spreads by rhizomes and seeds. The primary goal of the research is to lessen the population to a level at which UW Botanic Gardens' staff can manage this weed on an annual basis.

UPDATE: Arboretum Pine Mortality

Washington State Department of Agriculture entomologists have been monitoring for the Arboretum's pine collection for insects that appear to be linked to increased pine mortality in the Pacific Northwest.

The Arboretum first noticed pine decline in 2005 among its two and three-needle pines. For more information, click here for the Everett Herald's article, "Why are the white pines dying?" or click here for the New York Times' "Bark beetles kill millions of acres of trees in the West".

Dutch Elm disease in the Arboretum

Three large dead English elms with Dutch Elm disease (DED) have been removedfrom the Arboretum. Each tree was infested with the elm bark beetle, which is the vector for the DED fungus. While the Arboretum's elm collection is small, it includes the historic Washington elms (Ulmus americana) and the amazing Camperdown elms, both ofwhich are susceptible to DED. Horticultural staff are monitoring elms carefully for signs of infestation.

 

 

 

 

 

 

Planting and maintenance news

Pinetum Collections development

The Arboretum hortiucltural crew is continuing work in the Pinetum by the Arboretum's Newton Street entrance. Arborist Chris Watson is removing two poplars and one bigleaf maple in an undeveloped portion of the Pinetum that is also infested with ivy and other invasives. After clean-up, four large Taiwan cedars will be moved to the site.

Woodland Garden

Site prep continues for the planting of Frank Byle's maple collection.

 

 

 

 

 

 

 

For further information about stewardship of the Washington Park Arboretum, please contact WPA Horticulture Staff supervisor David Zuckerman at dzman@u.washington.edu

 

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