Phytophthora Resistant Port Orford Trials Underway in Washington Park Arboretum

February 7th, 2012 by UWBG Horticulturist

The future health outlook bodes well for what many consider to be our finest native conifer in the PNW, Chamaecyparis lawsoniana, Port Orford cedar and its many cultivars.   Port Orford cedars have been under seige for many years from its worst enemy Phytophtora lateralis, a soil-borne pathogen that is especially virulent in wet soils, and essentially spells a death-sentence to this majestic tree once its roots are infected. There is no cure, but there is a preventative practice known as plant resistance. Dr. Everett Hansen at Oregon State University has developed a Phytophthora lateralis resistant root stock. And now, thanks to the development and research labs of Monrovia, they have introduced into the trade numerous Port Orford cultivars grafted with the phytophthora resistant root stock. These grafted Port Orfords are known as The GUARDIAN Series .

Through a generous donation from Monrovia, the Washington Park Arboretum will be trialing 6 GUARDIAN Series Port Orford cultivars, as well as, the type species grown on its own root. We have chosen 5 known “hot-spots” (either cultured or symptomatic of phytophthora infested soils) throughout the arboretum. There are 2 specimens each of the cultivars and the type. We’ll be monitoring and reporting on their growth and health for a period of 5 years. Knowing the extensive research and development that has gone into The GUARDIAN Series Port Orfords, after the 5-year trial, I expect a 100% survival-rate. Stay tuned for periodic updates on this exciting plant trial study.

 

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Washington Park Arboretum Oaks Rescued

February 7th, 2012 by UWBG Arborist, Chris Watson

Along with the constant rain and drizzle, winter in the Pacific Northwest often brings the occasional wind and snow events.  Damage to trees (and caused by trees!) is inevitable following these storms.  While wind events tend to cause the most spectacular tree failures, snow loads have been known to fell their fair share of limbs.  Damage to Arboretum trees has been lower than expected during the course of the most recent snow; however, our evergreen oak collection in Rhododendron Glen took a severe hit.

A 60-foot Canyon Live Oak (Quercus chrysolepis) uprooted, damaging another Canyon Live Oak and a Huckleberry Oak (Quercus vaccinifolia). The structure and foliage of these evergreen oaks provides a unique feel to this area of the Arboretum.  Preserving these trees was a high priority as losing them would be a dramatic loss.  In fact, the large Canyon Live Oak and the Huckleberry Oak are listed among the best specimens in the city in Arthur Lee Jacobson’s Trees of Seattle.

The tall Canyon Live Oak has an interesting history, as well.  Plant records indicate that this tree was grown from seed collected by Carl English Jr., for whom the botanic garden at the Ballard locks is named.

After a careful inspection, no root decay or extensive damage was observed on the large Canyon Live Oak.  Through the use of ropes, pulleys and a tractor, the tree was pulled upright, and supported by cables to a nearby tree.  After carefully installing a couple of braces, or steel rods, the smaller live oak will be spared a severe pruning.  As for the huckleberry oak, a minor crack in the main stem will be supported with a cable.

News stories following winter storms are often portray trees in a negative light.  However, through proper care and maintenance, most trees can withstand our seasonal storms.  Sometimes, when given a chance, the trees that receive the brunt end of Mother Nature’s fury can be given a new lease on life.  After all, trees are not only a vital component of our urban forest; they are one of our regions defining characteristics.


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