University of Washington Botanic Gardens

1)   Rhododendron luteum

• Also called Yellow Azalea or Honeysuckle Azalea.
• Despite the sweet perfume, the nectar is toxic. Records of people poisoned by eating the honey date back to 4^th century B.C.
• Cultivated both as an ornamental and as root stock.

2)   Laburnocytisus adamii

• Also known as Adam’s laburnum or broom laburnum.
• Considered a horticultural curiosity, some branches produce yellow flowers while other branches produce coppery-pink flowers.
• Located along Arboretum Drive south just south of the Sassafras.

3)   Paeonia Lutea var. Ludlowii

• A rare Chinese form of tree peony.
• Large saucer-shaped blooms appear in late spring in a beautiful clear yellow color.
• Avoid pruning except to remove large branches.
• Located along Arboretum Drive across from the Sequoias.

4)   Petteria ramemtacea

• Fragrant yellow flowers in early summer and tri-foliate leaves make this unusual plant resemble a shrubby golden chain tree.
• Native to Yugoslavia and Albania.
• This specimen is located along the east side of Arboretum Drive behind the Dove Tree.

5)   Sophora microphylla

• Known as the Kowhai tree in its native New Zealand.
• The blooms of the Kowhai are regarded as New Zealand’s national flower.
• All parts of the Kowhai, but particularly the seeds, are poisonous to humans.
• Located along Arboretum Drive

Most visitors experiencing the beauty of our historic Azalea Way flowering cherries from now through May probably have no idea of how intensive maintaining their health and prolonging their longevity truly is for the UW Botanic Gardens horticulture staff.   Just ask our Integrated Pest manager, Ryan Garrison. Ryan with staff support spends many a day throughout the year monitoring and controlling the numerous diseases and insect pests our 175 plus cherries are prone to suffer from. Our rainy climate doesn’t help one bit either, especially when dealing with our most notable disease during blossom time;  a fungus known as Cherry Blossom Brown Rot. Yucko!  The good news is any new cherries we plant need to show a reasonable level of resistance. The not so good news is many of our older earlier bloomers, the ones extremely susceptible to the brown rot fungus,  need to be protected with fungicide applications during their bloom period.  As with all of our pest issues, we start with cultural and mechanical control efforts before resorting to chemical controls. The following Integrated Pest management (IPM) program discusses our best management practices for the control of blossom brown rot.  If you are interested in planting cherries for your home garden, I’ve included a list of cherries recommended for our PNW climate, all have good to excellent resistance to blossom brown rot.

Cherry Blossom Brown Rot - causal fungal agent known as Monolinia fructicola. The fungus overwinters on infected twigs and dried fruit on the tree or ground.  The fungal spores are spread in the spring by wind and rain through the blossoms, causing twig dieback.  As part of the UWBG IPM program, moving toward our goal of eliminating the use of all synthetic pesticides is our ultimate goal.

IPM relies on many strategies to manage plant health care. 

• Proper ID of the pest and its life cycle
• Regular monitoring of the plants
• The use of physical, mechanical, cultural, and biological controls
• Chemical controls used as a last resort*
• Least toxic chemicals used

* All spray applications are in compliance with WSDA pesticide regulations.  Sign postings are located at all entrances and Graham Visitor Center. Spray applications are scheduled based on timing and weather. We do our best to apply when public are not present. For more information, pls contact, David Zuckerman at 206-543-8008 or dzman@uw.edu

The cherries are pruned in early fall  to remove infected twigs and improve air circulation.  Tree rings are given a fresh coat of mulch in the fall to bury any infected plant material that may be on the ground.  In our Cherry Replacement program we are only using cultivars that are resistant to Blossom Brown Rot.

Cherries recommended for the PNW:

• Prunus‘Berry Cascade Snow’
• Prunus ‘Kwanzan’ syn. ‘Sekiyama’
• Prunus‘Pink Flair®’
• Prunus‘Royal Burgundy’
• Prunus‘Shirofugen’
• Prunus‘Shirotae’
• Prunus‘Snow Goose’
• Prunus subhirtella var. ascendens
• Prunus x yedoensis ‘Shidare Yoshino’

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.

• 103 total volunteers working 417 hours!
• Representing 4 companies/corporations: AT&T, Japan Business Association, Microsoft, Nordstrom
• Completing 5 projects:
• AT&T – Holly Collection
• 3 truckloads of blackberry and weeds hauled out, roots and all!
• Native plant bed and holly berm weeded and mulched!
• Japan Business Association-Pacific Connections Garden, Siskiyou Slope
• Weeded over 1,100 linear feet of 8′wide pathways and hauled out 3 truckloads of weeds!
•  Microsoft – Pinetum
• Wheelbarrowed and spread over 36 yards of mulch covering over 30 tree rings and beds!
• Microsoft – Rhododendron Glen
• 7 truckloads of blackberry hauled out, roots and all!
• Nordstrom – Azalea Way
• Wheelbarrowed and spread over 5000 sq’ of mulch covering several north-end Azalea beds!
• NOTE: 1 truckload is apporximately 3 yards.

• Special thanks to our sponsoring partner,  The Arboretum Foundation – especially Cynthia Welte and Rhonda Bush and of course our other managing partner, Seattle Parks and Rec. Without you guys, Day of Caring wouldn’t be possible.

  

  Blackberry Galore in Rhododendron Glen

Microsoft staff laboring in the Pinetum

An expansion of the Azalea Way lawn path is proposed.

Historically the Azalea Way lawn path experiences 8-9 months a year that are very wet making access difficult. In 2009 a crushed rock path was added to the middle of Azalea Way from Boyer Parking lot to the Woodland Garden. The proposed improvement will add 700 feet of 6 foot wide crushed rock path from the Woodland Garden to the Lynn Street Bridge Trail.

Parks anticipates the construction of the path will take place over the first two weeks in September 2011. We will work in sections to minimize the impact on users.

The project is funded by generous donation from the Arboretum Foundation.

Thank you for your support and patience during this project. 

For more project information please contact:

Lisa Chen, Park Horticulturalist Seattle Parks and Recreation 206-233-3777 or lisa.chen@seattle.gov